Welcome to my quick review of an inexpensive 2-channel 5V relay module controlled via RS485 bus utilizing Modbus RTU protocol. As claimed by some online sellers, this easy-to-get Modbus RTU 2-Channel ...

VCC Power Connects to 3.3V on the Pico. GND Ground Common reference ground. MISO/DO Master In Slave Out SD → Pico data line. MOSI/DI Master Out Slave In Pico → SD data line. SCK SPI Clock Clock signal ...