ModBusWiFi + ESP8266 connection guide
Connect a phone to Modbus RTU or Modbus ASCII devices through WiFi using an ESP8266 module with esp-link, a UART/RS485 converter, and a simple TCP serial bridge.
Connection Scheme
ModBusWiFi
esp-link
Required parts
- ESP8266-07 with 512 KB Flash or ESP8266-12 with 4 MB Flash.
- USB-UART adapter for flashing.
- TTL-RS485 converter for RS485 Modbus devices.
- Android phone with ModBusWiFi installed.
RS485 wiring
RS+ -> A / T/R+ RS- -> B / T/R-
Public sources
Firmware and tools are provided by their respective authors. Use the official links above first. Local copies are kept only as an authorized fallback.
Flash ESP8266
ESP8266-12, 4 MB Flash
0x00000 boot_v1.5.bin 0x01000 user1.bin 0x3FE000 blank.bin
Primary source: esp-link v2.2.3 release and NodeMCU Flasher.
ESP8266-07, 512 KB Flash
0x00000 boot_v1.5.bin 0x01000 user1.bin 0x7E000 blank.bin
Primary source: esp-link v2.2.3 release and NodeMCU Flasher.
Flash mode
Before flashing, put ESP8266 into programming mode. GPIO0 must be LOW during reset. Many NodeMCU boards handle this automatically.
Configure ModBusWiFi
Network address
Open Settings in ModBusWiFi and enter the ESP8266 address in IP:PORT format.
192.168.1.50:23
Serial parameters
Baud rate: 9600 Data bits: 8 Parity: None Stop bits: 1 Flow control: None
Mode
Select RTU or ASCII in ModBusWiFi according to the connected device settings. Device ID must match the Modbus address configured in the device.
PC Connection Option
If a Windows program can work only through a COM port, use a virtual COM utility from its official source. HW VSP3 maps a local COM port to the ESP8266 TCP address.
PC software -> Virtual COM -> TCP/IP -> ESP8266 -> UART/RS485 -> Modbus device
Command Examples
HCA inverter, RTU
01 06 20 00 00 02 03 CB RUN FWD 01 06 20 00 00 01 43 CA STOP 01 06 20 00 00 06 02 08 RUN REV
HCA inverter, ASCII
:0106006500058F frequency source RS485 :01060076000083 enable changes :01060076000182 disable changes :010620010C804C set 320.0 Hz
XY6020, RTU
01 03 00 00 00 01 84 0A set voltage 01 03 00 01 00 01 D5 CA set current 01 06 00 12 00 01 E8 0F output ON 01 06 00 12 00 00 29 CF output OFF
Troubleshooting
No response
Check WiFi network, ESP8266 IP address, TCP port, Device ID, and RTU/ASCII mode.
RS485 issue
Swap A/B wires if the bus is silent. Many adapters mark A/B differently.
Wrong values
Verify register address, scaling, byte order and whether the device expects decimal or HEX parameter addressing.
Official Sources
Third-party tools and firmware are provided by their respective authors. This page links to the original sources whenever possible.
Fallback Downloads
These local backup copies are available only to signed-in users, in case the original sources are temporarily unavailable. Please prefer the official sources above when they are online.
Fallback downloads are hidden for anonymous visitors. Sign in to access backup copies.