Dimitri
There are a few vendors that have a packaged ARM processor that is suitable for a DIY environment. Here in the US,
http://www.coridiumcorp.com/Products.php is one of them. I have two of these, the ArmExpress and the ArmExpress Lite, that I have been working with to re-brain a late 1970's automatic film processor. It used a 6802 and the processing steps were prom'd. The processing timing changed with new versions of C41 and E6 film processing and the software company that wrote the firmware disappeared in the early eighties. I have been building a daughterboard with the core support chips and then using ribbon cable and dip headers to plug into the chip sockets for the old chips to utilize most of the existing control i/o. One of the nice things is I2C support so I can use a Matrix Orbital LCD (
http://www.matrixorbital.com/) A number of these displays also have a built in interface for a 4x5 keypad array as well as 6 digital outs so two lines running Ic2 provide a 4 x 20 char display, a 20 key keypad and 6 led drivers. The 4 line displays have gotten pricey over the past year but they now also make much cheaper 2 line versions