Hello,
in the manual you find an example on page 14. The idea is to blink the built-in LED.
Manual:
https://www.olimex.com/Products/OLinuXi ... O-MAXI.pdf
I tried that with a fresh Archlinux ARM installation and I'm unable to change the LED state.
Another problem is the UEXT_CS pin (Pin 10 of the UEXT connector). It should be possible to set this via GPIO but I'm unable to do so.