Re: Single Chip ARM solution for Debian Linux?

[Luke Kenneth Casson Leighton <lkcl@lkcl.net>]

On Sun, Jul 22, 2012 at 6:42 AM, Mike Thompson <mpthompson@gmail.com> wrote:
> Does anyone know of a single chip ARM based solution that is capable
> of running a very minimal install of Debian Wheezy armel?  Perhaps a
> <100MHz armv4/v5 chip with onboard flash, 4/8/16/32 MB ram and a
> single USB peripheral port.

 mike: you're not really going to get debian into that kind of setup,
or any normal (read: standard off-the-shelf) gnu/linux distribution.
even RTEMS, a real-time OS, doesn't fit into that kind of RAM levels,
and you have to use uRTEMs instead.

 so it is a bit of a misleading question :)

 there are a number of arduino-inspired board such as one that peter
mentions, such as the olimexino, the leaflabs maple (and variants);
there are also some TI-based single-chip systems; all of them have
exceptionally good compiler support, real-time OS support and so on.

 however typically just as peter mentions there simply isn't room even
for full OSes so you have to use things like libopenstm32:
http://www.hermann-uwe.de/blog/libopenstm32-a-free-software-firmware-library-for-stm32-arm-cortex-m3-microcontrollers
- as mentioned before, whilst RTEMS is available for the STM32 even
RTEMS is quite big and for the 4/8/16 MB RAM SoCs you'll need to use
the cut-down "micro" version of RTEMS.

 lastly it is worthwhile mentioning that yes, openwrt can even now fit
into 16 or even 8mb of RAM, and that angstrom linux certainly 8 years
ago was capable of firing up in 32mb of RAM with a full suite of
PDA-style applications and even a frame-buffer-based version of
X-Windows (and probably still is if you are careful), if you
investigate further you will probably find that the only reason these
GNU/Linux OSes can fit into that kind of memory is because they're
still using the 2.4.18 to 2.4.20 linux kernel which is known (from
experience) to be trimmable down to around 600k, and so gained a
fierce reputation in the embedded world.

 bottom line is: if you're prepared to increase the RAM requirements
to say 64mb and to use debian 3.1 (*1) from over 10 years ago you
*might* get lucky, but then you may run into porting issues because
the versions of the linux kernel available at that time will not
support modern hardware, and you'll have to back-port the device
drivers.

 otherwise, just write the applications to interface directly with the
hardware, just like everyone else does.  if you want to use python,
it's possible: the leaflabs team ported an embedded version of python
(pymite) to the maple (*2)

l.

(*1) which does have a backports 2.6.18 kernel or possibly even 2.6.24
iirc on archive.debian.org but still, good luck with the drivers....
(*2) http://leaflabs.com/2011/09/pymite/