Would this just be solely for the Saturn or a more universal approach for other game consoles as well? If the latter, a few more things need to be taken into consideration, such as sync.
Would be intended for universal use. Any console that can output 15khz viaSCART which is pretty much all of them before the HD era.
As for sync, the
LM1881 IC strips C-Sync (suitable for JAMMA) from the composite video signal from SCART. In the project above, we repuposed the
Sync Strike to which does just that to suit our needs. Here is a diagram that shows from the
SCART pins which one has the composite signal (pin 19):
How do you want controls to work? Directly from the Saturn as normal or are you wishing to convert and connect the inputs from the Saturn to the jamma edge so that the arcade cabs controls can be used? If the latter this makes it a much less trivial task.
Neither but much closer to the latter.
We just need terminals for each button that can map to U, D, L, R, Start, B1-B3 on the JAMMA edge. Then map B4-B6 to a kick harness connector. Inputting into these terminals can be achieved with pad-hacking of actual controllers. But the more desireable way is to use a multi-console PCB like the MC Cthulhu or Brook Retro. Interfacing those multi-console PCB's to the 2x10 pin header that is becoming the standard for multi console PCB's (NES, MD, SNES, TG16, Dreamcast, PS1, PS2, XBOX OG, etc) makes this really simple.
The
PB.JAMMA fingerboard implements this beautifully.
Wouldn't an audio amp also be needed, to convert the line level audio output of the Saturn to speaker level which most cabs expect?
Absolutely would be needed. So from the SCART connector, the desire would be to route the stereo line-level output to solder points where the user can,
- Solder in panel mount 3.5mm pcb mount jack. Connect a stereo 3.5mm jack cable to feed into an external amp such as a TDA2822M
From there, the user can downmux the amped stero signal to amped mono through a simple resistor network. The fingerboard will then need an input for which the user can solder in that amped mono signal to be routed to the corresponding pins on the JAMMA edge connector.
I'd be happy to design something if you could assist with supplying me with PCB mount scart connectors. They're mostly discontinued and really hard for me to obtain in Australia.
These are pretty easy to get. Order
a pair or two from here and I'll pay you for it.
The PB.JAMMA fingerboard is IMO the best one out there. Check out this
video where the design considerations are discussed. Effectively, for this effort, the ideal is to copy that design completely, adding in the ability to:
- Integrate a pcb mountable SCART connector
- Integrate the LM1881, resistors, capactiors to strip C-Sync from the composite signal, then route C-Sync to the JAMMA pin
- Integrate the THS-Series amp, resistors, and capacitors to amp RGB, then route RGB to the JAMMA pins
- Route L/R audio to a pcb mountable 3.5mm stereo jack
- Have terminals to for amped mono input which then are routed to the corresponding JAMMA pins
If the controller interface for the PB-JAMMA can be emulated precisely, not much other work is needed for controls. The only other consideration would be form factor. If you can fit all onto a PCB that can be assembled into a fairly small project box, would make it more pleasant for the DIY guys.
Thanks Frank! Keep the questions/comments coming.