First post in the forum, I just wanted to thank all of you for experimenting and sharing your work on connecting the MAX11300 board to the axoloti. Since I am looking for ways to extend my Eurorack with custom modules, I bought it, used @mnskll SPI code for connecting the board and @weasel79 tips and everything else was pretty straight forward. By drilling holes in the MAX11300 board, it can be easily mounted directly on the Axoloti. I connected +12V/-12V to the MAX11300 board, which is recommendable (without that, it still works, but peaks, if you disconnect cables from other CV modules, which overloads the axoloti and leads to reboot)
I share two pictures. By now I already extended the module with a second Input/Output Module, and I am going to build a third extension, just because it is easy and so powerful. Right now I am using it as Synth Voice with Gate/Pitch/FM CV In, the extension board (not on the photos) as a complex LFO generator with 6 CV outs, and by using a switch, all knobs are reassigned to control an overall Delay effect on the Synth voice and also on external audio input..
This combination is a great way to build a custom eurorack module, that can be everything you feel you are missing in the rack..