[avrdude-dev] support for bitbanging GPIO lines through gpio-dev

[Bart Van Der Meerssche]

Hello list,

Our new Fluksometer hardware version will use a bitbanged SPI bus to 
communicate between an Atheros AR2317 WiSoC on the main board and an AVR 
on the sensor board. The AR2317 contains a MIPS 4KEc processor running 
OpenWRT.

I have used the patch of Radoslav Kolev attached to his message posted 
to this mailing list [1] as a starting point to construct a bitbanged 
SPI over GPIO Avrdude programmer using the 'deprecated' gpio-dev instead 
of gpio-sysfs. This is because the Atheros Backfire build of OpenWRT 
still uses gpio-dev for driving its GPIO pins. The patches against 
Avrdude 5.10 are available on Github [2]. Since the Fluksometer is an 
embedded device having a mere 8MB of flash, we needed to trim Avrdude as 
much as possible. The 120 and 130 patch in [2] remove all non-gpio 
programmers and small/old AVRs respectively. Applying these two patches 
reduces the avrdude/avdude.conf file size from 480k/497k to 169k/309k.

This GPIO programmer on an AR2317 flashes the AVR at about 1kB/sec, 
which is quite satisfactory.

+1 for #avrdude uses in embedded devices :-)

Best regards,
Bart Van Der Meerssche
Flukso


[1]: http://lists.nongnu.org/archive/html/avrdude-dev/2010-04/msg00003.html
[2]: 
http://github.com/icarus75/flukso/tree/develop/mote/v2/openwrt/package/avrdude/patches