Hi Uffe,
Thanks for the comments!
My initial plans were to use an RPi for the GUI, mainly for the HDMI capabilities. This is still possible, and the only reason I did not, was because I have no experience in Python. The communication between the master UI board and the "blocks of 8" sub boards will be via SPI, so using an RPi in future can be done. FYI - I've never used C++ either until last year, but have extensive experience in Basic, back through the 80's.
The main processor I'm using for both the main and sub boards is a Mega2560, which has the advantages of lots on inputs / outputs, and they are really cheap!
The intent is to use the SSL keyboard, given that the S31E keyboard cable needs to be integrated anyway, as it carries the TR address bits.
I had thought about replacing all the Computer Automation boards in the existing SSL computer, and using the Input, Output, SMPTE, etc boards, but then realised you can compress all of those in to a 2RU case with the use of a Mega2560.
One thing that makes it a little more difficult is how the SSL handles "cuts". In normal operation the VCA fader works on 0-5v which is perfect for the Mega2560 analogue inputs. However when "cut" is activated, it sets the line to 10v. Likewise this is needed on the output to activate a cut. There are a few ways around it, but I have yet to work out a design of the circuit.
The current SSL computer handles this easily with a very expensive single channel 10 bit A-D chip.
In regards to making this available, I would consider making the PCBs available for the sub-boards / master. Then a DIY build. Like Hairball with their 1176 kits.
For the software, I don't know. It would be great to make it freely available if everyone helped to develop it within this community, but would not be happy if people simply copied it and used it / on-sold it to people, as there has been a lot of work put in to developing this (presently 100s of hours).
Here's a look inside the case so far...