On the build of the RasPiSNES, some design decisions were made considering the needed connections, and based on the projects incorporated here, namely gamecon_gpio_rpi.
To drive the controllers, the flat cable that was connected to the original SNES board was used, keeping the front plate almost intact. The bonus in using this connection was to get the SNES power led acting as it should.
To show those connections, below are the representation of the RPi header, at left, and the flat cable that came from the front panel, at right, to which the gamepads are connected.
Control Pad connections
For the hotkeys, I was considering the use of an old usb keyboard, but it would kill a good usb port, and to keep it simple I discarded the possibility of an usb hub. Luckily, as only four GPIO pins were used for the two gamepad ports, thirteen remained free!
As the RPi allows for very easy GPIO access with C, C#, python and even shell, among other languages, lets put these pins to work. It is always good to use some spare parts we have as result of some years ofThe default operations until this point were based on these keyboard keys:
collecting junk electronics work, so I took some push-buttons for the essencial operations needed: to pause and manage savegames.
- Escape: Exit the retroarch emulator and get back to emulationstation.
- Map to EJECT on console.
- H: Reset the current the retroarch emulated console.
- Map to RESET on console.
- F2, F4: Save and load games.
- Map to SAVE, LOAD on the hotkeypad.
- F6, F7: Change the current.
- Map to SLOT-, SLOT+ on the hotkeypad.
- P: Pause games.
- Map to PAUSE on the hotkeypad.
Note: I had to remap key F4 to F3 for game load in retroarch.cfg, so if this button got pressed while in emulationstation, it does not quit to the shell. This is quite easy:
input_load_state = f3
These hotkeys are located as hidden as possible at first sight, on the back of the console, and their connections go as this:
Power and Hotkeys
To protect the RPi from some misconnection, I have added a bunch of 10kΩ resistors inline with the pushbuttons. The python script that drive the keys make use of the internal 60k pull-ups, so these were not needed externally.
To make the keys work, the script must be running as user root. As the RetroPie script can make the emulator start on boot, it is only a matter to find where it calls the emulator and start it before:
# in fileThe remaining cables (USB, Audio, LAN, Composite) are only passive connections, so no interface is internal, and all ports remain accessible (including one self-made extension for the SD slot).
# insert this line..
sudo python /home/pi/rpi-gpio-SNES-commands.py &
# ... before the call to the emulator