How things look : How things sound : http://www.fileden.com/files/2008/4/21/1876835/MD2YM2413.OGG Some older pics of WiPness : http://www.fileden.com/files/2008/4/21/1876835/BoardOverview.jpg http://www.fileden.com/files/2008/4/21/1876835/YM2413audioProgress.jpg http://www.fileden.com/files/2008/4/21/1876835/YM2413audioProgress0.jpg http://www.fileden.com/files/2008/4/21/1876835/YM2413mod.jpg http://www.fileden.com/files/2008/4/21/1876835/MD2YM2413WiP.jpg Now I get full FM sound in SMS games, and I think I can use it while in MD mode also, I need to experiment a little. I will NOT be doing this, unless you pay me a ton of money, it is rather pain in the ass to do
with those 4 logic chips you can see... things are directly wired to Z80, and react on the same I/O addresses as the original would in JP SMS. I'm preparing a schematic soon, which is based on one by Eviltim / Viletim (but adapted to MD2 with CCAM) which in turn is probably based on original FM module.
veroboard will result in a big and clunky design that is difficult to mount, make it more immune to noises and have top cover still fit on the unit
..I meant "what equations did you use"? Do you have the enable flag and detection bits? I assume you're using a 74139/244 for decoding and detection bits but I can't see what the other chips are. Looking at Enri's SG-1000 and FM-70 schematics it's: /kbsel = A6 & A7 & !/IORQ "/ymsel" = !/kbsel & !A2 & /RD & !/WR & !A1 Removing R/W strobes (/WR should strobe the chip anyway), a 74138/238 can decode both the YM and flag. Adding a 74173 should fit the flag, detection bits AND analog switch using a couple passives for tricks. Edit: Everything can also fit in any unregistered (for the tri-state control) PAL using a latch instead of register flag.
I could have used a 74xx125 instead of 74xx244 but I just did not have anything available... I desoldered that 244 from a 486 mobo... That line going from 244 to 2x resistors and then to opamp part silences the awful amount of hiss the YM2413 generates when chip is not used. Only negative effect is that you hear a pop when chip is enabled/disabled, only game I tried that enables/disables the chip is Alex Kidd the Lost Stars, it happens when there's speech being played so you get a crack in the beginning and end of a sample.
