actually that's wrong. That's the pin for the switch, not the LED. The LED on Bela cape Rev B (the only ones ever available on the market) is not accessible through the headers. Rev C capes will have on-board LEDs and these will go on accessible pins. For now, you can change these lines in Bela/core/PRU.cpp to use a GPIO of your choice.
const uint32_t userLed3GpioBase = Gpio::getBankAddress(1);
const uint32_t userLed3GpioPinMask = 1 << 24;
