ModbusBridge

Overview

ModbusBridge (mbridge) is a simple cross-platform (Windows, Linux) Modbus converter application that provides interconvertion between different types of Modbus protocol: TCP, RTU, ASC.

It can be used, for instance, in Raspberry Pi computer to act as Modbus converter.

It's free and open source software based on ModbusLib project:

https://github.com/serhmarch/ModbusLib

Application implements such Modbus functions as:

• 1 (0x01) - READ_COILS
• 2 (0x02) - READ_DISCRETE_INPUTS
• 3 (0x03) - READ_HOLDING_REGISTERS
• 4 (0x04) - READ_INPUT_REGISTERS
• 5 (0x05) - WRITE_SINGLE_COIL
• 6 (0x06) - WRITE_SINGLE_REGISTER
• 7 (0x07) - READ_EXCEPTION_STATUS
• 8 (0x08) - DIAGNOSTICS
• 11 (0x0B) - GET_COMM_EVENT_COUNTER
• 12 (0x0C) - GET_COMM_EVENT_LOG
• 15 (0x0F) - WRITE_MULTIPLE_COILS
• 16 (0x10) - WRITE_MULTIPLE_REGISTERS
• 17 (0x11) - REPORT_SERVER_ID
• 22 (0x16) - MASK_WRITE_REGISTER
• 23 (0x17) - READ_WRITE_MULTIPLE_REGISTERS
• 24 (0x18) - READ_FIFO_QUEUE

Using mbridge

To show list of available parameters print:

$ mbridge -?
Usage: mbridge -ctype <type> [-coptions] -stype <type> [-soptions]

Options (-c client, -s server):
  --version (-v) - show program version.
  --help (-?)    - show this help.
  -c<param>      - param for client.
  -s<param>      - param for server.

Params <param> for client (-c) and server (-s):
  * type (t) <type> - protocol type. Can be TCP, RTU or ASC (mandatory)
  * host (h) <host> - remote TCP host name (localhost is default)
  * port (p) <port> - remote TCP port (502 is default)
  * tm <timeout>    - timeout for TCP (millisec, default is 3000)
  * maxconn <count> - max active TCP connections (default is 10)
  * serial (sl)     - serial port name for RTU and ASC
  * baud (b)        - baud rate (for RTU and ASC) (default is 9600)
  * data (d)        - data bits (5-8, for RTU and ASC, default is 8)
  * parity          - parity: E (even), O (odd), N (none) (default is none)
  * stop (s)        - stop bits: 1, 1.5, 2 (default is 1)
  * tfb <timeout>   - timeout first byte for RTU or ASC (millisec, default is 1000)
  * tib <timeout>   - timeout inter byte for RTU or ASC (millisec, default is 50)

Options for server:
  -sunit (-su) <list> - list of units for server to responde like '1,3,6-10,11,27'

Examples:
  mbridge -stype TCP -ctype RTU -cserial COM6
  mbridge -stype RTU -sserial /dev/ttyUSB0 -sbaud 19200 -ctype TCP -chost some.plc

Next example makes Modbus bridge with RTU client part and TCP server part works on TCP port 502:

> mbridge -stype TCP -smaxconn 5 -ctype RTU -cserial "COM6"
RTU:Client parameters:
----------------------
port   = COM6
baud   = 9600
data   = 8
parity = No
stop   = 1
flow   = No
tfb    = 1000
tib    = 50

TCP:Server parameters:
----------------------
port    = 502
timeout = 3000
maxconn = 5

mbridge starts ...
TCP:Server opened
New connection: 192.168.1.102:50392
192.168.1.102:50392 Rx: 00 05 00 00 00 06 03 03 00 00 00 05
RTU:Client opened
RTU:Client Tx: 03 03 00 00 00 05 84 2B
RTU:Client Rx: 03 03 0A 00 00 00 00 00 00 00 00 00 00 23 F4
192.168.1.102:50392 Tx: 00 05 00 00 00 0D 03 03 0A 00 00 00 00 00 00 00 00 00 00
...
192.168.1.102:50392 Rx: 00 08 00 00 00 06 03 03 00 00 00 05
RTU:Client Tx: 03 03 00 00 00 05 84 2B
RTU:Client Rx: 03 03 0A 00 00 00 00 00 00 00 00 00 00 23 F4
192.168.1.102:50392 Tx: 00 08 00 00 00 0D 03 03 0A 00 00 00 00 00 00 00 00 00 00
Close connection: 192.168.1.102:50392
mbridge stopped

Build using CMake

1. Build Tools

   Previously you need to install c++ compiler kit, git and cmake itself. Then set PATH env variable to find compliler, cmake, git etc.

2. Create project directory, move to it and clone repository:

   $ cd ~
   $ mkdir src
   $ cd src
   $ git clone --recursive https://github.com/serhmarch/ModbusBridge.git
   

3. Create and/or move to directory for build output, e.g. ~/bin/ModbusBridge:

   $ cd ~
   $ mkdir -p bin/ModbusBridge
   $ cd bin/ModbusBridge
   

4. Run cmake to generate project (make) files.

   $ cmake -S ~/src/ModbusBridge -B .
   

5. Make binaries (+ debug|release config):

   $ cmake --build .
   $ cmake --build . --config Debug
   $ cmake --build . --config Release
   

6. Resulting bin files is located in ./bin directory.