RS-485 Shield for WeMos D1 is a half-duplex RS-485 to TTL Serial transceiver board for WeMos D1 Mini (ESP8266) and WeMos C3 Mini (ESP32) microcontrollers. This board was designed mainly for easy Wifi to Modbus connectivity using HomeAssistant‘s ESPHome Modbus Component.

Features

• RS-485 chip: MaxLinear SP3485 or any other pin compatible RS-485 to TTL serial transceiver
• RS-485 connector: RJ45 socket (TE / MOLEX) or 3.5mm 3-pin screw terminal
• Supply voltage: 3.3V (from WeMos Mini microcontroller board)
• Logic level: 3.3V
• Serial interface connects directly to UART interface on the microcontroller (Serial debug should be disabled)
• Esphome pins on WeMos D1 Mini (ESP8266) boards:
  • TX: 1
  • RX: 3
  • Flow control: 2
• Esphome pins on WeMos C3 Mini (ESP32) boards:
  • TX: 21
  • RX: 20
  • Flow control: 6

Resources

• Design files on GitHub
• ESPHome ModBus Component
• ESPHome ModBus example configuration for SDM120M Energy meter
• ESPHome ModBus example configuration for 16 Channel AC Current Transformer (HDHK)

Buy

• Bare PCB: 3€
• Pre-assembled: 12€
• Pre-assembled with screw terminals: 17€
• Pre-assembled with RJ45 socket: 17€