Choosing a Microcontroller for Embedded Linux?

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theawddone

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Sep 1, 2006
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For a long-term (6 months++ development, 1yr++ testing) graduate-level project, I am trying to choose a microcontroller to replace a PIC18-based system so that we can run linux.

My requirements are really only that it can run Linux 2.6+ (not a uCLinux or any linux derivative, want broadest support) and has a power footprint of less than a quarter watt when 'active'. I am not planning on doing any kind of multimedia type work, so I have no need for extra features involving LCDs, audio, or video, but I know I won't be able to find a microcontroller in this area without that kind of stuff; I just want to emphasize that my requirements are not very strict outside of power thanks for the flexibility Linux provides. It's preferred that it comes in some kind of "stamp" or single board computer (i.e. a development board), but most of these chips seem to come in at least the latter.

My current favorite option is the Atmel AP7000 (http://www.atmel.com/products/avr32/ap7/ap7_5.asp), thanks to the low power and support from the "AVR-Freaks" community. I am not really sure where to look, I just happened to stumble upon this and it had a lot less power consumption than anything else I'd seen thus far.

I have tried looking into ARM-based microcontrollers, but there are just so many choices it's very difficult to know where to look, so I was hoping to get some first (or second) hand advice about making this decision.

Any help is appreciated!
 

exdeath

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Jan 29, 2004
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Arm7 or Arm9 are a good start. ARM7TDMI is pretty popular. Those are more like GPCPUs than MCUs though.
 

Colt45

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Apr 18, 2001
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I've been playing with the AVR32's.. seem fine. You can get a little sample board, with a bunch of I/Os, 2x ethernet, usb (forget if it does master, i havent played with USB on it yet..) uh.. 3 serial ports, SD-card interface... I think the board is $70 or so:
160MHz and 2x 8MB flash, 32MB RAM.
I've got my install on the SD card, so there's no real limitation there; but depending on what you have in mind it might be short on horsepower or ram...
http://www.atmel.com/dyn/products/tools_card.asp?tool_id=4102

What are you planning on doing with it, I guess is the question.. Do you need lots of IO? Horsepower and no IO? etc.

the sheevaplug things might be worth looking into, they run a MIPS chip, fair bit faster than the AVR32's...
1.2GHz, 512MB flash, 512MB RAM. Been meaning to get one myself. Hundred bucks, But I'm not sure what they have for I/O; I'm guessing it's a lot less than the 96 pins brought out to connectors on the NGW100...
http://www.globalscaletechnologies.com/p-22-sheevaplug-dev-kit-us.aspx

So.. What do you need!?


edit: err, the sheevaplug is an ARM chip, not MIPS.
 

theawddone

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Thanks for the quick responses, I mostly just need a lot of I/O for house-keeping type work and communications, this will mostly act as a bridge to the transceiver for non-status data that will be transmitted. Interfacing will mostly be done over I2C, SPI will be used with a transceiver, and a number of GPIO's will probably be required.

The reason I didn't mention this was because all of the linux-compatible devices seem to have so many pins it doesn't really matter, and you can just use a bit-banging device driver for any bus protocol necessary.

High performance is unlikely to be necessary, I just want something that can be low power and expandable (which is basically taken care of by Linux).

I am looking for recommendations at the chip level because this will go into a full custom pcb (or a stamp will be interfaced with a full custom, like the AP7000's http://www.ic-board.de/product_info.php?info=p79_ICnova-AP7000-OEM.html).
 
May 11, 2008
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If it may help, this is my favourite at the moment. But in all honesty life has caught up with me and i have not been able to play with it yet. But the controller seems very popular and dirt cheap.


www.olimex.com/dev has a lot excellent material.

The SAM7-P256 from olimex is cheap. It is based on an arm7tdmi atmel chip :


MCU: AT91SAM7S256 16/32 bit ARM7TDMI™ with 256K Bytes Program Flash, 64K Bytes RAM, USB 2.0, RTT, 10 bit ADC 384 ksps, 2x UARTs, TWI (I2C), SPI, 3x 32bit TIMERS, 4x PWM, SSC, WDT, PDC (DMA) for all peripherals, up to 60MHz operation
standard JTAG connector with ARM 2x10 pin layout for programming/debugging with ARM-JTAG
 
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