To get your Sinden light gun working with your Raspberry Pi 4 Retropie build, you may need to follow these steps:
Make sure your Retropie installation is up to date. You can do this by going to the Retropie menu, selecting “RetroPie Setup,” and then choosing “Update all installed packages.”
Connect the Sinden light gun to one of the USB ports on your Raspberry Pi 4.
Reboot your Raspberry Pi to ensure that the system recognizes the light gun.
Once your Raspberry Pi has restarted, go to the Retropie main menu and select “Retropie Setup” again.
Choose “Manage Packages” and then “Manage Optional Packages.”
Look for an option related to the Sinden light gun. It might be listed as “sinden-lightgun” or something similar. Select it and choose to install it.
After the installation is complete, exit the Retropie Setup and go back to the main menu.
Navigate to the Ports section, where you should find the Sinden light gun emulator or related options. Select it to launch the configuration settings.
Follow the on-screen instructions to configure the Sinden light gun for your specific games and preferences.