Hello @mmarks3141, I am just learning about nRF52840. My IDE is Eclipse/Sloeber and Arduino NANO BLE 33. And I do not want to use the mbed-OS, because it destroys the timing of my self developed libraries running on any Arduino-Board. Your question is about using a serial interface, which depends on the firmware of your board. If it is mbed-OS, please look to the documentation of mbed: https://os.mbed.com/handbook/Serial. If it is not mbed-OS, look for the resources of Your boards firmware/libraries. For me (Arduino), it would be the initialization with Serial.begin(bitrate) in setup() and using Serial.print() for the output somewhere in loop(). By the way, thanks to @NeverDie for the examples.