This is my second version of the ESP Modbus board (first version: https://www.pcbway.com/project/shareproject/ESP8266_Modbus_board.html).

I use this board to read Modbus RTU serial devices and convert the messages to MQTT. My ESP8266 sketches can be used with either the version 1 board and this version 2 board as well. Please check my example projects in the linked repositories below:

Difference between version 1 and version 2:

• Version 1 uses a Hi-Link mains to 5V power supply (and mains fuse a varistor for protection).
• Version 2 accepts either 5V input, or other DC input and has a footprint for a small 4 pin DC-DC buck converter.

I designed version 2 board for 2 main reasons:

• On some of my projects, I use a separate 5V power supply (to power multiple boards), or I have other DC power source (e.g. 24V). Therefore I don't need the mains power supply
• The Hi-Link power supply can only provide enough power for the ESP and in some of my other projects, I wanted to use additional status LED which needs more power. This is why I opted for separate power supply.

But the code works the same for v1 or v2 board.

Parts:

Some are generic parts that I have ordered a long time ago from eBay and since the listing has been removed.

Wemos D1 Mini ESP8266 module (clone)

RS-485 to TTL Converter Module

5.08mm Pitch Panel KF301-3P Screw Terminal Block PCB Connector

4 pin DC-DC buck converter power supply module (I used a different module, but that is no longer available)

WS2812 Neopixel module

If you need more information, I have a more detailed video on this project here: https://youtu.be/-V4L6XIhLb0