It will also fail if an invalid GPIO pin number is used. PLTF_GPIO_INTR_PIN is set to 7 in the demo code, but my on Pi 4B that wasn't a valid option, and I ended up setting it to 25 and using GPIO 25 instead.

The default user account on Raspberry Pi does not have the required permissions to access the GPIO pins as necessary. If you run the app with `sudo` it will work.Sean