# Modbus Slave device PI

**URL:** <https://discourse.nodered.org/t/modbus-slave-device-pi/12483>\
**Category:** General\
**Created:** [22 June 2019 10:22 UTC](https://discourse.nodered.org/t/modbus-slave-device-pi/12483 "2019-06-22T10:22:45Z")\
**Posts on this page:** 14\
**Page:** 1

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**Author:** ![fordarn](https://avatars.discourse-cdn.com/v4/letter/f/49beb7/32.png) [@fordarn](https://discourse.nodered.org/u/fordarn)\
**Post date:** [22 June 2019 10:22 UTC](https://discourse.nodered.org/t/modbus-slave-device-pi/12483/1 "2019-06-22T10:22:45Z")

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Hi All  
Just wondering if anyone has came across a node set for the PI to act as a Modbus slave? All the Modbus nodes I have came across seem to be Master type arrangements

Thanks

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**Author:** ![bligher](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/bligher/32/10643_2.png) [@bligher](https://discourse.nodered.org/u/bligher)\
**Post date:** [4 August 2019 09:10 UTC](https://discourse.nodered.org/t/modbus-slave-device-pi/12483/2 "2019-08-04T09:10:12Z")

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Does anyone know anything? I'm also looking for Modbus Slave.

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**Author:** ![Colin](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/colin/32/17040_2.png) [@Colin](https://discourse.nodered.org/u/Colin)\
**Post date:** [4 August 2019 10:27 UTC](https://discourse.nodered.org/t/modbus-slave-device-pi/12483/3 "2019-08-04T10:27:15Z")

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This node says it contains a server node (the slave is a server). Whether it works I don't know.

> **[node-red-contrib-modbus](https://flows.nodered.org/node/node-red-contrib-modbus)**
>
> The all in one Modbus TCP and Serial contribution package for Node-RED.

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**Author:** ![bligher](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/bligher/32/10643_2.png) [@bligher](https://discourse.nodered.org/u/bligher)\
**Post date:** [4 August 2019 12:27 UTC](https://discourse.nodered.org/t/modbus-slave-device-pi/12483/4 "2019-08-04T12:27:57Z")

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Thanks for your answer, but i need Modbus RTU Slave.

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**Author:** ![Steve-Mcl](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/steve-mcl/32/4826_2.png) [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)\
**Post date:** [4 August 2019 12:32 UTC](https://discourse.nodered.org/t/modbus-slave-device-pi/12483/5 "2019-08-04T12:32:39Z")

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It says RTU in the description...

## The all in one Modbus TCP and Serial contribution package for Node-RED.

[![nodemodbus64](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/2X/4/41faeaf6b0e4be0aceba6cc34dd2fd3670ca4046.png)](https://www.npmjs.com/package/node-red-contrib-modbus)

[Node-RED](https://nodered.org/) contribution package for [Modbus](http://www.modbus.org/)

Based on [modbus-serial](https://www.npmjs.com/package/modbus-serial) with TCP, C701, Telnet, Serial, RTU buffered, and ASCII

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**Author:** ![Colin](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/colin/32/17040_2.png) [@Colin](https://discourse.nodered.org/u/Colin)\
**Post date:** [4 August 2019 12:34 UTC](https://discourse.nodered.org/t/modbus-slave-device-pi/12483/6 "2019-08-04T12:34:10Z")

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> [@bligher](#):
>
> but i need Modbus RTU Slave.

The server _is_ a slave.

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**Author:** ![bligher](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/bligher/32/10643_2.png) [@bligher](https://discourse.nodered.org/u/bligher)\
**Post date:** [5 August 2019 09:10 UTC](https://discourse.nodered.org/t/modbus-slave-device-pi/12483/7 "2019-08-05T09:10:56Z")

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Yes, but it is Modbus TCP/IP and i need Modbus RTU Serial.

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**Author:** ![Colin](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/colin/32/17040_2.png) [@Colin](https://discourse.nodered.org/u/Colin)\
**Post date:** [5 August 2019 09:59 UTC](https://discourse.nodered.org/t/modbus-slave-device-pi/12483/8 "2019-08-05T09:59:19Z")

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> [@bligher](#):
>
> i need Modbus RTU Serial.

The node description says  
" Based on modbus-serial with TCP, C701, Telnet, Serial, RTU buffered, and ASCII"  
Are you saying that it does not do what it says?

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**Author:** ![Petr](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/petr/32/6413_2.png) [@Petr](https://discourse.nodered.org/u/Petr)\
**Post date:** [5 August 2019 12:27 UTC](https://discourse.nodered.org/t/modbus-slave-device-pi/12483/9 "2019-08-05T12:27:13Z")

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I am reading my RS485 Modbus RTU devices using Python + USB RS485 converter on Raspberry pi. Than sending mqtt messages to the broker. Works great.

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**Author:** ![Colin](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/colin/32/17040_2.png) [@Colin](https://discourse.nodered.org/u/Colin)\
**Post date:** [5 August 2019 12:30 UTC](https://discourse.nodered.org/t/modbus-slave-device-pi/12483/10 "2019-08-05T12:30:20Z")

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@bligher is wanting to simulate a modbus slave using node-red, not communicate with modbus devices.

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**Author:** ![Petr](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/petr/32/6413_2.png) [@Petr](https://discourse.nodered.org/u/Petr)\
**Post date:** [5 August 2019 12:38 UTC](https://discourse.nodered.org/t/modbus-slave-device-pi/12483/11 "2019-08-05T12:38:12Z")

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I see. Sorry for misunderstanding.

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**Author:** ![bligher](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/bligher/32/10643_2.png) [@bligher](https://discourse.nodered.org/u/bligher)\
**Post date:** [5 August 2019 12:51 UTC](https://discourse.nodered.org/t/modbus-slave-device-pi/12483/12 "2019-08-05T12:51:54Z")

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My PLC (Master) is connected over RS485 USB to RPI (Slave). I tried to use the "The all in one Modbus TCP and Serial contribution package" and it didn't work. I opened a issue to get a hint at [github](https://github.com/biancode/node-red-contrib-modbus/issues/150).

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**Author:** ![Petr](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/petr/32/6413_2.png) [@Petr](https://discourse.nodered.org/u/Petr)\
**Post date:** [5 August 2019 13:07 UTC](https://discourse.nodered.org/t/modbus-slave-device-pi/12483/13 "2019-08-05T13:07:23Z")

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What about RPI acting as a RS485 slave using Python?

> **[Modbus slave in Python - Jonathan Daniel](https://jonathandaniel.website/modbus-slave-in-python-raspberry-pi-3/)**
>
> While working on the valve controller at Sensor-Sense, one of the customers requested to have support for Modbus to read out measurements from multiple devices. For this they were referring to RS-485 communication. Since the codebase was already...

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**Author:** ![FrankAB](https://avatars.discourse-cdn.com/v4/letter/f/ee59a6/32.png) [@FrankAB](https://discourse.nodered.org/u/FrankAB)\
**Post date:** [19 June 2021 07:37 UTC](https://discourse.nodered.org/t/modbus-slave-device-pi/12483/14 "2021-06-19T07:37:51Z")

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It's been 2 years since this thread was founded.  
Has anyone found a solution how to read data via RS-485 from RPi set as a Slave?  
The links in the 2 entries above are not working.  
Greetings  
Franciszek