Ethan wrote:
I'll have to dig out my harness to remember how I did it years ago, but it can't be too complicated
I found my boards and harness... turns out I recycled a PS/2 mouse cable and spiral-wrapped it alongside a custom-built DB25M cable for the parallel port. Makes sense - my old laptop had a PS/2 port on the back that never got used when I was running Daphne.
The keyboard port must not have had current limiting. If it weren't for the limited ability of modern USB ports to power external devices, I'd suggest doing that for new cables, but perhaps it might work anyway. USB is officially limited to 100mA per port until the device negotiates a higher current requirement; but even that tops out at 500mA. Having just gone over the data sheet for the ICM7218 driver chip, it appears that the current draw is lower than I initially estimated, most likely due to the effects of multiplex strobe. If I read the data sheet correctly, one ICM7218 could draw up to 300mA @ 5V if all the digits are set to '8', pushing the total draw for a scoreboard (2 chips plus LEDs) over the 500mA limit. OTOH, it might work, especially if one isn't flashing random numbers on the LEDs.
As soon as I can find a PS/2-to-USB converter dongle, I'll probably give this a go, then report back. Either way, an external 5V power supply would take care of lighting up the unit. In the meantime, if anyone else out there has a scoreboard, original or replica, please share any stories or pictures you might have. I'm really happy I can run Daphne with real external hardware, and am happy to help others to do the same.
-ethan