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 Posted: May 27, 2012 - 07:27 PM |
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Joined: Aug 29, 2010
Posts: 291
Location: Dharamshala, India
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Hello,
I have a general question, how do we decide that when to go for 32 bit ARM Microcontroller or 8 bit AVR.Does it decided on the basis of COST or POWER CONSUPTION or if reqirement is small like 10 i/o control than go for AVR 8 bit 
Does AVR is as efficient for Power consumption as ARM, in small requirements Means to say are 8 bit micro as good compared to 32 bit ARM
Example :--
If we automate our home on CAN bus & i need node on my wall socket to control 2 lights & 2 fans and an AC. Then this case we shall go for ARM or AVR
Thanks in advance.
//Katoch |
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Posted: May 27, 2012 - 07:34 PM |
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Joined: Sep 04, 2002
Posts: 21258
Location: Orlando Florida
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| You are calculating a Figure Of Merit based on multiplying every factor by an importance coeffcient to this particular product. You will get different results for 1 home controller vs a commercial home controller that might be made in the 1000s. In the case of commercial products, price is the most important factor, speed might be the next. If you need the fastest cpu made, it will be more expensive. If it is battery powered, then power consumption and power saving features has a high factors. If you and your buddy are Expert AVR programmers, that's a factor in favor of AVRs. Why switch to an MSP430? Need to buy and learn another compiler, IDE, etc. This is 'system engineering'. Other factors: reliability, temperature range, maintainability etc. |
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Imagecraft compiler user
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Posted: May 27, 2012 - 11:27 PM |
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Joined: Mar 28, 2001
Posts: 20367
Location: Sydney, Australia (Gum trees, Koalas and Kangaroos, No Edelweiss)
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Quote:
how do we decide that when to go for 32 bit ARM Microcontroller
When your 8 bit chip, whatever brand, runs out of resources for the task required.
As an old guy...like the one above..  I tend to preserve my remaining working brain cells for something useful rather than learning a new architecture, new tools etc.
The learning curve can be fun but not necessarily help out with paying the bills. |
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John Samperi
Ampertronics Pty. Ltd.
www.ampertronics.com.au
* Electronic Design * Custom Products * Contract Assembly
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Posted: May 28, 2012 - 07:50 PM |
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Joined: Jul 21, 2005
Posts: 1373
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For me, the right micro is the one that results in the lowest system cost.
If I need EEPROM, USB, ethernet, etc..., I am usually better off finding a chip that integrates the features I want instead of getting the cheapest uC possible and then paying multiple times what the uC is worth on external parts.
The added benefit is that with reduce external components your system will be more reliable and you will have less duds when going through QA.
Regarding power consumption, I have no idea, everyone seems to be putting ridiculously low power consumption numbers in their product literature, usually this number is under some cherry picked circumstances that are not reflective of real world usage.
AVR is a very mature product with great support, any problem you may have has been experienced by someone else on this forum and the solution is posted. So AVR is very easy to develop for.
I do not think 32 bit uCs from any particular vendor has the level of user experience that AVR has, certainly there is no single ARM forum is not as active as AVRFreaks. You can say that 32 bit uCs are harder to develop for based on support available on the internet.
In terms of pure C coding, 32 bitters are much easier to work with as you can usually take the straightest path to solve most problems ; when in doubt make the variable a float, go ahead and call functions from an ISR, no real need to go through you code with a fine comb to squeeze out the last drop of performance, you can forgo assembly instruction, etc...
To me the absolute deliminator in deciding between 8 vs 16/32 bit is 5 volt operation. If you need 5v operation then go with an 8 bitter as most of them can work with 5v. I do not know about 16 bitters, but for 32 bitters I have only found 1 brand that can operate at 5v (there are other brands but they are not accessible to small companies) |
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Posted: May 28, 2012 - 11:33 PM |
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Joined: Jul 02, 2005
Posts: 5942
Location: Melbourne, Australia
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katochd46 wrote:
Hello,
I have a general question, how do we decide that when to go for 32 bit ARM Microcontroller or 8 bit AVR.Does it decided on the basis of COST or POWER CONSUPTION or if reqirement is small like 10 i/o control than go for AVR 8 bit
Does AVR is as efficient for Power consumption as ARM, in small requirements Means to say are 8 bit micro as good compared to 32 bit ARM
Example :--
If we automate our home on CAN bus & i need node on my wall socket to control 2 lights & 2 fans and an AC. Then this case we shall go for ARM or AVR
Thanks in advance.
//Katoch
In your household automation application, power consumption of the controller is entirely irrelevant in my opinion.
When I am faced with choosing a processor, the very first thing I do is map out the functional requirements as a means of identifying the "peripherals" required. If possible I go for internal peripherals. Only then do I consider the timing issues. If the chip cannot cut it, then I look for a faster, similarly equipped device supported by my toolchain and knowledge.
Cheers,
Ross |
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Ross McKenzie
ValuSoft
Melbourne Australia
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Posted: May 29, 2012 - 03:11 AM |
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Joined: Oct 15, 2005
Posts: 530
Location: Russia, Far East Siberia, Irkutsk
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katochd46 wrote:
Then this case we shall go for ARM or AVR
Generally it depends on a whole task.
There are a bunch of ARMs: ARM7, ARM9, Cortex-Mx and so on. I wouldn't compare AVR with general ARM.
However, ARM7 might be compared with powerful AVR (above ATmega128). But what do you think about ARM Cortex-A8 1000MHz 'FreeScale iMX535' which has a lot of peripheral modules and interfaces? 
As for me. I still prefer using AVR (even old ones such as ATmega16, ATmega8, I just have them) in I/O modules (one of them you can see in here http://www.avrfreaks.net/index.php?name ... start=1080 ). But for central control module I would choose ARM7(9). Why? Of course, I realize AVR can perform most of needed operations. But it doesn't have hardware MMC/SD interface, it cannot run tasks in RAM (loadable modules), it doesn't have hardware EMAC (I know I can use an external EMAC and PHY for AVR), it doesn't have any LCD interface (I mean good LCD, at least 272x480).
These requirements are important for me. If you don't interesting in them you should choose AVR 
Excuse me if I have said something confusing. |
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Posted: May 29, 2012 - 03:14 AM |
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Joined: Dec 18, 2001
Posts: 4711
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| ARM7 is going to EOL soon, so new learning should be focused on Cortex M0 or M3. |
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Posted: May 29, 2012 - 03:18 AM |
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Joined: Oct 15, 2005
Posts: 530
Location: Russia, Far East Siberia, Irkutsk
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valusoft wrote:
When I am faced with choosing a processor, the very first thing I do is map out the functional requirements as a means of identifying the "peripherals" required. If possible I go for internal peripherals. Only then do I consider the timing issues. If the chip cannot cut it, then I look for a faster, similarly equipped device supported by my toolchain and knowledge.
Cheers,
Ross
Very wise answer, dear Ross!
Thanks! |
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Posted: May 29, 2012 - 06:19 AM |
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Joined: Oct 15, 2005
Posts: 530
Location: Russia, Far East Siberia, Irkutsk
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stevech wrote:
ARM7 is going to EOL soon, so new learning should be focused on Cortex M0 or M3.
Yes, I know
Unfortunately, I still have LPC2478 with TFT LCD))) So, my learning is restricted to them. |
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Posted: May 29, 2012 - 07:50 PM |
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Joined: Jul 18, 2005
Posts: 62299
Location: (using avr-gcc in) Finchingfield, Essex, England
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How do you choose which car to buy?
(roughly the same question but feel free to substitute the word car with TV, microwave, smartphone, laptop, washing machine, banana, or virtually any noun you can think of) |
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Posted: May 30, 2012 - 04:59 AM |
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Joined: Dec 18, 2001
Posts: 4711
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clawson wrote:
How do you choose which car to buy?
(roughly the same question but feel free to substitute the word car with TV, microwave, smartphone, laptop, washing machine, banana, or virtually any noun you can think of)
I'd disagree with all these except for washing machine.. in the US, there are a very few manufacturers and a zillion retail brand name models. The models have the same guts, but they are finished-out/tricked-up differently. Same-same for ARM cores fitted out by Atmel and all their competitors. |
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Posted: May 30, 2012 - 08:09 AM |
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Joined: Aug 29, 2010
Posts: 291
Location: Dharamshala, India
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| thanks everyone for the reply, i got the answer. |
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