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Wireless Modbus-to-Modbus bridge

Wireless Modbus-to-Modbus bridge

Model number: WM-1
Frequency: ISM 868MHz (EU)
Dimensions: 93x45x27 mm


  • Replacement for RS485 wiring solution with wireless. Optimal for long range Modbus RTU serial communications with half duplex configuration.

Installation and mounting

  • :!: Carefully open WM-1 module and configure serial communication with jumpers. (Default configuration is 9600bps, 8N1 with normal timeout)
  • :!: Place WM-1 module at least 10cm from other objects. Installation is not recommended inside metal cabinets.
  • Connect RS485 terminals to WM-1 RS485 terminals
    • A - A
    • B - B
    • C - GND
  • Connect to 230V power supply
  • Bind modules to wireless network


  • replacement for RS485 wiring
  • Modbus RTU serial protocol
  • wired/wireless combinations
  • very long range, no hopping
  • protected private connection
  • multiple slaves per device
  • multiple addressable groups

Technical specification

Power supply: 230V, 50/60Hz, 1W
Ingress protection: IP20
Operating temperature: -20..50°C
Storage temperature: -40..85°C
Relative humidity: 0..85% n/c

Terminals and wiring

To power sensor A RS485 bus
To power supply L 230V AC

Serial configuration and timeout

  • Available baudrates 2400, 9600, 19200, 38400 bps
  • Data bits and parity 8N1, 7E1, 8E1, 8N2
  • :!: Max 64 bytes per transmition
  • Integrated 240 Ohm termination resistor

Wireless binding

Create new secure group

* turn on all devices at the same time
* within 10 seconds, while RF LED is blinking, press and hold button on one of the devices
* after a second, the new address is randomly generated and sent to all devices. RF LED will blink 3 times to confirm the new address.

Add new device to the group

* turn on the device
* within 10 seconds, press and hold button on one of the existing devices
* after a second, the existing group address is sent to the new device. RF LED will blink 3 times to confirm the address is sent.

Topology examples

* Modbus master, connected to 12 slaves using a pair of WM-1 devices
* Modbus master, connected to 10 slaves, organized in two groups
* Modbus master, connected to 5 slaves, each one having local WM-1 device

Multiple groups

* When the system has two or more separate Modbus lines, they should be configured as separate groups. 
* Each group has a single master and one or more slaves.
* Groups can't talk to each other, but they share the same bandwidth. 
* Two masters may start transmitting at the same time causing collisions. 
* To reduce number of missed messages, keep the traffic low.

Connection check

  • Press button shortly
  • RF LED will blink shortly on each connected device
  • Serial interface is unaffected

Factory reset

  • Hold button and turn the device ON
  • RF led will blink twice. Group address is now reset to default.
  • Other devices will not be affected.

wiki/20_rdc_charger/15_hardware/22_wm-1.txt · Last modified: 2023/05/26 13:04 by