Have had a arcade setup for many many years. Using ~2006era IPAC, WinXP machine, and Happ P360 sticks. The sticks required 5V, so I had a molex connector from PC PSU feeding that.
PC -> USB-PS2 -> IPAC -> buttons/sticks
PC PSU -> 5V/GND ... GND tied together with IPAC GND and feeding buttons/sticks, 5V feeding P360s.
In process of migrating to a new RaspPi5 setup. When I try this out, I plug the IPAC Ps2-USB cable into Rasp PI. I leave the old PC running with the molex supplying 5V. Results in IPAC not registering all buttons or being erratic. Tried same thing with laptop in place of raspPi and get same result.
Then I tried disconnecting the two P360s (s buttons only) and things work. As soon as I plug in P360 - making use of the old PCs 5V - things go wrong.
What am I missing? seems like having 5V/GND from another source shoudl be fine???
Thanks