A friend also gave me a Caplio camera which had a time lapse function, and was then doctored to have the backlight switched off with the use of a removable 'jumper' - cheers Steve. Add another 150g to the payload....
Getting the bloody Gumstix to work is a nightmare. More instructions on how to get that going to be added later, but essentially going for the git repository method described here.
Then, JCoxon launched a balloon with live slow scan TV transmissions, in fact using a Gumstix for this.... why not eh, how difficult can it be? As it turns out, very, and the Gumstix compilations, modules, hardware and other foibles have set me back. Thanks James for the assistance and the Audiostix. :)
It should have worked, all parts are talking to each other, the loaned SSTV code compiled and seemed to work fine, the transmitter transmits, but more work is needed! dammit.
I've decided that an Arduino should be the flight computer. It has proven stability and seems quite simple to setup, with ease of programming and come in various 'flavours' and sizes - maybe a pro mini could be good - it is small and lightweight. Anyway, got the duemilanove model to play with.
Added a temperature sensor, and also thought it would be good to add a pressure sensor - Sparkfun supplied all these bits.
The main part of a payload is the GPS unit. I've been working on a sister project for an autonomous flying plane a la diydrones. This is arduino based, but also has a nice GPS unit, with a very usable connector which takes care of some tricky interfacing & voltages. Though later on this unit seemed to not get a lock - but re-soldering the antenna sorted this - pain in the proverbial.
Some problems I've encountered here are the various voltage issues of the IO lines to the arduino from the pressure sensor and my latest addition - and compass module. These require 3.3V whereas the lines are 5V - so some resistor voltage division & limiting was required.
Then, problems with the onewire dallas sensor code stopped my GPS from getting enough data to the arduino (turns out other folk have had similar problems)
so, currently I'm ditching it, as the SCP1000 module includes temperature as well as air pressure.
Some pics of the current setup:
GPS & connector:
SCP1000 pressure sensor:
Arduino, GPS, pressure and temp sensors: