Firmware that makes ESP32 function as a remote I/O device with Modbus-TCP + configuration interface

Based on the following libraries

Modbus: https://github.com/emelianov/modbus-esp8266
Wifi manager: https://github.com/tzapu/WiFiManager
Programmed with Arduino IDE. Tested on TIA Portal and Twincat3.

Usage:

• Put pin 15 as HIGH for 3 seconds to start Wifi AP mode.
• Connect to Access Point with SSID: "EvisLAB-ESP32", Key: 12345678
• Go to 192.168.4.1 on your preferred browser
• Select pinMode options by the dropdown list for each pin. "Unused" is the default option
• Write your preferred static IP and the Gateway.
• Board will restart instantly after saving and be ready to connect to any Modbus-TCP master(client).

Notes:

Modbus functions and addresses:

• Write coils FC-15: 0 - 39 (Siemens: 1 - 40)
  • connected to Digital Outputs
• Read inputs FC-02: 100 - 139 (Siemens: 10101 - 10140)
  • connected to Digital Inputs
• Write Holding Registers FC-16: 200 - 239 (Siemens: 40201 - 40240)
  • connected to Analog Output (DAC), PWM pins
• Read Input Registers FC-04: 300 - 339 (Siemens: 30301 - 30340)
  • connected to Analog Inputs
• Port: 502
• Device ID: 1

Signal parameters

• Analog Inputs:
  • Resolution 12 bit
• Analog Outputs (DCA):
  • Resolution 8 bit
• PWM:
  • Resolution 12 bit
  • Frequency 10kHz

Flashing methods

• Arduino IDE

• ESP flash tool

  • Load the binary file and set the offset as 0x10000 (default for ESP32)
  • While keeping the "boot" button pressed, plug the USB cable, choose the COM port and then press Start.
  • After flashing start, release the "boot" button.