Last updated on May 19, 2008
Tonight I did some more digging into the problems I’ve been having getting the MIDI sync working in Ivan’s P3. I had been sent some new firmware to try, and while that (in the disassembler) appears to deal with the right pins (GP0 as output, GP5:GP4 as input), it didn’t work. Tonight I did a good bit more digging and eventually ended up writing this program as a test.
Based on my understanding of how the PIC in the P3 with v1.5 PCB works, this program does the following: GP0 is set to low, then whenever GP4 changes state GP0 is changed as well, but only if GP5 is high. The end result is that on the output pin of the PIC, which connects through to the SYNC output, I basically see a mirror of the inputted sync signal whenever the sequencer is running.
I don’t think that it would be a huge stretch to write my own version of the software that is supposed to be in this PIC, but I haven’t gone that far. As far as I’m aware all I’d need to do is have each sync pulse received cause a MIDI Clock message to be sent out of GP0, and whenever GP5 goes high or low send a respective MIDI Start or Stop. That said, this P3 should really be running its official software, not my replacement stuff.
Hopefully I’ll receive some new firmware for it soon, and hopefully that firmware will do what it needs to. If I’m bored enough tonight maybe I’ll try and follow the flow through the entire program in the disassembler and figure out where it’s going wrong.