Small project to use joysticks and buttons of my pistomachine (a DYI arcade cabinet) with the GPIO pins of a Raspberry Pi wired to an old laptop. This was necessary because the USB-to-GPIO adapter I have is very unstable and crashes very often.
It is done the right way(?). The RPi is backfeeded by an USB-to-serial cable attached to the laptop, so it is brought up and down at the same time as the laptop. The installation on the RPi memory card runs on a read-only system, so power loss is not an issue. Input follows this path:
- GPIO pins are configured with a device tree overlay (
pistomachine-keys.dts) that exposes them as a virtual keyboard through thegpio-keysdriver pistomachine-gpio-serialon the RPi reads the event device, translates codes into single-byte commands and sends them over serialpistomachine-gpio-serialon the laptop reads the serial inputs, decodes the keys, maps them to desired values, and replays them to a virtual uinput device
While harder to setup than an average userland implementation, this solution should be better because gpio-keys uses kernel features (interrupts over polling, automatic debouncing) and the terminal is set to low_latency mode. The RPi should not drain much power since it is downclocked, and both the HDMI output and the USB bus are powered off at boot.