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PIC vs AVR vs ARM

 
 
Miem
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      10-02-2006, 08:28 AM
Hi All,

As an amateur embedded circuit player, I have used couple of AVR and
PIC microcontrollers in the past.

In these days it is not to hard to find small, ARM based ready to use
embedded boards under $100. They seems to have faster clock speed then
most of the AVR and PIC boards.

Can anybody shortly compare ARM with PIC ad AVR interms of (a)
performance (b) software support (c) price?

Regards,

Miem

 
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Tim Wescott
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      10-02-2006, 04:22 PM
Miem wrote:

> Hi All,
>
> As an amateur embedded circuit player, I have used couple of AVR and
> PIC microcontrollers in the past.
>
> In these days it is not to hard to find small, ARM based ready to use
> embedded boards under $100. They seems to have faster clock speed then
> most of the AVR and PIC boards.
>
> Can anybody shortly compare ARM with PIC ad AVR interms of (a)
> performance (b) software support (c) price?
>
> Regards,
>
> Miem
>

(a) Significantly better. You can't beat it with an 8-bit processor.
(b) At least as good, particularly if you don't mind gnu tools.
(c) It'll be harder to really shave the pennies off in a high-
volume application, and a bare-minimum ARM board will be bigger,
more power hungry and have a higher BOM cost than a bare-
minimum AVR or PIC board.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html
 
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linnix
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      10-02-2006, 04:38 PM
> ...
> (c) It'll be harder to really shave the pennies off in a high-
> volume application, and a bare-minimum ARM board will be bigger,
> more power hungry and have a higher BOM cost than a bare-
> minimum AVR or PIC board.


AVR has wider operating voltage range than ARM, which is useful for
dealing with different logic devices.

 
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PeteS
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      10-02-2006, 08:32 PM
linnix wrote:
> > ...
> > (c) It'll be harder to really shave the pennies off in a high-
> > volume application, and a bare-minimum ARM board will be bigger,
> > more power hungry and have a higher BOM cost than a bare-
> > minimum AVR or PIC board.

>
> AVR has wider operating voltage range than ARM, which is useful for
> dealing with different logic devices.


The only technical downsides to ARM are the minimum system complexity
and power, as Tim already mentioned. As always in engineering, it comes
down to 'it depends' and the dependency is, in this case, what you need
(or want) to achieve with the system.

If you need an ultra low current system monitor, it's hard to beat the
AVR or PIC (I prefer the AVR for a number of reasons). So which is
'better' is a much harder question.

Cheers

PeteS

 
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Ulf Samuelsson
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      10-02-2006, 09:23 PM
PeteS wrote:
> linnix wrote:
>>> ...
>>> (c) It'll be harder to really shave the pennies off in a high-
>>> volume application, and a bare-minimum ARM board will be
>>> bigger, more power hungry and have a higher BOM cost than a
>>> bare- minimum AVR or PIC board.

>>
>> AVR has wider operating voltage range than ARM, which is useful for
>> dealing with different logic devices.

>
> The only technical downsides to ARM are the minimum system complexity
> and power, as Tim already mentioned. As always in engineering, it
> comes down to 'it depends' and the dependency is, in this case, what
> you need (or want) to achieve with the system.
>
> If you need an ultra low current system monitor, it's hard to beat the
> AVR or PIC (I prefer the AVR for a number of reasons). So which is
> 'better' is a much harder question.
>


Some more things that come to mind...

Size of package could be an issue as well.
Not a lot of ARM options below 48 pins.
Almost all ARM have JTAG so if you need OCD
you lose multiple pins.

Determinism when toggling I/O ports could be an issue.
The ARM has to pass through a number of interfaces
before the I/O pin is reached, and this can
take some clock cycles and add jitter.

This of course allows an AVR to run at lower clock frequqncy at
the same toggle rate.

Putting the I/O on the 32 bit ASB/AHB bus will help
but the drawback is higher capacitance on the ASB/AHB
bus which should increase power consumption.

ARM parts typically lack byte addressable EEPROM.

It is easy to prototype using DIL packages.
Normally not available for ARM.

The AVR has more (but narrower) registers
allowing global variables to be stored there.

Bit instructions.

Generally AVR code is smaller than ARM code.


> Cheers
>
> PeteS


--
Best Regards,
Ulf Samuelsson
(E-Mail Removed)
This message is intended to be my own personal view and it
may or may not be shared by my employer Atmel Nordic AB



 
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linnix
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      10-02-2006, 10:16 PM

> Almost all ARM have JTAG so if you need OCD you lose multiple pins.


That is the positive side of ARM. Jtag is always there, and reliable.
AVR Jtag, on the other hand, could be disabled, and thus un-reliable by
definition.

 
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Jonathan Kirwan
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      10-02-2006, 10:18 PM
On 2 Oct 2006 15:16:16 -0700, "linnix" <(E-Mail Removed)-for.us> wrote:

>> Almost all ARM have JTAG so if you need OCD you lose multiple pins.

>
>That is the positive side of ARM. Jtag is always there, and reliable.
>AVR Jtag, on the other hand, could be disabled, and thus un-reliable by
>definition.


Last I looked, some years ago, ARM JTAG is also documented --
including the debug interface.

Jon
 
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steve
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      10-02-2006, 10:56 PM

Miem wrote:
> Hi All,
>
> As an amateur embedded circuit player, I have used couple of AVR and
> PIC microcontrollers in the past.
>
> In these days it is not to hard to find small, ARM based ready to use
> embedded boards under $100. They seems to have faster clock speed then
> most of the AVR and PIC boards.
>
> Can anybody shortly compare ARM with PIC ad AVR interms of (a)
> performance (b) software support (c) price?
>
> Regards,
>
> Miem


AVR and PIC aren't really comparable with ARM, the first two are very
low cost/power 8 bit machines, the ARM is a higher power, higher cost
32 bit machine. If you need to make a device that needs to run on a
coin cell for 2 years, you can't pick an ARM processor, if you need a
CPU that can do real time FFT, a PIC won't do it.

 
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Buddy Smith
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      10-03-2006, 12:43 AM
steve <(E-Mail Removed)> wrote:

> AVR and PIC aren't really comparable with ARM, the first two are very
> low cost/power 8 bit machines, the ARM is a higher power, higher cost
> 32 bit machine. If you need to make a device that needs to run on a
> coin cell for 2 years, you can't pick an ARM processor, if you need a
> CPU that can do real time FFT, a PIC won't do it.


I thought so too, but the products from luminary micro
(luminarymicro.com), discussed in this newsgroup recently and in Circuit
Cellar, have changed my mind.

They make ARM CPUs with very little RAM and flash, on the cheap.... they
say less than one dollar in 10k quantities (from an advertising spiel)

ttyl,

--buddy

 
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steve
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      10-03-2006, 01:26 AM

Buddy Smith wrote:

> I thought so too, but the products from luminary micro
> (luminarymicro.com), discussed in this newsgroup recently and in Circuit
> Cellar, have changed my mind.
>
> They make ARM CPUs with very little RAM and flash, on the cheap.... they
> say less than one dollar in 10k quantities (from an advertising spiel)
>
> ttyl,
>
> --buddy


yes but they are very high power, I think 10x the power of the AVR at
1Mhz, if I remember correctly

 
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