My setup isn't ready yet, so I haven't looked into the code, but should do so within two weeks. Take a look here: http://www.ucapps.de/mbhp/mbhp_scan_matrix1.pdf It looks like you can leave (or better must leave) the 220 Ohm resistors of the DOUT out. Wish I looked at that before, since mine are already in. The replacement of the diodes can be in two ways, and you can set SM_SWAP_CR accordingly. As you made it now, that value should be changed to 1. For your setup it is 4 times this one, with 4 different DIN's. I should check what influence not having the other 3 DOUTs or alternatively, not using them will have on the messages send. It should have no influence, but i'm not sure how it's works in total.