Jamma to Console ConversionThis is a project to take old JAMMA compatible arcade games and operate them like cartridges in a console video game system. The game is powered off of an ATX power supply, the video is converted to NTSC for display on a television and an adapter converts the signal from NES Advantage controllers.
[edit] PowerJAMMA requires the following:
All of which are available from an ATX Power supply. I removed all extra wires from the power supply, leaving only one of each voltage required. [edit] Soft PowerI left the +5v standby and the soft power lines accessible. Currently the soft power line is tied directly to ground and the standby is unconnected, leaving full power control to the hard switch on the back of the PSU. The plan is to eventually power the PIC doing the controller conversion from standby and attaching it to the soft power line, allowing the unit to power up when a button is pushed and power down either by an inactivity timeout or special button combination. [edit] VideoJAMMA video is a component RGB and composite sync signal for direct connection to a monitor. The video timing and resolution is suitable for pretty simple conversion to NTSC. I took the video conversion circuit from an Engaget Article I found when researching the AD725 RGB to NTSC/PAL converter. Rather than re-invent the wheel I used the PCB from the article directly. I found that for both games I tested, KLAX and Super Tetris, the RGB signals were over driving the AD725 resulting in fully saturated red and bright white both turning pink. I had to add 1k trim pots in each signal line which, in concert with the termination resistors on the video board, divide the signal voltage to a better level. [edit] Converter Board
[edit] Video Test
Most JAMMA games have a test mode enabled by a DIP switch, jumper or the test pin on the standard JAMMA harness. A color test screen is common. Above is the KLAX video test. [edit] AudioEach JAMMA board provides an amplified mono signal with on-board volume control for direct connection to the speakers in the cabinet. While some suggest connecting this straight to the television line in with the volume turned all the way down I didn't want to risk that (There is probably protection on the line in, but I don't know). For the time being the audio out is connected to a small PC speaker. [edit] Controls
All JAMMA projects I have seen just use a set of arcade style buttons or a game controller like the Neo-Geo, which has all of the buttons in parallel, wired right to the board. I chose the stylish route and selected classic, unmodified, NES Advantage controllers. They are awsome. The NES controller is essentially a serial device (they contain a single latching parallel input shift register) and is unsuitable for direct connection to JAMMA. The simplest solution is to use a microprocessor to convert. I used a PIC 16F688. The PIC (Small top board) reads the inputs from the 2 controllers in serial, then shifts them back to a latching serial to parallel output shift register (Etched bottom board). I could have done this with all discreet components, but the PIC offers flexibility like button remapping and soft power control. The parallel out board is 32 output, only 20 of which are used. I just have a bunch of these boards on hand for use in whatever. [edit] Converter Board
The PIC has a serial port too, which outputs serial data when a debug build of the firmware is loaded. The converter samples the buttons at about 500Hz with debug output enabled (a lot of printf's and serial output) and at about 2Khz with the release build. I haven't done a double-blind test, but I think that you can feel the difference. [edit] Button Test
[edit] CaseAll parts are stuffed into a large ATX tower case. This is pretty ugly but it gets it off the work bench and into the living room.
[edit] Future WorkWhile this project may be 'Done' future work I could do includes:
|