Written by: Newton C. Braga
 M5Stack M121 4-Channel Relay Module (STM32) is compatible with M5Stack core and core2 series, with 4-channel mechanical relays (NO, COM). This module features an STM32F030F4 main control chip, 5VDC to 24VDC power input interface, and an I2C communication interface. The 4-channel relay module supports I2C protocol, 24W maximum load (DC 24V@1A), and DC control. Typical applications include on/off control, solenoid valve control, and DC control load on/off.