RevPi as a Modbus slave

[peterq]

Hi,

I am working on designing a control system around a revolution pi system and I need some help understanding the different base units.

I plan to use the revpi module as a slave device receiving commands by modbus over TCP and conducting specific sequences of digital I/O when given commands.

I would write a small program on the rev pi to watch the modbus registers and activate the DI/DO sequences.

I am trying to understand my requirements for the base module and want to check my thinking.

I think I should be able to do this with a Core SE base module. As far as I can tell the difference with the Core S is that I can't use the gateway modules which I don't think I need for this project. Then the difference between the Core and Connect as far as I can tell is that the Connect has additional ports and also full root access.

I am worried about not having "full root access" to my revpi - will I be unable to install packages with sudo if I do not have a connect? This seems strange!

Thanks for your advice

[dirk]

Hi peterq, welcome to the Revolution Pi community, check out this tutorial, it covers exactly what you have in mind:
Revolution Pi Gateway Tutorial

Further good sources of information can be found here in the form of video tutorials
Tutorial 22 – Modbus TCP Slave

[peterq]

Hi Dirk,

Thanks for the response! The tutorial seems clear to me - what I am unsure about is if I need a specific base unit to do this - do I need a connect or core, SE or S?

Would I be able to set up the Core SE as a modbus TCP slave?

Thanks,

Peter

[dirk]

Hi Peter, of course you need one of these modules
https://revolutionpi.com/shop/en/base-modules

[pi_admin]

Hi Dirk,

Thanks for the response! The tutorial seems clear to me - what I am unsure about is if I need a specific base unit to do this - do I need a connect or core, SE or S?

Would I be able to set up the Core SE as a modbus TCP slave?

Thanks,

Peter

Hi Peter,

sorry for the misunderstanding. All RevPi Base modules (incl. Core and Connect) have the same operating system and therefore all base modules have "full root rights".

The biggest difference between the Core S/SE and Connect S/SE versions is the hardware interface (for example, the RevPi Connect has a RS485 port, a second RJ45 port and so on).

So regarding your question if it is possible to use the RevPi Core SE as a Modbus TCP Slave: Yes you can.


Additional Note: The S/SE versions are based on the Raspberry Pi Compute Module 4S which is limited to 1GB of RAM. So if you need more RAM you have to switch to the Compute Module 4 which is available with up to 8 GB of RAM and are only built in our Connect - Series (our devics which are powered by the Compute Module 4 are called RevPi Connect 4) - >https://revolutionpi.com/shop/en/revpi-connect4

[peterq]

Hi both,

Thanks very much for the information - this is very helpful!