From lechacal
Jump to: navigation, search
IMG 1979 small.png

For the previous version of MODWRT see here ModWRT.

Modbus RTU to Emoncms Influxdb Thingspeak

Modbus to Emoncms. The ModWRT is a Modbus RTU unit to interface with one or several RS485 RTU devices. The ModWRT sends a predefined set of registers value to a server for data logging and display.
The end server can be either of type Emoncms, Influxdb or Thingspeak.

All communication and dataflow parameters are configured using a web interface.

Technical Specifications

  • RS485 port for RTU
  • Ethernet port
  • Integrated Wifi
  • Micro-usb Power supply
  • Operating system: OpenWRT 15.05
  • Flash Memory: 16MB
  • PCB Dimensions: 55x40mm
  • Optional Wifi antenna


A complete MODWRT includes the base board and a SKW71 Module.

PCB Base Board

The base board can be purchased here.

IMG 1974 small.png

SKW71 Module

Skw71 pic01.jpg

The SKW71 module from Skylab runs the operating system OpenWrt.

  • Wifi enabled
  • Runs the ModWrt software
  • Collect acquired data from RTU's
  • Forward to Emoncms/Influxdb/Thingspeak

The SKW71 modules has two antenna options.

PCB Antenna

The antenna is internal and does not require any other parts. This usually a good option if other connecting devices are in a good range.

External Antenna

Link to the shop

If a stronger range is needed this can be a good option. Two additional components will be required.

  • 1 U.FL IPX to SMA cable.
  • 1 SMA Antenna.

The U.FL IPX connector fits on the SKW71 module.


IMG 1980 small.png

The Modwrt PCB fits in an aluminium enclosure with 40x64x30mm dimensions.

3D printed end plate are available.


The ModWRT web interface is build within the OpenWRT web interface.

There are three main functional area which are:
1/ RTU's definitions
2/ Servers definitions
3/ Dataflow configuration (ie which data goes where).

The web interface is briefly described below. See more details in the user manual.

1. RTU definition

All Modbus RTU devices can be configured on one single page using Slave ID and communication parameters (baud rate etc).

Web 001.png

2. Stream to Emoncms, Influxdb, Thingspeak definition

Internet of Thing (iot) servers can be configured on this page.

Modwrt streams 01.png

3. Dataflow Configuration

This page will configure all dataflow combination.

A single dataflow can query different RTU unit to send combined data onto a single export.

Modwrt dtfl 01.png

As an example the above example will display the following data on Emoncms.

Web 004.png

User Manual

Modwrt First use

Modwrt Web Interface

Modwrt on Command Line

Emonwrt3 Network Configuration (same applies for EMonwrt3 and Modwrt).

Modwrt Update New Software

Related Articles

Use PZEM-016 with MODWRT