Virtual Modbus Slave and Node-Red

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RobD
Posts: 3
Joined: 12 Jun 2021, 09:11

Virtual Modbus Slave and Node-Red

Post by RobD »

Hi, I read a post indicating that nodes for Node-Red where being developed to allow access to the virtual Modbus slave module's registers from Node-Red. I have not been able to find any such nodes and was wondering if this work was ever completed or is there an existing method for communicating with the virtual slave module?

Kind regards,
Rob
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dirk
KUNBUS
Posts: 2005
Joined: 15 Dec 2016, 13:19

Re: Virtual Modbus Slave and Node-Red

Post by dirk »

Hi Rob, I took the liberty of moving your post here. This is where the experts who developed these nodes moderate.
In general, however, you can always access values from the process image by using an "exec" node.
You can then execute e.g.: "piTest -1 -q -r MyVariable" to get the value of MyVariable.
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nicolaiB
KUNBUS
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Joined: 21 Jun 2018, 10:33
Location: Berlin
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Re: Virtual Modbus Slave and Node-Red

Post by nicolaiB »

Hi Rob,

this should be possible. How does your current configuration (modbus in pictory, nodered) look like?

Nicolai
RobD
Posts: 3
Joined: 12 Jun 2021, 09:11

Re: Virtual Modbus Slave and Node-Red

Post by RobD »

Hi Nicolai,

I have opted for using the Modbus Server node from node-red-contrib-modbus instead of the virtual Modbus slave in Pictory. This has been working well so far.
I am currently writing data to about 70 registers and reading about 15 coils and I did not think invoking piTest was a very efficient way to do this.

Regards,
Rob
mitchellday06
Posts: 21
Joined: 29 Nov 2022, 00:08

Re: Virtual Modbus Slave and Node-Red

Post by mitchellday06 »

Hey i know this is some time ago, but when you say modbus are you meaning tcp of rtu? I am trying to work out the best method of connecting to a series of modbus rtu devices through node-red-contrib-modbus
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