After my Pi arcade graphics board I thought I would take it a step further. It would be nice with a JAMMA board with a big FPGA, opto-isolated JAMMA inputs and a lot of I/O to add more functions and devices if needed.
So, I went ahead and designed one. It has the same audio amp as the Pi arcade board, it has 2×8 dip switches, all inputs from the JAMMA is opto isolated and it has one 40-pin and two 16-pin I/O ports. I also added the RAM from the Pi arcade board (512k x 8, 10ns). And the FPGA is a 55k one. Should be enough for many old games and also for many new projects with an added processor (it will probably be 100% compatible with the old Pi arcade board).
It took a few weeks to cad it (on my spare time), there are at least 150 pins for the power supply only… The FPGA has a total of 484 pins.
Mounting the FPGA was not easy, and the first attempt failed. However, after re-balling the FPGA with my soldering iron (i didn’t even think that was possible) I got a response on the JTAG chain!
I implemented a character generator in Verilog and started writing tests to read the JAMMA signals. By some reason 2P Right fails, everything else worked. Also the DIPs worked fine.
Yesterday I added a walking-one test for the RAM, and it seems the RAM is working fine as well.
Today I implemented a sound test but I didn’t test it yet. For now it should output a 1kHz sine wave. I will make it output frequencies from 20Hz up to 20kHz when I get the base going.