Thanks, I had a look on the different links you've provided.
They are using packet mode and byte based preamble and syncs.
The main issue I have is with the preamble and sync. They are very specific, different frequencies I guess and only a few bits for each part.
Is there a way to set the signal to 1/0 totally manually so I could generate the whole "packet" : set to 1, delay 207.5us, set to 0, delay 207.5us, set to 1, delay 207.5us, set to 0, delay 207.5us, set to 1, delay 625us.... etc This is the hard way, but maybe the only solution to be in accordance with this special format (picture for details).