AREF bypass capacitance on ATMega2560?

[rickman]

On 9/7/2013 11:32 AM, krw@attt.bizz wrote:

On Sat, 07 Sep 2013 10:00:51 -0400, rickman<gnuarm@gmail.com> wrote:

On 9/7/2013 4:24 AM, John Devereux wrote:
rickman<gnuarm@gmail.com> writes:

If your FPGA designs are expensive or power hungry, then you are doing
things you can't do in an MCU or you are not using FPGAs properly.
They don't need to use any more power than an MCU and in many cases
less. They certainly don't need to be significantly more expensive
unless you consider every dollar in your designs. At the very low end
MCUs can be under $1 and still have reasonable performance. For $1
you can't get much in the way of programmable logic. For $3 however,
you can get a chip large enough for a CPU (with math) and room for
your special logic.

I've never used an FPGA, microcontrollers have increased in speed faster
than my needs so far. So I can usually bitbang everything or use a
peripheral. I used PLDs for glue logic back in the day but that's it. Oh
and I bought a small xilinx dev kit which I got to make a led flash then
put in a drawer for 15 years.

So your use of MCUs is based on inertia?

It seems that the "when all you have is a nail..." argument is
prevalent on both sides of this discussion.

Nonesense. I constantly look for MCU solutions for my designs.

But could you give an example of your $3 one? Or a favorite?

A startup company called Silicon Blue came out with a line of FPGAs
targeted to the high volume, low power market that exists for portable
devices. They were preparing their second device family and were bought
by Lattice Semi. The first family was dropped and the second family is
the iCE40 (for 40 nm). They are very low power although smallish. The
largest one has 8 kLUTs, the smallest 384 LUTs.

Everyone has $3 parts, now. It's a matter of finding the FPGA that
fits the application. The line between CPLDs and FPGAs isn't very
sharp anymore and is mostly marketing. CPLDs go well under a buck.

I won't argue that. But I don't consider CPLDs in the same vein as
FPGAs, but you are right, the distinction is blurring.

Last winter I was looking at designing a very low power radio controlled
clock to run in one of these. They were still playing a shell game with
the devices in the lineup and the 640 LUT part I wanted to use was
dropped... The only real problem I have with these devices is the
packaging. Because of the target market the packages are mostly fine
pitch BGAs. Great if you are making a cell phone, not so great if you
are designing other equipment.

A very good point. I've beat up all of the FPGA supplier on exactly
this point. I can't use fine-pitch BGAs. Less than .8mm pitch is a
real problem, though with some arm twisting we can go to .5mm. The
business case for an FPGA hasn't materialized (it affects the entire
board design), though. There is always another solution.

You can get the 1 kLUT parts for under $3 and possibly the 4 kLUT parts.
It has been a while since I got a quote. The 1 kLUT part is big
enough for a soft core MCU plus some custom logic.

IMO, a soft core MCU negates the whole reason for an FPGA. You're
using *expensive* realestate to do what a cheap piece of silicon can
easily do. There is probably an application somewhere that makes
sense but I've always found a better/cheaper solution.

That is the sort of thinking that is just a pair of blinders. I don't
care if the real estate is "expensive". I care about my system cost.
Gates in an FPGA are very *inexpensive*. If I want to use them for a
soft core CPU that is just as good a use as a USB or SPI interface.

BTW, with MCUs Digikey will give you a realistic price quote. In the
FPGA world the distis never give you a good price unless you ask for a
quantity quote. I have gotten prices quoted to me that were half the
list price. FPGA companies play a different marketing game and have a
lot of room to negotiate in order to buy a socket.

"DigiKey" and "realistic quote" don't belong in the same sentence. For
any quantity catalogs just don't cut it.

Your opinion. I don't sell 100,000 quantities, so the prices I get at
Digikey are often competitive with the other distis. Certainly they
give you a ball park number for comparison purposes. The point is that
with FPGAs, *no one* gives you a good price unless you get the
manufacturer involved. That is one down side to FPGAs.

--

Rick

 

[rickman]

On 9/7/2013 12:32 PM, Joerg wrote:

rickman wrote:

You can get the 1 kLUT parts for under $3 and possibly the 4 kLUT parts.
It has been a while since I got a quote. The 1 kLUT part is big enough
for a soft core MCU plus some custom logic.



Got a mfg and part number? Or a Digikey link?

At Digikey search on iCE40. That will give you a listing of all the
parts. Looks like Digikey's prices are a little high, not just because
they are Digikey. The $3 figure I gave is from quotes I got from
Silicon Blue before they were traded through Digikey. Like I said, you
need to get a quote on any FPGA to find the "real" price.

BTW, with MCUs Digikey will give you a realistic price quote. In the
FPGA world the distis never give you a good price unless you ask for a
quantity quote. I have gotten prices quoted to me that were half the
list price. FPGA companies play a different marketing game and have a
lot of room to negotiate in order to buy a socket.


Yeah, the old haggle game. Beats my why they still cling to such
medieval sales tactics. The only other market where that is customary is
with used car salesmen.

They don't even know how much in business opportunity they are missing
because of this. Guys like me need pricing info here, this minute, right
now. If there is even as much as a label "Call" I usually move on.

I don't think it is all about the "haggle". I think no small part is
about doing what it takes to get the design in and deny the competition.
When you get quotes from Digikey web site they never even know you are
looking at their parts. Think of it as a live auction vs. sealed bids.
They prefer to be in the live auction.

--

Rick

 

[Joerg]

rickman wrote:

On 9/7/2013 11:10 AM, Joerg wrote:
rickman wrote:
On 9/6/2013 7:10 PM, Joerg wrote:

That is often the problem. Sometimes a buck fifty is the pain
threshold.
Not in this ATMega case, the 2560 is very expensive but comes with lots
of ADC and analog muxes and all that. Things that will cost extra
with a
FPGA solution and eat real estate.


For $3 however, you can get a
chip large enough for a CPU (with math) and room for your special
logic.


For $3 I can get a big DSP.

What "big" DSP can you get for $3? ...


For example, this:

http://www.ti.com/lit/ds/symlink/tms320c5535.pdf

I don't see it for $3. Did you get a quote for your project? TI says
it is $5 to $8 at qty 1k depending on the flavor. You still need to add
Flash.

1k qty is $3.67 at Digikey:

http://www.digikey.com/product-detail/en/TMS320C5532AZHH10/296-32741-ND/2749713

$3.02 with 12wks leadtime at Arrow:

http://components.arrow.com/part/detail/51425505S8988412N7713?region=na

ROM is included.

... It has been a while since I looked
hard at DSP chips, but I don't recall any I would call remotely "big"
for $3. The TI chips that would be "big" are the TMS6xxx line which
start somewhere around $20 the last time I looked and that requires all
memory and I/O to be separate. The smaller DSP chips that you can get
for the $3 range are not "big" in any sense and only a very few of them
include Flash memory. So you still need another chip.


It has tons of memory on board.

Yes, and many FPGAs have "tons" of memory on board although not for
$3... but then this isn't a $3 part either...

It is a $3 part. See above.

Even a "small" FPGA can run rings around a DSP when it comes to
performance. Usually "big" in DSPs means fast and when you want really
fast DSP you use an FPGA with all the parallelism you can handle. DSPs
can't touch FPGAs for speed, even with low power.


Most of the really powerful FPGA that I connected to or had to review
designs with them in there were painfully expensive.

Because you were looking at FPGAs that were "painfully" large I'm sure.
How many pins, 256, 400+...? 20,000 LUTs, 40,000 LUTs?

Sure, that's why I wrote "powerful". The less powerful ones have never
impressed me much but I have to admit that I haven't looked the last
five years. So, tell us, which FPGA can fully replace the above DSP for
three bucks and where could one buy it off the shelf?

It's the same with myself. For many assigments I could as well live on
East Rarotonga. But not for EMC or noise fixing jobs with larger
installations.

I'm confused. Are you saying that on most jobs you don't care where the
programmer lives and works? ...


Yes, on most but _not_ all. That's key.

So you could use FPGA instead of an MCU on most of your designs? I'm
still confused. Are you saying if you can't use a part on all of your
designs you don't want to use it on any?

No, what I am saying is the it doesn't matter much which parts I use (my
clients decide that anyhow) but that finding a programmer locally can be
important. Some projects will not really come off the ground if the
programmer isn't local. Or it can take forever.

... I think that is what you said, but it
sounds like you are trying to disagree with me.


I disagree with the statement "it doesn't matter where the worker is".
Because sometimes (not always) it does matter. And when it does, close
proximity is very important. Then you need to literally work
side-by-side. Done it many times.

Our local SW guy sold his horse ranch and moved out of California. Only
to Reno which is under 2h drive but that's already a bit far. And in
winter you might not get through the pass or can't get back home.

I have done many jobs remotely and it has *never* been a problem. If
debugging is needed in the field, that is not the same thing as saying
the developer has to be in the field. You are welcome to disagree on this.

I do disagree.

I can only remember one time where I iterated through design changes in
the field and that was actually a case where I could have done it all
remotely, but I was pleasing the customer to be there. Turns out he
wasn't initializing the design right and it was hard to detect.

Well, if you are standing next to a huge roaring engine and this, that
and the other subtle disturbance has to be ironed out it would be a
major problem if the programmer is three time zones away. You don't have
to believe me but that's how it is with some of my assignments.

Just like EMC jobs on large gear can simply not be done remotely. Which
is why I bought the Signalhound analyzer (fits into carry-on).

One big advantage to FPGAs is the ability to simulate at a low level. it
is very easy to emulate the I/O in an HDL simulation. I don't know how
they do that with MCUs, but in the FPGA world I've never had a problem.

That is undoubtedly true. Plus probably less in errata headaches.

[...]

I've used schematic based tools and both VHDL and Verilog. I've worked
with the vendor's tools and third party tools including the NeoCAD tools
which became Xilinx tools when Xilinx bought them.

If anyone tells you they only know one brand of FPGA you are talking to
an FPGA weenie. I find MCUs to vary a *great* deal more than FPGAs in
terms of usage. MCUs need all sorts of start up code and peripheral
drivers, clock control, etc, etc, etc. FPGAs not so much. They mostly
have the same features and most of that can be inferred from the HDL so
you never need to look too hard under the hood.

In short, there is a lot of FUD about FPGAs. Talk to someone who
doesn't buy into the FUD.


Yeah, maybe next time I need major logic we should talk. But better not
about politics

Yeah... Even if you need minor logic let's talk. I find the real
advantage to FPGAs is in the fact that I can do almost *anything* in
one. I don't need to add stuff unless it is very application specific
like the CD quality CODEC on my current production board. I could get
CD quality from an FPGA design, but it wouldn't be worth the work to
save a $3 part.

So far the next project on the books that will contain logic is 2nd half
of next year. It will need a 16-bit audio codec as well but we can use
an external chip for that, PCM29xx series et cetera. Would (probably)
even keep it external with a uC because the 16-bit ADCs on those aren't
very quiet.

Things quickly unravel when you start relying on real hardware that is
on uC but not on FPGA. Comparators, ADCs, analog muxes, for example.

If you really need it all on a single chip, then yes, you won't find
that on so many FPGAs although Microsemi has their Fusion line with
analog. My cash cow uses a single FPGA and a stereo CODEC. That was
smaller than any MCU design because the MCU would still require the
CODEC (CD quality) and some of the control logic and interface could not
be done with any conventional MCU. I had to vary the speed of the CODEC
clock via an ADPLL to synchronize it with an incoming data stream. I
don't know how to do that with an MCU and no logic. But I can do it all
with FPGA logic and no MCU.


Hmm, I was looking at audio interfacing just yesterday because I am
going to need that on one new project. There's plenty out there that
should be directly adressable via MCU. For me it's probably going to be
something from the PCM290x series but there's also SPI variants and so
on.

Anyhow, I am also going to need ADC and comparator, including muxes for
them, so this one will likely be a uC case again because otherwise all
this has to be added externally.

You do know that it is not hard to add an ADC to an FPGA? No need for a
mux if all the inputs can be connected to separate pins. It all depends
on the resolution you need. 8 bits is easy, 16 bits - not so easy.

Mine are never less than 12-bit, often 16-bit.

Last week I reviewed a design with some larger FPGA on there. What I
found fairly disgusting was how much they had to be babied with the
power sequencing. uCs don't have that problem.

If you want to work with the wrong device, then you will find it hard to
work with. There are still single voltage devices on the market. If
this was an old design, most likely it was a Spartan 3 or similar era
device when they (for still unknown reasons) used three, yes, count
them, *three* voltages on the FPGA. The 2.5 volt aux supply was there
solely for the configuration interface which was normally to a 3.3 volt
device! Only from Xilinx...

If this was a new device, then I guess they picked one based on
something other than ease of use, eh? Don't assume all FPGAs are the
same.


Well, this guy is a real expert on high-end FPGA and the project
requires stuff with tons of horsepower.

That's fine, just don't judge all FPGAs by the ones you have seen. If
the only MCU you had worked with were ARM 11s using 3 Watts and running
a cell phone down in 8 hours, would you think the PIC MCUs were the same?

Well, give us all here an example of a FPGA that can fully emulate a
TSM320 and costs $3

You are aware that there are Flash based FPGAs that don't require the
external Flash chip, right?


Same with uCs, since a very long time

You are missing my point.

I guess then I don't see your point. Flash is available on almost
everything nowadays.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Ulf Samuelsson]

rickman skrev 2013-09-06 23:12:

On 9/6/2013 4:33 PM, Joerg wrote:
rickman wrote:
On 8/22/2013 1:51 PM, Joerg wrote:
Tim Williams wrote:
"Joerg"<invalid@invalid.invalid> wrote in message
news:b7l1blFlu93U2@mid.individual.net...
I saw people
using 0.1uF and 0.47uF. The datasheet is silent about stuff like
that,
as usual.
It doesn't really matter.

However, not everyone knows that because they don't say much about
the
innards of the chip. It's my first ATMega case, or maybe the 2nd.

Finally gave up and bit the uC bullet? ;-)


Sometimes you need it. A while ago I even had a switcher design that
would have been totally impossible to do without a uC. But it does
raise
eyebrows if I request timers and port pins and MIPS, probably
because of
my analog background. "YOU want some of the uC resources? What for?"

Sounds to me like you need FPGA resources moreso than an MCU. Are you
using the ADC or DAC, guess so or are you using the reference for the
brownout or something else? DACs are easy in FPGAs, ADCs not as easy.
Otherwise FPGAs do everything an MCU does plus...


I nearly always need ADC capability. Not for the brownout, I never trust
anything on those chips for that, the POR/BOR/WDT goes external. FPGA
have some downsides, they tend to become large, expensive and sometimes
power-hungry when you need math capability or an MCU core.

If your FPGA designs are expensive or power hungry, then you are doing
things you can't do in an MCU or you are not using FPGAs properly. They
don't need to use any more power than an MCU and in many cases less.
They certainly don't need to be significantly more expensive unless you
consider every dollar in your designs. At the very low end MCUs can be
under $1 and still have reasonable performance. For $1 you can't get
much in the way of programmable logic. For $3 however, you can get a
chip large enough for a CPU (with math) and room for your special logic.


But the main
issue for many projects is people. If the client has the experts in
house like in this case, fine. But if not then one is better off using a
uC where one can find a programmer in nearly every town. This is one
reason I am often partial to the 8051.

Do you work in *every* town? I find if I need a skill, it doesn't
matter where the worker is. I also find FPGA design is pretty common
these days. If you are ever short on FPGA design skills, give me a shout.


Of course the beauty of FPGA is that the availability of very fast glue
logic. Most uC are sorely lacking in that domain.

Yes, the ideal chip would add a section of FPGA fabric to a conventional
MCU and vary the size just as they do the RAM and Flash. I think at
this point the problem is cultural. Most FPGA companies are all about
the big iron selling for $100 a chip min and the MCU makers don't
understand programmable logic. Xilinx and Cypress is good examples.
Zync is a very high end solution, great if it matches your problem. PSOC
is not a bad idea, but their idea of programmable logic isn't worth much.

Give me a good $10 MCU/FPGA combo and I'll design the world! In the
meantime I'll be using soft cores. They are a lot easier to program
than an MCU anyway.

That was available with the FPSLIC. AVR core with 5/10/40k gates.
Unfortunately the combination of features didn't make sense.

40 MHz AVR with only 36 kB SRAM.

It would have been much better with an ARM7 core
with an external memory bus.

Since it was implemented in a technology, and not shrinked,
it eventually become cheaper to use a softcore with
a standard FPGA in a fine geometry technology.

I came to the conclusion that an MCU company cannot compete with an FPGA
company unless the programmable logic part is only a small percentage of
the die.

It would make sense to have a 5 kgate FPGAs in a modern micro.

The Xilinx Zync and Altera SoC are nice tries, except that most
of the standard peripherals suck and it is still beyond the price
most customers I've seen are prepared to pay.


BR
Ulf Samuelsson

 

[rickman]

On 9/7/2013 1:59 PM, Joerg wrote:

rickman wrote:
On 9/7/2013 11:10 AM, Joerg wrote:
rickman wrote:
On 9/6/2013 7:10 PM, Joerg wrote:

That is often the problem. Sometimes a buck fifty is the pain
threshold.
Not in this ATMega case, the 2560 is very expensive but comes with lots
of ADC and analog muxes and all that. Things that will cost extra
with a
FPGA solution and eat real estate.


For $3 however, you can get a
chip large enough for a CPU (with math) and room for your special
logic.


For $3 I can get a big DSP.

What "big" DSP can you get for $3? ...


For example, this:

http://www.ti.com/lit/ds/symlink/tms320c5535.pdf

I don't see it for $3. Did you get a quote for your project? TI says
it is $5 to $8 at qty 1k depending on the flavor. You still need to add
Flash.


1k qty is $3.67 at Digikey:

http://www.digikey.com/product-detail/en/TMS320C5532AZHH10/296-32741-ND/2749713

Not the same part pal. You're trying to pull a fast one on me? Are we
talking about the TMS320C5535 with "tons" of memory or the TMS320C5532
with *much* less memory?

$3.02 with 12wks leadtime at Arrow:

http://components.arrow.com/part/detail/51425505S8988412N7713?region=na

ROM is included.

ROM is not Flash.. is it? Are you thinking in terms of a mask ROM?

... It has been a while since I looked
hard at DSP chips, but I don't recall any I would call remotely "big"
for $3. The TI chips that would be "big" are the TMS6xxx line which
start somewhere around $20 the last time I looked and that requires all
memory and I/O to be separate. The smaller DSP chips that you can get
for the $3 range are not "big" in any sense and only a very few of them
include Flash memory. So you still need another chip.


It has tons of memory on board.

Yes, and many FPGAs have "tons" of memory on board although not for
$3... but then this isn't a $3 part either...


It is a $3 part. See above.

No, you need to pick a part number and stick with it.

Even a "small" FPGA can run rings around a DSP when it comes to
performance. Usually "big" in DSPs means fast and when you want really
fast DSP you use an FPGA with all the parallelism you can handle. DSPs
can't touch FPGAs for speed, even with low power.


Most of the really powerful FPGA that I connected to or had to review
designs with them in there were painfully expensive.

Because you were looking at FPGAs that were "painfully" large I'm sure.
How many pins, 256, 400+...? 20,000 LUTs, 40,000 LUTs?


Sure, that's why I wrote "powerful". The less powerful ones have never
impressed me much but I have to admit that I haven't looked the last
five years. So, tell us, which FPGA can fully replace the above DSP for
three bucks and where could one buy it off the shelf?

Lol, I don't know where you are coming from now. You don't like the
large FPGAs because they use power like they are... well, large. You
don't like the small FPGAs because they are, well... small.

When you stop using terms like "powerful" and want to actually consider
an FPGA for a design I can help you. Gut feel is nice as long as it is
based in fact.

It's the same with myself. For many assigments I could as well live on
East Rarotonga. But not for EMC or noise fixing jobs with larger
installations.

I'm confused. Are you saying that on most jobs you don't care where the
programmer lives and works? ...


Yes, on most but _not_ all. That's key.

So you could use FPGA instead of an MCU on most of your designs? I'm
still confused. Are you saying if you can't use a part on all of your
designs you don't want to use it on any?


No, what I am saying is the it doesn't matter much which parts I use (my
clients decide that anyhow) but that finding a programmer locally can be
important. Some projects will not really come off the ground if the
programmer isn't local. Or it can take forever.

That is the point I am trying to dispute. My experience has been that a
remote team is a very capable team and can do pretty much any job.
Colocation is seldom an important issue. So far your statements have
all supported that with a few exceptions. At least that is how I have
read the words. "Some projects", "For most work it doesn't
matter where the worker is", etc... YMMV

... I think that is what you said, but it
sounds like you are trying to disagree with me.


I disagree with the statement "it doesn't matter where the worker is".
Because sometimes (not always) it does matter. And when it does, close
proximity is very important. Then you need to literally work
side-by-side. Done it many times.

Our local SW guy sold his horse ranch and moved out of California. Only
to Reno which is under 2h drive but that's already a bit far. And in
winter you might not get through the pass or can't get back home.

I have done many jobs remotely and it has *never* been a problem. If
debugging is needed in the field, that is not the same thing as saying
the developer has to be in the field. You are welcome to disagree on this.


I do disagree.

Ok, but the examples you give tend to support remote work except in a
few cases. I'm just reading the words you wrote, I'm not putting them
in your mouth.

I can only remember one time where I iterated through design changes in
the field and that was actually a case where I could have done it all
remotely, but I was pleasing the customer to be there. Turns out he
wasn't initializing the design right and it was hard to detect.


Well, if you are standing next to a huge roaring engine and this, that
and the other subtle disturbance has to be ironed out it would be a
major problem if the programmer is three time zones away. You don't have
to believe me but that's how it is with some of my assignments.

Just like EMC jobs on large gear can simply not be done remotely. Which
is why I bought the Signalhound analyzer (fits into carry-on).

I don't argue your needs. You keep saying these special jobs are a
small percentage of your work. So most assignments will work just fine
with remote support, no?

One big advantage to FPGAs is the ability to simulate at a low level. it
is very easy to emulate the I/O in an HDL simulation. I don't know how
they do that with MCUs, but in the FPGA world I've never had a problem.


That is undoubtedly true. Plus probably less in errata headaches.

[...]


I've used schematic based tools and both VHDL and Verilog. I've worked
with the vendor's tools and third party tools including the NeoCAD tools
which became Xilinx tools when Xilinx bought them.

If anyone tells you they only know one brand of FPGA you are talking to
an FPGA weenie. I find MCUs to vary a *great* deal more than FPGAs in
terms of usage. MCUs need all sorts of start up code and peripheral
drivers, clock control, etc, etc, etc. FPGAs not so much. They mostly
have the same features and most of that can be inferred from the HDL so
you never need to look too hard under the hood.

In short, there is a lot of FUD about FPGAs. Talk to someone who
doesn't buy into the FUD.


Yeah, maybe next time I need major logic we should talk. But better not
about politics

Yeah... Even if you need minor logic let's talk. I find the real
advantage to FPGAs is in the fact that I can do almost *anything* in
one. I don't need to add stuff unless it is very application specific
like the CD quality CODEC on my current production board. I could get
CD quality from an FPGA design, but it wouldn't be worth the work to
save a $3 part.


So far the next project on the books that will contain logic is 2nd half
of next year. It will need a 16-bit audio codec as well but we can use
an external chip for that, PCM29xx series et cetera. Would (probably)
even keep it external with a uC because the 16-bit ADCs on those aren't
very quiet.

Not sure what the requirements are for your CODEC, but I have been using
the AKM parts with good results. Minimal or *no* programming,
configuration is done by a small number of select pins, very simple. I
have yet to find another one as small, AK4552, AK4556.

Things quickly unravel when you start relying on real hardware that is
on uC but not on FPGA. Comparators, ADCs, analog muxes, for example.

If you really need it all on a single chip, then yes, you won't find
that on so many FPGAs although Microsemi has their Fusion line with
analog. My cash cow uses a single FPGA and a stereo CODEC. That was
smaller than any MCU design because the MCU would still require the
CODEC (CD quality) and some of the control logic and interface could not
be done with any conventional MCU. I had to vary the speed of the CODEC
clock via an ADPLL to synchronize it with an incoming data stream. I
don't know how to do that with an MCU and no logic. But I can do it all
with FPGA logic and no MCU.


Hmm, I was looking at audio interfacing just yesterday because I am
going to need that on one new project. There's plenty out there that
should be directly adressable via MCU. For me it's probably going to be
something from the PCM290x series but there's also SPI variants and so
on.

Anyhow, I am also going to need ADC and comparator, including muxes for
them, so this one will likely be a uC case again because otherwise all
this has to be added externally.

You do know that it is not hard to add an ADC to an FPGA? No need for a
mux if all the inputs can be connected to separate pins. It all depends
on the resolution you need. 8 bits is easy, 16 bits - not so easy.


Mine are never less than 12-bit, often 16-bit.

What about delay time? Is sigma-delta ok?

Last week I reviewed a design with some larger FPGA on there. What I
found fairly disgusting was how much they had to be babied with the
power sequencing. uCs don't have that problem.

If you want to work with the wrong device, then you will find it hard to
work with. There are still single voltage devices on the market. If
this was an old design, most likely it was a Spartan 3 or similar era
device when they (for still unknown reasons) used three, yes, count
them, *three* voltages on the FPGA. The 2.5 volt aux supply was there
solely for the configuration interface which was normally to a 3.3 volt
device! Only from Xilinx...

If this was a new device, then I guess they picked one based on
something other than ease of use, eh? Don't assume all FPGAs are the
same.


Well, this guy is a real expert on high-end FPGA and the project
requires stuff with tons of horsepower.

That's fine, just don't judge all FPGAs by the ones you have seen. If
the only MCU you had worked with were ARM 11s using 3 Watts and running
a cell phone down in 8 hours, would you think the PIC MCUs were the same?


Well, give us all here an example of a FPGA that can fully emulate a
TSM320 and costs $3

There are a number of $3 FPGAs. I can't imagine why you would want to
emulate a DSP in an FPGA. I would rather design a project using an
FPGA. TI likely has a restriction about running their code compiled
with their tools in an FPGA softcore. So what is your project?

You are aware that there are Flash based FPGAs that don't require the
external Flash chip, right?


Same with uCs, since a very long time

You are missing my point.


I guess then I don't see your point. Flash is available on almost
everything nowadays.

I was comparing FPGAs to FPGAs. Many FPGAs require external Flash, some
don't. Just like most DSPs require external flash, most MCUs don't.

--

Rick

 

[rickman]

On 9/7/2013 2:11 PM, Ulf Samuelsson wrote:

rickman skrev 2013-09-06 23:12:
On 9/6/2013 4:33 PM, Joerg wrote:
rickman wrote:
On 8/22/2013 1:51 PM, Joerg wrote:
Tim Williams wrote:
"Joerg"<invalid@invalid.invalid> wrote in message
news:b7l1blFlu93U2@mid.individual.net...
I saw people
using 0.1uF and 0.47uF. The datasheet is silent about stuff like
that,
as usual.
It doesn't really matter.

However, not everyone knows that because they don't say much about
the
innards of the chip. It's my first ATMega case, or maybe the 2nd.

Finally gave up and bit the uC bullet? ;-)


Sometimes you need it. A while ago I even had a switcher design that
would have been totally impossible to do without a uC. But it does
raise
eyebrows if I request timers and port pins and MIPS, probably
because of
my analog background. "YOU want some of the uC resources? What for?"

Sounds to me like you need FPGA resources moreso than an MCU. Are you
using the ADC or DAC, guess so or are you using the reference for the
brownout or something else? DACs are easy in FPGAs, ADCs not as easy.
Otherwise FPGAs do everything an MCU does plus...


I nearly always need ADC capability. Not for the brownout, I never trust
anything on those chips for that, the POR/BOR/WDT goes external. FPGA
have some downsides, they tend to become large, expensive and sometimes
power-hungry when you need math capability or an MCU core.

If your FPGA designs are expensive or power hungry, then you are doing
things you can't do in an MCU or you are not using FPGAs properly. They
don't need to use any more power than an MCU and in many cases less.
They certainly don't need to be significantly more expensive unless you
consider every dollar in your designs. At the very low end MCUs can be
under $1 and still have reasonable performance. For $1 you can't get
much in the way of programmable logic. For $3 however, you can get a
chip large enough for a CPU (with math) and room for your special logic.


But the main
issue for many projects is people. If the client has the experts in
house like in this case, fine. But if not then one is better off using a
uC where one can find a programmer in nearly every town. This is one
reason I am often partial to the 8051.

Do you work in *every* town? I find if I need a skill, it doesn't
matter where the worker is. I also find FPGA design is pretty common
these days. If you are ever short on FPGA design skills, give me a shout.


Of course the beauty of FPGA is that the availability of very fast glue
logic. Most uC are sorely lacking in that domain.

Yes, the ideal chip would add a section of FPGA fabric to a conventional
MCU and vary the size just as they do the RAM and Flash. I think at
this point the problem is cultural. Most FPGA companies are all about
the big iron selling for $100 a chip min and the MCU makers don't
understand programmable logic. Xilinx and Cypress is good examples.
Zync is a very high end solution, great if it matches your problem. PSOC
is not a bad idea, but their idea of programmable logic isn't worth much.

Give me a good $10 MCU/FPGA combo and I'll design the world! In the
meantime I'll be using soft cores. They are a lot easier to program
than an MCU anyway.


That was available with the FPSLIC. AVR core with 5/10/40k gates.
Unfortunately the combination of features didn't make sense.

40 MHz AVR with only 36 kB SRAM.

It would have been much better with an ARM7 core
with an external memory bus.

I don't know about the external memory bus, but the problem I had with
the FPSLIC is that I was never convinced it would last. It did however
even with a very limited market penetration. I don't know how large the
FPGA fabric was, nobody usefully measures FPGAs in gates anymore. So
I'm guessing it was actually very limited. I know for a fact it was
rather pricey.

Since it was implemented in a technology, and not shrinked,
it eventually become cheaper to use a softcore with
a standard FPGA in a fine geometry technology.

I came to the conclusion that an MCU company cannot compete with an FPGA
company unless the programmable logic part is only a small percentage of
the die.

Compete how? The FPGA companies are leaving huge segments of the market
open to anyone who has the guts to exploit it.

> It would make sense to have a 5 kgate FPGAs in a modern micro.

I think 5 kgate is a tiny FPGA - what a couple of 22V10s? It would be
about the size of a UART in an MCU design. Try 2-5 kLUTs then you have
a useful device. Otherwise you are just pissing in the wind. The FPGA
fabric should be roughly the same die size as the Flash or RAM and
should scale as the memory does.

The Xilinx Zync and Altera SoC are nice tries, except that most
of the standard peripherals suck and it is still beyond the price
most customers I've seen are prepared to pay.

You need to understand their markets. Their designs are very good for
their markets which are high profit margin. Thinking like a $1 MCU
maker wont let you compete in their space. But you can compete in a $2
to $10 MCU+FPGA space. So get out there and explain it to your
management! Otherwise you lose design wins to softcores which get
cheaper every day.

--

Rick

 

[Joerg]

rickman wrote:

On 9/7/2013 1:59 PM, Joerg wrote:
rickman wrote:
On 9/7/2013 11:10 AM, Joerg wrote:
rickman wrote:
On 9/6/2013 7:10 PM, Joerg wrote:

That is often the problem. Sometimes a buck fifty is the pain
threshold.
Not in this ATMega case, the 2560 is very expensive but comes with
lots
of ADC and analog muxes and all that. Things that will cost extra
with a
FPGA solution and eat real estate.


For $3 however, you can get a
chip large enough for a CPU (with math) and room for your special
logic.


For $3 I can get a big DSP.

What "big" DSP can you get for $3? ...


For example, this:

http://www.ti.com/lit/ds/symlink/tms320c5535.pdf

I don't see it for $3. Did you get a quote for your project? TI says
it is $5 to $8 at qty 1k depending on the flavor. You still need to add
Flash.


1k qty is $3.67 at Digikey:

http://www.digikey.com/product-detail/en/TMS320C5532AZHH10/296-32741-ND/2749713


Not the same part pal. You're trying to pull a fast one on me? Are we
talking about the TMS320C5535 with "tons" of memory or the TMS320C5532
with *much* less memory?

It doesn't have the single access RAM but it does have 64k dual access
RAM. That's a lot of RAM in embedded.

$3.02 with 12wks leadtime at Arrow:

http://components.arrow.com/part/detail/51425505S8988412N7713?region=na

ROM is included.

ROM is not Flash.. is it? Are you thinking in terms of a mask ROM?

You can use the bootloader or OTP your own bootloader if you don't want
to store your programming in ROM. In most situations this is part of a
larger computerized system from where it can download its programming.

... It has been a while since I looked
hard at DSP chips, but I don't recall any I would call remotely "big"
for $3. The TI chips that would be "big" are the TMS6xxx line which
start somewhere around $20 the last time I looked and that requires
all
memory and I/O to be separate. The smaller DSP chips that you can get
for the $3 range are not "big" in any sense and only a very few of
them
include Flash memory. So you still need another chip.


It has tons of memory on board.

Yes, and many FPGAs have "tons" of memory on board although not for
$3... but then this isn't a $3 part either...


It is a $3 part. See above.

No, you need to pick a part number and stick with it.

I gave a part number. Still waiting for your $3 FPGA part number

Even a "small" FPGA can run rings around a DSP when it comes to
performance. Usually "big" in DSPs means fast and when you want
really
fast DSP you use an FPGA with all the parallelism you can handle.
DSPs
can't touch FPGAs for speed, even with low power.


Most of the really powerful FPGA that I connected to or had to review
designs with them in there were painfully expensive.

Because you were looking at FPGAs that were "painfully" large I'm sure.
How many pins, 256, 400+...? 20,000 LUTs, 40,000 LUTs?


Sure, that's why I wrote "powerful". The less powerful ones have never
impressed me much but I have to admit that I haven't looked the last
five years. So, tell us, which FPGA can fully replace the above DSP for
three bucks and where could one buy it off the shelf?

Lol, I don't know where you are coming from now. You don't like the
large FPGAs because they use power like they are... well, large. You
don't like the small FPGAs because they are, well... small.

When you stop using terms like "powerful" and want to actually consider
an FPGA for a design I can help you. Gut feel is nice as long as it is
based in fact.

So then, what would be an FPGA that can fully contain the above TMS320
and what does it cost?

Which one could replace the MSP430F6733 including its ADCs and all, for
around $3?

http://www.ti.com/lit/ds/symlink/msp430f6720.pdf

[...]

I can only remember one time where I iterated through design changes in
the field and that was actually a case where I could have done it all
remotely, but I was pleasing the customer to be there. Turns out he
wasn't initializing the design right and it was hard to detect.


Well, if you are standing next to a huge roaring engine and this, that
and the other subtle disturbance has to be ironed out it would be a
major problem if the programmer is three time zones away. You don't have
to believe me but that's how it is with some of my assignments.

Just like EMC jobs on large gear can simply not be done remotely. Which
is why I bought the Signalhound analyzer (fits into carry-on).

I don't argue your needs. You keep saying these special jobs are a
small percentage of your work. So most assignments will work just fine
with remote support, no?

Yes, for myself I'd say it's >90%. For firmware and software support,
much lower percentage. Currently <50% of cases. Meaning I (or some other
folks) and the programmers have to literally work side-by-side.

Mostly this simply has to do with the fact that gear is too large to
ship and often also because operation by someone not used to it can
become dangerous. When pressures are several thousand psi and someone
screws up people could die.

One big advantage to FPGAs is the ability to simulate at a low level. it
is very easy to emulate the I/O in an HDL simulation. I don't know how
they do that with MCUs, but in the FPGA world I've never had a problem.


That is undoubtedly true. Plus probably less in errata headaches.

[...]


I've used schematic based tools and both VHDL and Verilog. I've
worked
with the vendor's tools and third party tools including the NeoCAD
tools
which became Xilinx tools when Xilinx bought them.

If anyone tells you they only know one brand of FPGA you are
talking to
an FPGA weenie. I find MCUs to vary a *great* deal more than FPGAs in
terms of usage. MCUs need all sorts of start up code and peripheral
drivers, clock control, etc, etc, etc. FPGAs not so much. They
mostly
have the same features and most of that can be inferred from the
HDL so
you never need to look too hard under the hood.

In short, there is a lot of FUD about FPGAs. Talk to someone who
doesn't buy into the FUD.


Yeah, maybe next time I need major logic we should talk. But better not
about politics

Yeah... Even if you need minor logic let's talk. I find the real
advantage to FPGAs is in the fact that I can do almost *anything* in
one. I don't need to add stuff unless it is very application specific
like the CD quality CODEC on my current production board. I could get
CD quality from an FPGA design, but it wouldn't be worth the work to
save a $3 part.


So far the next project on the books that will contain logic is 2nd half
of next year. It will need a 16-bit audio codec as well but we can use
an external chip for that, PCM29xx series et cetera. Would (probably)
even keep it external with a uC because the 16-bit ADCs on those aren't
very quiet.

Not sure what the requirements are for your CODEC, but I have been using
the AKM parts with good results. Minimal or *no* programming,
configuration is done by a small number of select pins, very simple. I
have yet to find another one as small, AK4552, AK4556.

Plus their prices are quite good.

[...]

You do know that it is not hard to add an ADC to an FPGA? No need for a
mux if all the inputs can be connected to separate pins. It all depends
on the resolution you need. 8 bits is easy, 16 bits - not so easy.


Mine are never less than 12-bit, often 16-bit.

What about delay time? Is sigma-delta ok?

As long as I can get into the tens of ksps.

Last week I reviewed a design with some larger FPGA on there. What I
found fairly disgusting was how much they had to be babied with the
power sequencing. uCs don't have that problem.

If you want to work with the wrong device, then you will find it
hard to
work with. There are still single voltage devices on the market. If
this was an old design, most likely it was a Spartan 3 or similar era
device when they (for still unknown reasons) used three, yes, count
them, *three* voltages on the FPGA. The 2.5 volt aux supply was there
solely for the configuration interface which was normally to a 3.3
volt
device! Only from Xilinx...

If this was a new device, then I guess they picked one based on
something other than ease of use, eh? Don't assume all FPGAs are the
same.


Well, this guy is a real expert on high-end FPGA and the project
requires stuff with tons of horsepower.

That's fine, just don't judge all FPGAs by the ones you have seen. If
the only MCU you had worked with were ARM 11s using 3 Watts and running
a cell phone down in 8 hours, would you think the PIC MCUs were the
same?


Well, give us all here an example of a FPGA that can fully emulate a
TSM320 and costs $3

There are a number of $3 FPGAs. I can't imagine why you would want to
emulate a DSP in an FPGA. I would rather design a project using an
FPGA. TI likely has a restriction about running their code compiled
with their tools in an FPGA softcore. So what is your project?

I wasn't referring to a specific project, just your claim that FPGA can
do the same job as processors at the same price.

One project will probably require something of the caliber of a
MSP430F6733. Whether this kind or a DSP, what is key is that we are able
to use pre-coooked library routines. In my case for complex (I/Q) signal
processing, FFT, non-linear filtering and so on. Sometimes legacy
routines must be kept and in an FPGA that would require an IP block that
can emulate the respective processor well enough.

But what I see most is this: The respective client has in-house talent
for writing code. They are familiar with a particular architecture, have
a vast arsenal of re-usable code built up, and naturally they do not
wish to give this up. If it's a dsPIC like last year, then that goes in
there. If it's Atmel and MSP430 like this year, then that is used. Has
to be, the customer is king.

[...]

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

rickman wrote:

On 9/7/2013 12:32 PM, Joerg wrote:
rickman wrote:

You can get the 1 kLUT parts for under $3 and possibly the 4 kLUT parts.
It has been a while since I got a quote. The 1 kLUT part is big
enough
for a soft core MCU plus some custom logic.



Got a mfg and part number? Or a Digikey link?

At Digikey search on iCE40. That will give you a listing of all the
parts. Looks like Digikey's prices are a little high, not just because
they are Digikey. The $3 figure I gave is from quotes I got from
Silicon Blue before they were traded through Digikey. ...

Which part number?

I don't see how the equivalent of a TMS320 or a big MSP430 could fit
into one of these small Lattice devices.

... Like I said, you
need to get a quote on any FPGA to find the "real" price.

I don't play those games. Or only once every 20-some years when buying a
car, and then the car dealer may develop an ulcer when we are done.

BTW, with MCUs Digikey will give you a realistic price quote. In the
FPGA world the distis never give you a good price unless you ask for a
quantity quote. I have gotten prices quoted to me that were half the
list price. FPGA companies play a different marketing game and have a
lot of room to negotiate in order to buy a socket.


Yeah, the old haggle game. Beats my why they still cling to such
medieval sales tactics. The only other market where that is customary is
with used car salesmen.

They don't even know how much in business opportunity they are missing
because of this. Guys like me need pricing info here, this minute, right
now. If there is even as much as a label "Call" I usually move on.

I don't think it is all about the "haggle". I think no small part is
about doing what it takes to get the design in and deny the competition.
When you get quotes from Digikey web site they never even know you are
looking at their parts. Think of it as a live auction vs. sealed bids.
They prefer to be in the live auction.

Well, most design engineers don't. tti lost a deal on capacitors last
week because they wouldn't let me look at the details of a cap without
entering some stupid captcha. Which as usual didn't work. I moved on and
found it elsewhere. I simply do not have the time for such games.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

Ulf Samuelsson wrote:

[...]

I came to the conclusion that an MCU company cannot compete with an FPGA
company unless the programmable logic part is only a small percentage of
the die.

They can compete, with the peripherals. But those have to be of good
performance and most of all versatile enough. Some things can probably
be achieved in simple ways. For example, by providing the option to map
two pins per ADC channel for folks who need it to be low noise.

It would make sense to have a 5 kgate FPGAs in a modern micro.

Bingo! That would be fantastic.

The Xilinx Zync and Altera SoC are nice tries, except that most
of the standard peripherals suck and it is still beyond the price
most customers I've seen are prepared to pay.

I hope this doesn't rub you the wrong way but Atmel often ain't that
great either when it comes to peripherals. When I looked at the
"reference" in the ATMega2560 that we just designed in I almost got
sick. In the relayout we piped in our own reference.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Paul Rubin]

Joerg <invalid@invalid.invalid> writes:

I don't see how the equivalent of a TMS320 or a big MSP430 could fit
into one of these small Lattice devices.

I had thought the parts of those processors that would bloat up badly
(instruction decode etc.) are pretty simple so the overall effect of the
bloat is ok in the scheme of things. The parts doing the most work
(memory, arithmetic) are done in the FPGA hardware (RAM and DSP blocks,
adders connected to the LUT's somehow) as efficiently as on the MCU's.

I do think softcores seem like a silly idea a lot of the time, and am
looking forward to more low end FPGA's with MCU blocks.

 

[rickman]

On 9/7/2013 3:39 PM, Joerg wrote:

rickman wrote:
On 9/7/2013 1:59 PM, Joerg wrote:
rickman wrote:
On 9/7/2013 11:10 AM, Joerg wrote:
rickman wrote:
On 9/6/2013 7:10 PM, Joerg wrote:

That is often the problem. Sometimes a buck fifty is the pain
threshold.
Not in this ATMega case, the 2560 is very expensive but comes with
lots
of ADC and analog muxes and all that. Things that will cost extra
with a
FPGA solution and eat real estate.


For $3 however, you can get a
chip large enough for a CPU (with math) and room for your special
logic.


For $3 I can get a big DSP.

What "big" DSP can you get for $3? ...


For example, this:

http://www.ti.com/lit/ds/symlink/tms320c5535.pdf

I don't see it for $3. Did you get a quote for your project? TI says
it is $5 to $8 at qty 1k depending on the flavor. You still need to add
Flash.


1k qty is $3.67 at Digikey:

http://www.digikey.com/product-detail/en/TMS320C5532AZHH10/296-32741-ND/2749713


Not the same part pal. You're trying to pull a fast one on me? Are we
talking about the TMS320C5535 with "tons" of memory or the TMS320C5532
with *much* less memory?


It doesn't have the single access RAM but it does have 64k dual access
RAM. That's a lot of RAM in embedded.

You do this often. Start talking about one thing and shift the context
to another. Projects have design requirements. I often am able to meet
my design requirements with an FPGA and no MCU. I often can't say the
opposite, being able to use an MCU without the FPGA.

$3.02 with 12wks leadtime at Arrow:

http://components.arrow.com/part/detail/51425505S8988412N7713?region=na

ROM is included.

ROM is not Flash.. is it? Are you thinking in terms of a mask ROM?


You can use the bootloader or OTP your own bootloader if you don't want
to store your programming in ROM. In most situations this is part of a
larger computerized system from where it can download its programming.

That's a different wrinkle. It is common to have a micro load an FPGA,
many don't contain their own Flash. But I haven't seen this done with
DSPs as often and almost never with MCUs. But if that works for your
project, great. You certainly wouldn't have a problem loading an FPGA
then.

... It has been a while since I looked
hard at DSP chips, but I don't recall any I would call remotely "big"
for $3. The TI chips that would be "big" are the TMS6xxx line which
start somewhere around $20 the last time I looked and that requires
all
memory and I/O to be separate. The smaller DSP chips that you can get
for the $3 range are not "big" in any sense and only a very few of
them
include Flash memory. So you still need another chip.


It has tons of memory on board.

Yes, and many FPGAs have "tons" of memory on board although not for
$3... but then this isn't a $3 part either...


It is a $3 part. See above.

No, you need to pick a part number and stick with it.


I gave a part number. Still waiting for your $3 FPGA part number

Actually you gave me two part numbers, one for $5 and one for just over
$3. What's your point? I gave you info to find the iCE40 line. Xilinx
also makes FPGAs that are very affordable and does Altera and Lattice.

Even a "small" FPGA can run rings around a DSP when it comes to
performance. Usually "big" in DSPs means fast and when you want
really
fast DSP you use an FPGA with all the parallelism you can handle.
DSPs
can't touch FPGAs for speed, even with low power.


Most of the really powerful FPGA that I connected to or had to review
designs with them in there were painfully expensive.

Because you were looking at FPGAs that were "painfully" large I'm sure.
How many pins, 256, 400+...? 20,000 LUTs, 40,000 LUTs?


Sure, that's why I wrote "powerful". The less powerful ones have never
impressed me much but I have to admit that I haven't looked the last
five years. So, tell us, which FPGA can fully replace the above DSP for
three bucks and where could one buy it off the shelf?

Lol, I don't know where you are coming from now. You don't like the
large FPGAs because they use power like they are... well, large. You
don't like the small FPGAs because they are, well... small.

When you stop using terms like "powerful" and want to actually consider
an FPGA for a design I can help you. Gut feel is nice as long as it is
based in fact.


So then, what would be an FPGA that can fully contain the above TMS320
and what does it cost?

Which one could replace the MSP430F6733 including its ADCs and all, for
around $3?

http://www.ti.com/lit/ds/symlink/msp430f6720.pdf

I have already explained that I would never do a design in an FPGA to
wholly incorporate a DSP or MCU. That would be absurd. So why do you
keep asking about that?

Depending on your design requirements there are any number of FPGAs that
will do the job and some may be $3. What are your design requirements?

I can only remember one time where I iterated through design changes in
the field and that was actually a case where I could have done it all
remotely, but I was pleasing the customer to be there. Turns out he
wasn't initializing the design right and it was hard to detect.


Well, if you are standing next to a huge roaring engine and this, that
and the other subtle disturbance has to be ironed out it would be a
major problem if the programmer is three time zones away. You don't have
to believe me but that's how it is with some of my assignments.

Just like EMC jobs on large gear can simply not be done remotely. Which
is why I bought the Signalhound analyzer (fits into carry-on).

I don't argue your needs. You keep saying these special jobs are a
small percentage of your work. So most assignments will work just fine
with remote support, no?


Yes, for myself I'd say it's>90%. For firmware and software support,
much lower percentage. Currently<50% of cases. Meaning I (or some other
folks) and the programmers have to literally work side-by-side.

Mostly this simply has to do with the fact that gear is too large to
ship and often also because operation by someone not used to it can
become dangerous. When pressures are several thousand psi and someone
screws up people could die.

I understand the concept of work that can't be moved. You don't need to
continue to explain that. I was asking why you said most of your word
didn't have that requirement and yet you still were debating the point.
Now I get it, you are talking about two different things, work that
can be moved and work that can't be moved.

One big advantage to FPGAs is the ability to simulate at a low level. it
is very easy to emulate the I/O in an HDL simulation. I don't know how
they do that with MCUs, but in the FPGA world I've never had a problem.


That is undoubtedly true. Plus probably less in errata headaches.

[...]


I've used schematic based tools and both VHDL and Verilog. I've
worked
with the vendor's tools and third party tools including the NeoCAD
tools
which became Xilinx tools when Xilinx bought them.

If anyone tells you they only know one brand of FPGA you are
talking to
an FPGA weenie. I find MCUs to vary a *great* deal more than FPGAs in
terms of usage. MCUs need all sorts of start up code and peripheral
drivers, clock control, etc, etc, etc. FPGAs not so much. They
mostly
have the same features and most of that can be inferred from the
HDL so
you never need to look too hard under the hood.

In short, there is a lot of FUD about FPGAs. Talk to someone who
doesn't buy into the FUD.


Yeah, maybe next time I need major logic we should talk. But better not
about politics

Yeah... Even if you need minor logic let's talk. I find the real
advantage to FPGAs is in the fact that I can do almost *anything* in
one. I don't need to add stuff unless it is very application specific
like the CD quality CODEC on my current production board. I could get
CD quality from an FPGA design, but it wouldn't be worth the work to
save a $3 part.


So far the next project on the books that will contain logic is 2nd half
of next year. It will need a 16-bit audio codec as well but we can use
an external chip for that, PCM29xx series et cetera. Would (probably)
even keep it external with a uC because the 16-bit ADCs on those aren't
very quiet.

Not sure what the requirements are for your CODEC, but I have been using
the AKM parts with good results. Minimal or *no* programming,
configuration is done by a small number of select pins, very simple. I
have yet to find another one as small, AK4552, AK4556.


Plus their prices are quite good.

Which, AKM or the other? I'd like to think I can get a CD quality CODEC
for $3 from nearly anyone. I mainly picked AKM because of the size, 6x6
mm without going to a microBGA.

You do know that it is not hard to add an ADC to an FPGA? No need for a
mux if all the inputs can be connected to separate pins. It all depends
on the resolution you need. 8 bits is easy, 16 bits - not so easy.


Mine are never less than 12-bit, often 16-bit.

What about delay time? Is sigma-delta ok?


As long as I can get into the tens of ksps.

High 10's or low 10's. Up to say, 20 or 30 ksps is easy to do in an
FPGA with decent resolution, 12 bits. Getting 16 bits is harder, I've
not tried it, but should be possible.

I was looking at using a LVDS input for a comparator and Xilinx did it
in a demo of a SDR. They are very short on details, but they talk about
1 mV on the input. I know that's not anything special, I'm hoping to do
better, much better.

Last week I reviewed a design with some larger FPGA on there. What I
found fairly disgusting was how much they had to be babied with the
power sequencing. uCs don't have that problem.

If you want to work with the wrong device, then you will find it
hard to
work with. There are still single voltage devices on the market. If
this was an old design, most likely it was a Spartan 3 or similar era
device when they (for still unknown reasons) used three, yes, count
them, *three* voltages on the FPGA. The 2.5 volt aux supply was there
solely for the configuration interface which was normally to a 3.3
volt
device! Only from Xilinx...

If this was a new device, then I guess they picked one based on
something other than ease of use, eh? Don't assume all FPGAs are the
same.


Well, this guy is a real expert on high-end FPGA and the project
requires stuff with tons of horsepower.

That's fine, just don't judge all FPGAs by the ones you have seen. If
the only MCU you had worked with were ARM 11s using 3 Watts and running
a cell phone down in 8 hours, would you think the PIC MCUs were the
same?


Well, give us all here an example of a FPGA that can fully emulate a
TSM320 and costs $3

There are a number of $3 FPGAs. I can't imagine why you would want to
emulate a DSP in an FPGA. I would rather design a project using an
FPGA. TI likely has a restriction about running their code compiled
with their tools in an FPGA softcore. So what is your project?


I wasn't referring to a specific project, just your claim that FPGA can
do the same job as processors at the same price.

Yes, that is my claim. The obvious exception is when some feature is
needed that just isn't available in an FPGA. I'm not saying *every*
project can be done better in an FPGA. I'm saying that designers tend
to just not consider FPGAs when they are often viable solutions.

One project will probably require something of the caliber of a
MSP430F6733. Whether this kind or a DSP, what is key is that we are able
to use pre-coooked library routines. In my case for complex (I/Q) signal
processing, FFT, non-linear filtering and so on. Sometimes legacy
routines must be kept and in an FPGA that would require an IP block that
can emulate the respective processor well enough.

Ok, that is likely a no-go. If you really want to emulate a DSP chip
then an FPGA is not likely to be a useful way to proceed. Wanting to
run DSP precompiled library code is a bit of an extreme requirement. If
the customer wants a DSP, then by all means give them a DSP. But don't
automatically exclude an FPGA from the task.

But what I see most is this: The respective client has in-house talent
for writing code. They are familiar with a particular architecture, have
a vast arsenal of re-usable code built up, and naturally they do not
wish to give this up. If it's a dsPIC like last year, then that goes in
there. If it's Atmel and MSP430 like this year, then that is used. Has
to be, the customer is king.

Yeah, well that is a deal killer for *any* other alternative. That is
not related to what I was saying. My point is that if you don't have
any specific requirement that dictates the use of a given chip, an FPGA
has as good a chance at meeting the requirements as an MCU or DSP. In
fact, FPGAs are what get used when DSPs aren't fast enough. My point is
you don't have to limit them to the high end. They also do very well at
the low end.

--

Rick

 

[Joerg]

Paul Rubin wrote:

Joerg <invalid@invalid.invalid> writes:
I don't see how the equivalent of a TMS320 or a big MSP430 could fit
into one of these small Lattice devices.

I had thought the parts of those processors that would bloat up badly
(instruction decode etc.) are pretty simple so the overall effect of the
bloat is ok in the scheme of things. The parts doing the most work
(memory, arithmetic) are done in the FPGA hardware (RAM and DSP blocks,
adders connected to the LUT's somehow) as efficiently as on the MCU's.

I do think softcores seem like a silly idea a lot of the time, and am
looking forward to more low end FPGA's with MCU blocks.

Much of it has to do with legacy code. Yes, some things could even be
done more efficiently in the FPGA because you can actually streamline
the HW to the task, something neither uC nor DSP allow. For example, why
have a 32-bit HW multiplier when you know you'll never exceed 23 bits?
But legacy code won't run anymore and you need FPGA specialists to make
it all work.

It's like with Excel. There's better programs out there but one core
reason why companies stick to it is the huge repository of VBA
applications they have created over the years.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[rickman]

On 9/7/2013 4:33 PM, Paul Rubin wrote:

Joerg<invalid@invalid.invalid> writes:
I don't see how the equivalent of a TMS320 or a big MSP430 could fit
into one of these small Lattice devices.

I had thought the parts of those processors that would bloat up badly
(instruction decode etc.) are pretty simple so the overall effect of the
bloat is ok in the scheme of things. The parts doing the most work
(memory, arithmetic) are done in the FPGA hardware (RAM and DSP blocks,
adders connected to the LUT's somehow) as efficiently as on the MCU's.

I do think softcores seem like a silly idea a lot of the time, and am
looking forward to more low end FPGA's with MCU blocks.

How about an MCU array instead?

http://www.greenarraychips.com/

BTW, considering a softcore "silly" is not a useful engineering
analysis. Softcores can save money and/or time in a project. But then
people often have biases and aren't willing to look at things from a
different perspective.

Bernd Paysan rolled his own small processor design for an ASIC and was
able to save time *and* money in development as well as silicon cost
over using a canned core in a custom ASIC design. Dig around a bit and
find the B16 for more details. Or he would be happy to relate the
fiasco of the whole project (it started with an 8051 core).

--

Rick

 

[rickman]

On 9/7/2013 4:46 PM, Joerg wrote:

Paul Rubin wrote:
Joerg<invalid@invalid.invalid> writes:
I don't see how the equivalent of a TMS320 or a big MSP430 could fit
into one of these small Lattice devices.

I had thought the parts of those processors that would bloat up badly
(instruction decode etc.) are pretty simple so the overall effect of the
bloat is ok in the scheme of things. The parts doing the most work
(memory, arithmetic) are done in the FPGA hardware (RAM and DSP blocks,
adders connected to the LUT's somehow) as efficiently as on the MCU's.

I do think softcores seem like a silly idea a lot of the time, and am
looking forward to more low end FPGA's with MCU blocks.


Much of it has to do with legacy code. Yes, some things could even be
done more efficiently in the FPGA because you can actually streamline
the HW to the task, something neither uC nor DSP allow. For example, why
have a 32-bit HW multiplier when you know you'll never exceed 23 bits?
But legacy code won't run anymore and you need FPGA specialists to make
it all work.

No, you would need a DSP specialist. The FPGA designer only needs to
know how to code the FPGA.

But that is exactly the point of the FPGA in DSP apps. You code to the
app, not to a processor.

--

Rick

 

[Paul Rubin]

rickman <gnuarm@gmail.com> writes:
> How about an MCU array instead? http://www.greenarraychips.com/

Yes, we've had many discussions about that part ;-).

> considering a softcore "silly" is not a useful engineering analysis.

The engineering analysis is implied: it takes far more silicon to
implement a microprocessor in LUTs than directly in silicon, plus you
lose a lot of speed because of all the additional layers and lookups.

> Bernd Paysan rolled his own small processor design for an ASIC

Yes, the ASIC bypassed the relative inefficiency of doing the same thing
in FPGA's. It would be cool to have some tiny processors like that
available as hard cells on small FPGA's.

 

[Joerg]

rickman wrote:

On 9/7/2013 3:39 PM, Joerg wrote:
rickman wrote:
On 9/7/2013 1:59 PM, Joerg wrote:
rickman wrote:
On 9/7/2013 11:10 AM, Joerg wrote:
rickman wrote:
On 9/6/2013 7:10 PM, Joerg wrote:

That is often the problem. Sometimes a buck fifty is the pain
threshold.
Not in this ATMega case, the 2560 is very expensive but comes with
lots
of ADC and analog muxes and all that. Things that will cost extra
with a
FPGA solution and eat real estate.


For $3 however, you can get a
chip large enough for a CPU (with math) and room for your special
logic.


For $3 I can get a big DSP.

What "big" DSP can you get for $3? ...


For example, this:

http://www.ti.com/lit/ds/symlink/tms320c5535.pdf

I don't see it for $3. Did you get a quote for your project? TI says
it is $5 to $8 at qty 1k depending on the flavor. You still need
to add
Flash.


1k qty is $3.67 at Digikey:

http://www.digikey.com/product-detail/en/TMS320C5532AZHH10/296-32741-ND/2749713



Not the same part pal. You're trying to pull a fast one on me? Are we
talking about the TMS320C5535 with "tons" of memory or the TMS320C5532
with *much* less memory?


It doesn't have the single access RAM but it does have 64k dual access
RAM. That's a lot of RAM in embedded.

You do this often. Start talking about one thing and shift the context
to another. ...

I didn't. I said it is a DSP with large memory, which it is.

... Projects have design requirements. I often am able to meet
my design requirements with an FPGA and no MCU. I often can't say the
opposite, being able to use an MCU without the FPGA.


$3.02 with 12wks leadtime at Arrow:

http://components.arrow.com/part/detail/51425505S8988412N7713?region=na

ROM is included.

ROM is not Flash.. is it? Are you thinking in terms of a mask ROM?


You can use the bootloader or OTP your own bootloader if you don't want
to store your programming in ROM. In most situations this is part of a
larger computerized system from where it can download its programming.

That's a different wrinkle. It is common to have a micro load an FPGA,
many don't contain their own Flash. But I haven't seen this done with
DSPs as often and almost never with MCUs. But if that works for your
project, great. You certainly wouldn't have a problem loading an FPGA
then.

The fact that most FPGA don't have flash is fine ... but ... there must
be a decent bootloader inside. In one of the upcoming projects it must
be able to bootload via USB. So the device must wake up with a certain
minimum in brain functionality to handle the USB stuff. With FPGA that
can become a challenge unless you provide a serial memory device (which
adds cost).

... It has been a while since I looked
hard at DSP chips, but I don't recall any I would call remotely
"big"
for $3. The TI chips that would be "big" are the TMS6xxx line which
start somewhere around $20 the last time I looked and that requires
all
memory and I/O to be separate. The smaller DSP chips that you
can get
for the $3 range are not "big" in any sense and only a very few of
them
include Flash memory. So you still need another chip.


It has tons of memory on board.

Yes, and many FPGAs have "tons" of memory on board although not for
$3... but then this isn't a $3 part either...


It is a $3 part. See above.

No, you need to pick a part number and stick with it.


I gave a part number. Still waiting for your $3 FPGA part number

Actually you gave me two part numbers, one for $5 and one for just over
$3. What's your point? I gave you info to find the iCE40 line. Xilinx
also makes FPGAs that are very affordable and does Altera and Lattice.

Both of the ones I gave you are $3. The DSP costs $3.02 and the MSP430
is $3.09. These are over-the-counter no-haggle prices. Can a $3 iCE40
device emulate a TMS320 or a big MSP430? I can't tell because I don't
know this Lattice series and I am not an FPGA expert. But it sure looks
like they'd have a hard time.

Even a "small" FPGA can run rings around a DSP when it comes to
performance. Usually "big" in DSPs means fast and when you want
really
fast DSP you use an FPGA with all the parallelism you can handle.
DSPs
can't touch FPGAs for speed, even with low power.


Most of the really powerful FPGA that I connected to or had to review
designs with them in there were painfully expensive.

Because you were looking at FPGAs that were "painfully" large I'm
sure.
How many pins, 256, 400+...? 20,000 LUTs, 40,000 LUTs?


Sure, that's why I wrote "powerful". The less powerful ones have never
impressed me much but I have to admit that I haven't looked the last
five years. So, tell us, which FPGA can fully replace the above DSP for
three bucks and where could one buy it off the shelf?

Lol, I don't know where you are coming from now. You don't like the
large FPGAs because they use power like they are... well, large. You
don't like the small FPGAs because they are, well... small.

When you stop using terms like "powerful" and want to actually consider
an FPGA for a design I can help you. Gut feel is nice as long as it is
based in fact.


So then, what would be an FPGA that can fully contain the above TMS320
and what does it cost?

Which one could replace the MSP430F6733 including its ADCs and all, for
around $3?

http://www.ti.com/lit/ds/symlink/msp430f6720.pdf

I have already explained that I would never do a design in an FPGA to
wholly incorporate a DSP or MCU. That would be absurd. So why do you
keep asking about that?

Because you wrote yesterday, quote "For $3 however, you can get a chip
large enough for a CPU (with math) and room for your special logic".

Depending on your design requirements there are any number of FPGAs that
will do the job and some may be $3. What are your design requirements?

As I said, I do not have any hammered out ones yet but it'll come. This
was just about you $3 claim. So I gave some examples of devices that
cost $3.

I can only remember one time where I iterated through design
changes in
the field and that was actually a case where I could have done it all
remotely, but I was pleasing the customer to be there. Turns out he
wasn't initializing the design right and it was hard to detect.


Well, if you are standing next to a huge roaring engine and this, that
and the other subtle disturbance has to be ironed out it would be a
major problem if the programmer is three time zones away. You don't
have
to believe me but that's how it is with some of my assignments.

Just like EMC jobs on large gear can simply not be done remotely. Which
is why I bought the Signalhound analyzer (fits into carry-on).

I don't argue your needs. You keep saying these special jobs are a
small percentage of your work. So most assignments will work just fine
with remote support, no?


Yes, for myself I'd say it's>90%. For firmware and software support,
much lower percentage. Currently<50% of cases. Meaning I (or some other
folks) and the programmers have to literally work side-by-side.

Mostly this simply has to do with the fact that gear is too large to
ship and often also because operation by someone not used to it can
become dangerous. When pressures are several thousand psi and someone
screws up people could die.

I understand the concept of work that can't be moved. You don't need to
continue to explain that. I was asking why you said most of your word
didn't have that requirement and yet you still were debating the point.
Now I get it, you are talking about two different things, work that can
be moved and work that can't be moved.

Yup. Hence the need for availability of local programmer talent. Less
local availability means potential problems. That is because (where
possible) I like to use architectures I am familiar with.

Programmer talent means longterm. For example, if a client has an issue
with an 8051 design long after the original programmer has moved on I
could find programmers within a 10-mile radius. Try that with an FPGA.
In San Jose it may be possible but not out here.

[...]

Not sure what the requirements are for your CODEC, but I have been using
the AKM parts with good results. Minimal or *no* programming,
configuration is done by a small number of select pins, very simple. I
have yet to find another one as small, AK4552, AK4556.


Plus their prices are quite good.

Which, AKM or the other? I'd like to think I can get a CD quality CODEC
for $3 from nearly anyone. I mainly picked AKM because of the size, 6x6
mm without going to a microBGA.

AKM has good prices.

You do know that it is not hard to add an ADC to an FPGA? No need
for a
mux if all the inputs can be connected to separate pins. It all
depends
on the resolution you need. 8 bits is easy, 16 bits - not so easy.


Mine are never less than 12-bit, often 16-bit.

What about delay time? Is sigma-delta ok?


As long as I can get into the tens of ksps.

High 10's or low 10's. Up to say, 20 or 30 ksps is easy to do in an
FPGA with decent resolution, 12 bits. Getting 16 bits is harder, I've
not tried it, but should be possible.

Mostly I need 40-50ksps. But 20 is often ok.

I was looking at using a LVDS input for a comparator and Xilinx did it
in a demo of a SDR. They are very short on details, but they talk about
1 mV on the input. I know that's not anything special, I'm hoping to do
better, much better.

If you can keep substrate noise in check it could work. Try to remain
fully differential as much as you can. Not sure if FPGA design suites
still let you hand-place blocks so you can avoid making a big racket
right next to the ADC area.

Last week I reviewed a design with some larger FPGA on there.
What I
found fairly disgusting was how much they had to be babied with the
power sequencing. uCs don't have that problem.

If you want to work with the wrong device, then you will find it
hard to
work with. There are still single voltage devices on the
market. If
this was an old design, most likely it was a Spartan 3 or similar
era
device when they (for still unknown reasons) used three, yes, count
them, *three* voltages on the FPGA. The 2.5 volt aux supply was
there
solely for the configuration interface which was normally to a 3.3
volt
device! Only from Xilinx...

If this was a new device, then I guess they picked one based on
something other than ease of use, eh? Don't assume all FPGAs are
the
same.


Well, this guy is a real expert on high-end FPGA and the project
requires stuff with tons of horsepower.

That's fine, just don't judge all FPGAs by the ones you have seen. If
the only MCU you had worked with were ARM 11s using 3 Watts and
running
a cell phone down in 8 hours, would you think the PIC MCUs were the
same?


Well, give us all here an example of a FPGA that can fully emulate a
TSM320 and costs $3

There are a number of $3 FPGAs. I can't imagine why you would want to
emulate a DSP in an FPGA. I would rather design a project using an
FPGA. TI likely has a restriction about running their code compiled
with their tools in an FPGA softcore. So what is your project?


I wasn't referring to a specific project, just your claim that FPGA can
do the same job as processors at the same price.

Yes, that is my claim. The obvious exception is when some feature is
needed that just isn't available in an FPGA. I'm not saying *every*
project can be done better in an FPGA. I'm saying that designers tend
to just not consider FPGAs when they are often viable solutions.

In most of my apps I need much of the functionality that a decent uC
affords, like the $3 device from the MSP430 series I mentioned.

One project will probably require something of the caliber of a
MSP430F6733. Whether this kind or a DSP, what is key is that we are able
to use pre-coooked library routines. In my case for complex (I/Q) signal
processing, FFT, non-linear filtering and so on. Sometimes legacy
routines must be kept and in an FPGA that would require an IP block that
can emulate the respective processor well enough.

Ok, that is likely a no-go. If you really want to emulate a DSP chip
then an FPGA is not likely to be a useful way to proceed. Wanting to
run DSP precompiled library code is a bit of an extreme requirement. If
the customer wants a DSP, then by all means give them a DSP. But don't
automatically exclude an FPGA from the task.

Sometimes it would also be ok if there were similar pre-cooked FPGA
routines (I/Q signal processing, non-linear filters et cetera).

But what I see most is this: The respective client has in-house talent
for writing code. They are familiar with a particular architecture, have
a vast arsenal of re-usable code built up, and naturally they do not
wish to give this up. If it's a dsPIC like last year, then that goes in
there. If it's Atmel and MSP430 like this year, then that is used. Has
to be, the customer is king.

Yeah, well that is a deal killer for *any* other alternative. That is
not related to what I was saying. My point is that if you don't have
any specific requirement that dictates the use of a given chip, an FPGA
has as good a chance at meeting the requirements as an MCU or DSP. In
fact, FPGAs are what get used when DSPs aren't fast enough. My point is
you don't have to limit them to the high end. They also do very well at
the low end.

No disagreement there, programables have come a long way since the days
of GALs. Which I never used because they were expensive power guzzlers.

One other challenge that needs to be met in most of my cases is
longevity of the design. A FPGA would have to remain available for more
than just a few years. For example, one of my uC-based designs from the
mid 90's is still in production. Since I kind of had a hunch that this
would happen I used an 8051 family uC. Is there something similar in the
world of FPGA?

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Tim Williams]

"Joerg" <invalid@invalid.invalid> wrote in message
news:b91lacF5bvnU1@mid.individual.net...

One other challenge that needs to be met in most of my cases is
longevity of the design. A FPGA would have to remain available for more
than just a few years. For example, one of my uC-based designs from the
mid 90's is still in production. Since I kind of had a hunch that this
would happen I used an 8051 family uC. Is there something similar in the
world of FPGA?

Interjecting what little experience I have here;

MAX7000s are still available, and they were introduced in 1995;
http://www.altera.com/devices/cpld/max-about/max-about.html
although I think they've finally gone out of stock (not that you'd want to
use them, they also guzzle power like they're NMOS).

FLEX 10K FPGAs don't appear on their website, but they're still quite
available. Can't seem to find when they were introduced? I'm seeing
documents since at least 1996 referencing them.

At least between the big two (Altera that I know of, and I would assume
Xilinx too), FPGAs look to have excellent support over time.

And VHDL doesn't age. The library blocks might, but I'd be willing to
guess that those are synthesized as well, so as long as your toolchain
supports whatever code format, you can migrate chips easily when they do
finally die.

And really, if you have to support something for over 20 years, it's
probably time it does die and gets a redesign. Like that VAX or whatever
it was NASA's still supporting.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://seventransistorlabs.com

 

[Joerg]

rickman wrote:

On 9/7/2013 4:46 PM, Joerg wrote:
Paul Rubin wrote:
Joerg<invalid@invalid.invalid> writes:
I don't see how the equivalent of a TMS320 or a big MSP430 could fit
into one of these small Lattice devices.

I had thought the parts of those processors that would bloat up badly
(instruction decode etc.) are pretty simple so the overall effect of the
bloat is ok in the scheme of things. The parts doing the most work
(memory, arithmetic) are done in the FPGA hardware (RAM and DSP blocks,
adders connected to the LUT's somehow) as efficiently as on the MCU's.

I do think softcores seem like a silly idea a lot of the time, and am
looking forward to more low end FPGA's with MCU blocks.


Much of it has to do with legacy code. Yes, some things could even be
done more efficiently in the FPGA because you can actually streamline
the HW to the task, something neither uC nor DSP allow. For example, why
have a 32-bit HW multiplier when you know you'll never exceed 23 bits?
But legacy code won't run anymore and you need FPGA specialists to make
it all work.

No, you would need a DSP specialist. The FPGA designer only needs to
know how to code the FPGA.

So for this kind of solution in an FPGA you need a DSP specialist and an
FPGA specialist? That would be a problem.

But that is exactly the point of the FPGA in DSP apps. You code to the
app, not to a processor.

How long do the usual FPGA stay in the market? Meaning plop-in
replaceable, same footprint, same code, no changes.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

Tim Williams wrote:

"Joerg" <invalid@invalid.invalid> wrote in message
news:b91lacF5bvnU1@mid.individual.net...
One other challenge that needs to be met in most of my cases is
longevity of the design. A FPGA would have to remain available for more
than just a few years. For example, one of my uC-based designs from the
mid 90's is still in production. Since I kind of had a hunch that this
would happen I used an 8051 family uC. Is there something similar in the
world of FPGA?

Interjecting what little experience I have here;

MAX7000s are still available, and they were introduced in 1995;
http://www.altera.com/devices/cpld/max-about/max-about.html
although I think they've finally gone out of stock (not that you'd want to
use them, they also guzzle power like they're NMOS).

FLEX 10K FPGAs don't appear on their website, but they're still quite
available. Can't seem to find when they were introduced? I'm seeing
documents since at least 1996 referencing them.

Ok, sorry, forgot to say that I never use that manufacturer.

At least between the big two (Altera that I know of, and I would assume
Xilinx too), FPGAs look to have excellent support over time.

And VHDL doesn't age. The library blocks might, but I'd be willing to
guess that those are synthesized as well, so as long as your toolchain
supports whatever code format, you can migrate chips easily when they do
finally die.

But the minute a footprint changes or you have to re-compile you are
screwed in some heavily regulated markets.

And really, if you have to support something for over 20 years, it's
probably time it does die and gets a redesign. ...

Nope. Not if it's in the worlds of medical or aerospace. There you have
a huge re-cert effort on your hands for changes. New layout? Back to the
end of the line.

You also need to support very old legacy equipment with type-certified
spare parts and for those few sales you really don't want a re-cert.
Just think about the DC-3 which is still in service. Some of those are
over 60 years old. Can be worse with elevators. We have a company near
here that sometimes has to support elevators that are over a century old.

... Like that VAX or whatever
it was NASA's still supporting.

Sometimes changing is very time consuming. I recently learned that this
is even the case for alarm systems. "If we even add as much as one
capacitor for EMC we have to go through the whole insurer certification
process again".

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Stef]

In comp.arch.embedded,
Joerg <invalid@invalid.invalid> wrote:

Nope. Not if it's in the worlds of medical or aerospace. There you have
a huge re-cert effort on your hands for changes. New layout? Back to the
end of the line.

That is not always true (at least for medical equipment, no experience
with aerospace). If the change is minor enough, it may be enough to
write a rationale that explains the change and how it does not impact
the function of the equipment. If the notified body agrees with the
rationale, only a limitied effort is required to re-cert.

Sometimes changing is very time consuming. I recently learned that this
is even the case for alarm systems. "If we even add as much as one
capacitor for EMC we have to go through the whole insurer certification
process again".

Weird, I would expect a similar approach with a rationale or something
would be enough.


--
Stef (remove caps, dashes and .invalid from e-mail address to reply by mail)

Antonym, n.:
The opposite of the word you're trying to think of.