I'm looking for some simpls examples for writing IOP modules. I have been able to make my own IRX and set a thread in it to run. What I'm looking for are the ways to create ee side rpc interface as well as writing to memory from ee to iop and back. I'm not that great a C programmer so far and I tried looking at the pcm player and mod player but I cannot full comprehend the data transfers and rpc calls.
Have a look through ps2sdk. There are various IOP modules you can look at. For a full RPC server I suggest looking at ps2ips.irx in ps2sdk. ps2ips is the server side rpc for ps2ip.irx.