Some pins are used for all kinds of things. For example pins 0 and 1 are used by the default Serial object. This means that if you write to those pins then the serial output will be broken.
Also make sure not to use the pins that are used by the Bluetooth module.
Some pins are used for all kinds of things. For example pins 0 and 1 are used by the default Serial object. This means that if you write to those pins then the serial output will be broken.
Also make sure not to use the pins that are used by the Bluetooth module.