Hello @arkieguy if you use an M5Stack 5 / 13 should work. However if you use an M5Core2 you'll need to change the DIP switches in the COM.GPS to 16 / 17. The reason for that is that the Arduino code for M5Core2 uses GPIO 13 / 14 which translate to 16 / 17 in the module. from Arduino example for M5Stack: Serial2.begin(9600, SERIAL_8N1, 5, 13); from Arduino example for M5Core2: Serial2.begin(9600, SERIAL_8N1, 13, 14); Please also check this GPIO comparison sheet I've put together a while ago. Thanks Felix