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Groups > comp.arch.embedded > #13136 > unrolled thread
| Started by | Joerg <invalid@invalid.invalid> |
|---|---|
| First post | 2013-08-19 13:14 -0700 |
| Last post | 2013-09-02 22:27 +0200 |
| Articles | 6 on this page of 146 — 17 participants |
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AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-08-19 13:14 -0700
Re: AREF bypass capacitance on ATMega2560? John Devereux <john@devereux.me.uk> - 2013-08-20 20:16 +0100
Re: AREF bypass capacitance on ATMega2560? Vladimir Vassilevsky <nospam@nowhere.com> - 2013-08-21 14:47 -0500
Re: AREF bypass capacitance on ATMega2560? Jim Stewart <jstewart@jkmicro.com> - 2013-08-21 13:18 -0700
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-08-21 16:38 -0700
Re: AREF bypass capacitance on ATMega2560? "Tim Williams" <tmoranwms@charter.net> - 2013-08-21 21:30 -0500
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-08-22 10:51 -0700
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-06 16:26 -0400
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-06 13:33 -0700
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-06 17:12 -0400
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-06 16:10 -0700
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-06 23:59 -0400
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-07 08:10 -0700
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-07 13:03 -0400
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-07 10:59 -0700
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-07 14:54 -0400
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-07 12:39 -0700
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-07 16:44 -0400
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-07 14:48 -0700
Re: AREF bypass capacitance on ATMega2560? "Tim Williams" <tmoranwms@charter.net> - 2013-09-07 17:10 -0500
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-07 15:34 -0700
Re: AREF bypass capacitance on ATMega2560? Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2013-09-08 00:57 +0200
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-07 16:56 -0700
Re: AREF bypass capacitance on ATMega2560? Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2013-09-09 17:07 +0200
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-09 10:19 -0700
Re: AREF bypass capacitance on ATMega2560? Paul <paul@pcserviceselectronics.co.uk> - 2013-09-09 20:27 +0100
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-09 12:55 -0700
Re: AREF bypass capacitance on ATMega2560? Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2013-09-11 09:44 +0200
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-11 07:27 -0700
Re: AREF bypass capacitance on ATMega2560? Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2013-09-13 12:42 +0200
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-14 11:56 -0700
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-07 19:38 -0400
Re: AREF bypass capacitance on ATMega2560? Paul Rubin <no.email@nospam.invalid> - 2013-09-07 17:39 -0700
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-07 23:20 -0400
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-08 07:41 -0700
Re: AREF bypass capacitance on ATMega2560? krw@attt.bizz - 2013-09-07 11:17 -0400
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-07 13:23 -0400
Re: AREF bypass capacitance on ATMega2560? krw@attt.bizz - 2013-09-08 11:19 -0400
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-08 14:03 -0400
Re: AREF bypass capacitance on ATMega2560? krw@attt.bizz - 2013-09-08 19:42 -0400
Re: AREF bypass capacitance on ATMega2560? Paul Rubin <no.email@nospam.invalid> - 2013-09-08 17:18 -0700
Re: AREF bypass capacitance on ATMega2560? krw@attt.bizz - 2013-09-09 13:13 -0400
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-10 20:21 -0400
Re: AREF bypass capacitance on ATMega2560? krw@attt.bizz - 2013-09-10 23:42 -0400
Re: AREF bypass capacitance on ATMega2560? John Devereux <john@devereux.me.uk> - 2013-09-07 09:24 +0100
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-07 10:00 -0400
Re: AREF bypass capacitance on ATMega2560? krw@attt.bizz - 2013-09-07 11:32 -0400
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-07 13:35 -0400
Re: AREF bypass capacitance on ATMega2560? krw@attt.bizz - 2013-09-08 11:30 -0400
Re: AREF bypass capacitance on ATMega2560? Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2013-09-09 09:56 -0400
Re: AREF bypass capacitance on ATMega2560? Robert Wessel <robertwessel2@yahoo.com> - 2013-09-12 11:50 -0500
Re: AREF bypass capacitance on ATMega2560? Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2013-09-12 15:06 -0400
Re: AREF bypass capacitance on ATMega2560? Piotr Wyderski <peter.pan@neverland.mil> - 2013-09-12 14:57 +0200
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-13 00:21 -0400
Re: AREF bypass capacitance on ATMega2560? Piotr Wyderski <peter.pan@neverland.mil> - 2013-09-13 14:08 +0200
Re: AREF bypass capacitance on ATMega2560? Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-09-13 15:15 +0100
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-13 11:46 -0400
Re: AREF bypass capacitance on ATMega2560? Piotr Wyderski <peter.pan@neverland.mil> - 2013-09-13 18:43 +0200
Re: AREF bypass capacitance on ATMega2560? Piotr Wyderski <peter.pan@neverland.mil> - 2013-09-13 19:14 +0200
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-13 15:26 -0400
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-13 15:24 -0400
Re: AREF bypass capacitance on ATMega2560? David Brown <david.brown@removethis.hesbynett.no> - 2013-09-13 20:22 +0200
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-07 09:32 -0700
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-07 13:44 -0400
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-07 12:46 -0700
Re: AREF bypass capacitance on ATMega2560? Paul Rubin <no.email@nospam.invalid> - 2013-09-07 13:33 -0700
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-07 13:46 -0700
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-07 17:05 -0400
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-07 15:23 -0700
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-07 19:02 -0400
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-07 16:45 -0700
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-07 23:16 -0400
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-08 08:05 -0700
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-08 14:27 -0400
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-08 12:56 -0700
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-10 23:07 -0400
Re: AREF bypass capacitance on ATMega2560? Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-09-11 10:05 +0100
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-11 07:49 -0700
Re: AREF bypass capacitance on ATMega2560? Paul <paul@pcserviceselectronics.co.uk> - 2013-09-11 16:54 +0100
Re: AREF bypass capacitance on ATMega2560? "Tim Williams" <tmoranwms@charter.net> - 2013-09-11 11:25 -0500
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-11 09:49 -0700
Re: AREF bypass capacitance on ATMega2560? krw@attt.bizz - 2013-09-08 11:40 -0400
Re: AREF bypass capacitance on ATMega2560? krw@attt.bizz - 2013-09-08 11:38 -0400
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-08 09:34 -0700
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-08 14:29 -0400
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-08 13:01 -0700
Re: AREF bypass capacitance on ATMega2560? krw@attt.bizz - 2013-09-08 16:22 -0400
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-10 23:09 -0400
Re: AREF bypass capacitance on ATMega2560? krw@attt.bizz - 2013-09-08 16:15 -0400
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-08 14:20 -0700
Re: AREF bypass capacitance on ATMega2560? krw@attt.bizz - 2013-09-08 18:15 -0400
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-08 15:57 -0700
Re: AREF bypass capacitance on ATMega2560? krw@attt.bizz - 2013-09-08 19:46 -0400
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-08 17:15 -0700
Re: AREF bypass capacitance on ATMega2560? krw@attt.bizz - 2013-09-08 20:20 -0400
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-09 07:17 -0700
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-09 12:17 -0700
Re: AREF bypass capacitance on ATMega2560? krw@attt.bizz - 2013-09-09 19:30 -0400
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-09 16:38 -0700
Re: AREF bypass capacitance on ATMega2560? krw@attt.bizz - 2013-09-10 14:02 -0400
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-10 23:41 -0400
Re: AREF bypass capacitance on ATMega2560? krw@attt.bizz - 2013-09-11 00:04 -0400
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-11 07:53 -0700
Re: AREF bypass capacitance on ATMega2560? krw@attt.bizz - 2013-09-11 21:50 -0400
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-12 09:58 -0700
Re: AREF bypass capacitance on ATMega2560? krw@attt.bizz - 2013-09-12 18:54 -0400
Re: AREF bypass capacitance on ATMega2560? Piotr Wyderski <peter.pan@neverland.mil> - 2013-09-12 16:17 +0200
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-12 10:03 -0700
Re: AREF bypass capacitance on ATMega2560? Piotr Wyderski <peter.pan@neverland.mil> - 2013-09-12 19:24 +0200
Re: AREF bypass capacitance on ATMega2560? Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2013-09-12 20:38 +0300
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-12 11:23 -0700
Re: AREF bypass capacitance on ATMega2560? Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2013-09-12 22:36 +0300
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-12 12:41 -0700
Re: AREF bypass capacitance on ATMega2560? Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2013-09-12 23:08 +0300
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-12 11:19 -0700
Re: AREF bypass capacitance on ATMega2560? krw@attt.bizz - 2013-09-12 18:59 -0400
Re: AREF bypass capacitance on ATMega2560? Piotr Wyderski <peter.pan@neverland.mil> - 2013-09-13 13:00 +0200
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-14 12:05 -0700
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-12 16:03 -0400
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-12 14:42 -0700
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-13 00:24 -0400
Re: AREF bypass capacitance on ATMega2560? Piotr Wyderski <peter.pan@neverland.mil> - 2013-09-13 14:27 +0200
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-14 12:07 -0700
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-15 02:26 -0400
Re: AREF bypass capacitance on ATMega2560? krw@attt.bizz - 2013-09-15 09:51 -0400
Re: AREF bypass capacitance on ATMega2560? krw@attt.bizz - 2013-09-13 20:06 -0400
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-07 16:50 -0400
Re: AREF bypass capacitance on ATMega2560? Paul Rubin <no.email@nospam.invalid> - 2013-09-07 14:33 -0700
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-07 19:07 -0400
Re: AREF bypass capacitance on ATMega2560? Paul Rubin <no.email@nospam.invalid> - 2013-09-07 16:31 -0700
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-07 23:38 -0400
Re: AREF bypass capacitance on ATMega2560? Paul Rubin <no.email@nospam.invalid> - 2013-09-08 20:19 -0700
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-10 23:36 -0400
Re: AREF bypass capacitance on ATMega2560? krw@attt.bizz - 2013-09-08 11:46 -0400
Re: AREF bypass capacitance on ATMega2560? krw@attt.bizz - 2013-09-08 11:36 -0400
Re: AREF bypass capacitance on ATMega2560? John Devereux <john@devereux.me.uk> - 2013-09-08 09:04 +0100
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-08 13:42 -0400
Re: AREF bypass capacitance on ATMega2560? John Devereux <john@devereux.me.uk> - 2013-09-08 19:04 +0100
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-08 07:29 -0400
Re: AREF bypass capacitance on ATMega2560? John Devereux <john@devereux.me.uk> - 2013-09-09 08:56 +0100
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-10 23:54 -0400
Re: AREF bypass capacitance on ATMega2560? krw@attt.bizz - 2013-09-08 16:24 -0400
Re: AREF bypass capacitance on ATMega2560? Ulf Samuelsson <ulf_samuelsson@invalid.telia.com> - 2013-09-07 20:11 +0200
Re: AREF bypass capacitance on ATMega2560? rickman <gnuarm@gmail.com> - 2013-09-07 15:06 -0400
Re: AREF bypass capacitance on ATMega2560? Joerg <invalid@invalid.invalid> - 2013-09-07 12:54 -0700
Re: AREF bypass capacitance on ATMega2560? Ulf Samuelsson <ulf_samuelsson@invalid.telia.com> - 2013-09-02 22:27 +0200
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| From | rickman <gnuarm@gmail.com> |
|---|---|
| Date | 2013-09-10 23:54 -0400 |
| Message-ID | <l0opf7$3pb$1@dont-email.me> |
| In reply to | #13412 |
On 9/9/2013 3:56 AM, John Devereux wrote: > rickman<gnuarm@gmail.com> writes: >> >> I won't pretend that an FPGA is the right solution for every task. >> But I think MCUs are often used because that is what the designer is >> used to and FPGAs aren't understood well enough to consider. Is >> "enough" RAM more than what a given FPGA has? I don't know, how much >> RAM do you really need? Most MCU projects I have worked on never had >> a realistic RAM estimate, it was all by the seat of the pants. > > It's not always known how much you need, you discover things during > development, rework algorithms, sometimes trade RAM for speed. Customers > want more features. Yes, that is another way of saying "we don't want to design the thing, let's just code it and see how it works." My point is when asking software folks how much RAM they need they look off to the corner of the room for a moment and then give me a number. I'm sure there are those who know how to estimate realistically, but it's not common. So they just want more than they think they *might* need. I'm sure a *lot* of RAM goes unused in most MCU designs. Someone in this thread would refer to that as silicon inefficiency. >> The fact that code uses RAM makes it harder to estimate. FPGAs are a >> lot easier to design with in that regard. RAM quantities have to be >> known exactly. > > Hmm, now that really sounds like turning a constraint into a feature! No, it is a statement that you have to size a buffer to design it into hardware just like to do in software. But in software realistic estimates are often put off and the numbers are played with until the design is done. If you blow your RAM budget on an MCU you need to use the next bigger one. Fine, but then you have a new BOM cost. Same with FPGAs, but hardware designers are used to actually coming up with hard numbers before they start. No, this is just a statement that when doing hardware design it is customary to actually spec out all the details. That is another reason why FPGA designs typically have fewer issues in test and integration. -- Rick
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| From | krw@attt.bizz |
|---|---|
| Date | 2013-09-08 16:24 -0400 |
| Message-ID | <05np29hie1u5t773tv0alh94o5cvd0g2jp@4ax.com> |
| In reply to | #13390 |
On Sun, 08 Sep 2013 13:42:04 -0400, rickman <gnuarm@gmail.com> wrote: >On 9/8/2013 4:04 AM, John Devereux wrote: >> rickman<gnuarm@gmail.com> writes: >> >>> 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 $3 however, >>>>> you can get a chip large enough for a CPU (with math) and room for >>>>> your special logic. >>>> >>>> I've never used an FPGA, microcontrollers have increased in speed faster >>>> than my needs so far. So I can usually bitbang everything or use a >>>> peripheral. I used PLDs for glue logic back in the day but that's it. Oh >>>> and I bought a small xilinx dev kit which I got to make a led flash then >>>> put in a drawer for 15 years. >>> >>> So your use of MCUs is based on inertia? >> >> Partly I suppose. >> >> Or I could say that my projects so far all require a microcontroller >> anyway, and it seemed likely that a separate FPGA was always going to be >> more expensive than, say, choosing a faster CPU. >> >> A STM32F4 can bitbang a PIO at 84MHz. (It can't do anything else then, >> but still...) > >I think what you are saying is that the MCU is a key part of your design >and you use a lot of code in it. Ok, if your emphasis in on using a >commercial MCU that will do the job. But unless your MCU needs are just >too large for something that fits in an FPGA, you have it backwards in >my opinion. Why have both when you can just use an FPGA? First, you're assuming an FPGA (hammer). Second, you're going to need a bigger FPGA (even bigger hammers aren't free).
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| From | Ulf Samuelsson <ulf_samuelsson@invalid.telia.com> |
|---|---|
| Date | 2013-09-07 20:11 +0200 |
| Message-ID | <l0fq7q$qvu$1@speranza.aioe.org> |
| In reply to | #13337 |
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
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| From | rickman <gnuarm@gmail.com> |
|---|---|
| Date | 2013-09-07 15:06 -0400 |
| Message-ID | <l0ftg3$7tj$1@dont-email.me> |
| In reply to | #13352 |
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 $10 MCU+FPGA space. So get out there and explain it to your management! Otherwise you lose design wins to softcores which get cheaper every day. -- Rick
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| From | Joerg <invalid@invalid.invalid> |
|---|---|
| Date | 2013-09-07 12:54 -0700 |
| Message-ID | <b91eiuF40kgU1@mid.individual.net> |
| In reply to | #13352 |
Ulf Samuelsson wrote: [...] > > I came to the conclusion that an MCU company cannot compete with an FPGA > company unless the programmable logic part is only a small percentage of > the die. > They can compete, with the peripherals. But those have to be of good performance and most of all versatile enough. Some things can probably be achieved in simple ways. For example, by providing the option to map two pins per ADC channel for folks who need it to be low noise. > It would make sense to have a 5 kgate FPGAs in a modern micro. > Bingo! That would be fantastic. > The Xilinx Zync and Altera SoC are nice tries, except that most > of the standard peripherals suck and it is still beyond the price > most customers I've seen are prepared to pay. > I hope this doesn't rub you the wrong way but Atmel often ain't that great either when it comes to peripherals. When I looked at the "reference" in the ATMega2560 that we just designed in I almost got sick. In the relayout we piped in our own reference. -- Regards, Joerg http://www.analogconsultants.com/
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| From | Ulf Samuelsson <ulf_samuelsson@invalid.telia.com> |
|---|---|
| Date | 2013-09-02 22:27 +0200 |
| Message-ID | <l02sc0$h76$1@speranza.aioe.org> |
| In reply to | #13141 |
Vladimir Vassilevsky skrev 2013-08-21 21:47: > On 8/19/2013 3:14 PM, Joerg wrote: > > > Folks, > > What's the usual capacitance? > > 0.1uF > > > Any stability issues there? > > Nothing special. > > > I was planning > > on using a 1uF X7R ceramic cap on the AREF pin of an ATMega2560, in > > order to be able to use its internal bandgap reference. > > Do not. Use Vcc as reference. > Internal reference is inaccurate. > I remember a customer design where the Vcc rippled between 3 and 5 Volt. Was cheap, but then using Vcc as a reference is NO GOOD. BR Ulf Samuelsson > > I saw people > > using 0.1uF and 0.47uF. The datasheet is silent about stuff like that, > > as usual. > > It doesn't really matter. > > Vladimir Vassilevsky > DSP and Mixed Signal Designs > www.abvolt.com > >
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