After our meeting with Ytec and seeing the Plan-B@work we spend some time reverse engineering the signals between a HP7500A printer and the CN642 Head.
All working files will be uploaded to a Google drive so other can look at the data.
Appart from the low speed signals < 1Mhz there are 4 LVDS channels (1 clock and 3 data) we added a LVDS receiver to the breakout to be able to grab these signals. It seems there is no encription and it looks like a straight forward shift register (at least for the black) the other 2 LVDS channels control the other 3 colors. Allot more looking at bits is needed..
Feel free to dig through the files in the google drive and dont hesitate to comment. More files will be added over time.