PR sent with Audio Fixes , the length counter stop conditions were wrong, this should fix a lot of looping sound issues. Parodius' sound for instance went from totally annoying to "ok" sounding
I've been using Blargg's test roms to debug the APU, the first 2 tests now pass but I am stuck at 03, if someone has knowledge about those tests, especially test 2 and 3 of 03-trigger.gb, I would be grateful if they could explain it here.
The Noise channel (4) is still often "wrong", I think the LFSR is being mistakenly switched to the 7 bit mode (the ocean waves of legend of zelda's intro sound too "metallic").
I implemented a dummy serial port that always returns "not connected" and triggers the interrupt, this fixes Alleyway and probably other games too.
Final Fantasy Legends 1 and 2 seem to be fixed after I changed the LY==LYC interrupt to trigger earlier, Mario's Picross is now also playable, but it still has some minor graphical issues (probably timing related).