I'm considering building some custom gizmos to connect to the gameport on my retro-hobby PC (SNES controller adapter, macro/turbo box, etc.) but I haven't been able to find much information on details such as allowed current limits.
(Just this un-cited mention on the DSLReports forums which claims "The standard operating voltage for a MIDI/Gameport is 5 Volts ± 5% and a current output of 40mA when active and 22mA when in standby.")
Given some of the fancier digital joysticks that didn't require external power supplies, I know it's possible to hang some kind of fancy load off the gameport's 5V lines, but I don't want to gamble that the SoundBlaster 16 I carefully sourced off eBay a few years ago is at least as robust as whatever combination of still-in-production USB-Gameport adapter and Raspberry Pi that I risk for development testing.
On the side of protecting the host PC, I'm hoping to find a solid source for details such as:
- Maximum safe peak current
- Maximum safe sustained current
- The DOs and DON'Ts that digital joysticks stuck to when pinouts like this one list multiple 5V supply lines and specify that each GND line is intended for a specific button.
On the side of protecting the microcontroller, does anyone have any specs on maximum observed current when the buttons are pressed or the X and Y axis lines are at the 0Ω end of their range?
(In case it's relevant, I'm hoping to use those sub-$1 Chinese STM8S boards with Sduino if the numbers check out. 16MHz should be enough to bit-bang things and you can't beat 'em for size or price.)
A citation which also has similar information on PC and PS/2 keyboard ports would be appreciated since I'm also considering building a knock-off of the Dynapoint GameStar.