Thank you guys for the likes and the kind words!
I only slapped the thing together with great hard and software from midibox and the ideas on the forum here. It works like this:
Midibox (
www.uCApps.de and
MIDIbox Forum) is a non-commercial diy platform. It is comparable to arduino, but fully dedicated to midi applications. Great sequencers, controllers, SID synthesizers out there. The hardware is modular. You buy the pcbs you need from
mbhp.avishowtech.com-Home (in oklahoma), get your parts from any electronics store and solder the lot together. You download a firmware and upload it to the processor board. That has 2x midi in/ out and usb. You will need a certain level of experience with electronics and soldering, but you don't need to be an accomplished electronics engineer.
So I bought the core LPC17 module, a DIO matrix module (DIN would also work), an SD card adapter from chinabay plus a sdcard, a bunch of rotary encoders and a nice plastic case. Soldering guides are on ucapps.de. The firmware is midibox NG, a scalable platform for any kind of midi controller you can imagine. In this case six or more rotary encoders, the LCD is not really necessary, but was in there already.
Then find out what midi messages should be sent to control the Axe FX parameters. There is some documentation on the wiki, but I found that Axe Edit does things differently - easier for an amp style controller. Once you have the sysex messages, you put them into a configuration file. Then the software will send out the proper sysexes when you turn the knobs. I configured the midibox to just forward incoming midi signals to the axe. So it works with a floorboard as well!
That's the basics, just pm me if you want more details.
BTW, I "spied" a little on the communication between Axe FX and Axe Edit. I hope FAS does not take this as reverse engineering or some other break of their ownership rights. If they don't like it, just tell me and I will take it down.
