RPM872-H7 Overview
Pin No 1, 4 Terminal GND Circuit Function GND Pin1 and Pin4 must be connected to the ground. VIO Supply voltage for I/O pins (PWDOWN, RXD, TXD) 2 VIO 3 VCC VCC Supply voltage for Transceiver circuits. For preventing from infection, connect a capacitor between VCC(3pin) and GND(4pin).