This weekend I decided to have a break from study and spent a couple of days designing a SMT Raspberry Pi Shield for the Blitz DAQ.  The board uses the Raspberry Pi GPIO pins and provides a 4 channel 15-bit ADC as well as 5 digital inputs (the Blitz DAQ message format allows five digital flags). 

With this shield you could remove the need for a separate Arduino and avoid the issues with Raspberry Pi GPIO on a non-realtime operation system. By using SPI for the Raspberry Pi to shield communications I'll also be able to bump the sample rate up from the Arduino / USART based configuration I've mostly been testing with.

I've got some input protection on the analogue pins - basically Zeners and PTC fuses and I'm trying to work out if I should put a buffer/follower in as well. I don't know any hard and fast rules about when this might be a good or bad idea.

I'm comfortable enough with the design that I feel I could build a prototype, however I'm just heading into my last six weeks of Uni so it will probably be a little while before get around to it!

P.S. like the Blitz DAQ software, this and the firmware will be released as open hardware when I'm happy.