How to connect Sir88 to mesa board and linuxcnc

Dear specialists,

I hope to retrofit old biesse cnc machine using mesa boards.

It has broken PC.
Situation very common:
- 3 servomotors with analog comand inputs
- encoder inputs (not sure what voltage)
- many field mechanisms.

My question is about input/output modules that drives field mechanisms:
-8 modules of CNI Sir88 that conected through RS485 interface.
Two of them are in cabinet (relay output), others are installed in machine automation.
I don't have any documentation to this modules nor I don't know what interface is used to communication (supposedly ModBus). But my task is: to connect this modules to linuxcnc, all other tasks should do mesa boards.

Can any body help my with this?

Realy found answer for my question. If that modules are using Modbus, that I can connect with help of Ladder Logic.
I will study this in more detail.

But how to connect PC to modbus and to configure Port in phisical dimension (where to connect wires)?

what servo motors are connected to the driver
can you give us a plate image

modbus drives are som hard to get going
not many posts here on that
we most use cheep analog servos that fit the standard boards for 200USD

>>CACR-SR05BE
Currently I don't have question to Servodrives.
They are old ones that have +/- (2V to 10V) speed reference input.
and encoder outputs to CNC-board.

I have no experiance with ModBus. And it's realy crussial issue.

The biggest problem I foresee is, as far as I know Modbus connections In Linuxcnc are in userspace and are not realtime. This works ok for some things such as controlling a spindle's VFD, or a tool changer, but maybe not so well for something else, like a home or limit switches or controlling a servo.

Thank you Todd and Andypugh,

As Mesa board has it's own Inputs/Outputs, RealTime switches I'll connect directly to it.

But using that modbus modules that are installed is realy makes job easier, moreover, a lot of signals are at machine side, not in Cabinet.

As I said, I have no experiance with modbus, I was wrong a little.
I made automation on PLC S7-1200 (Siemens) and Modbus connections to spindles. I know what it is, and what problems I could have.

But linuxcnc has it's own development (that I don't know complitly) and how to work with that modbus I don't know currently.

But now, I make such main desicion:
Linuxcnc supports Modbus, and I can rely on it in my retrofit complitly.

I've get unswer about this I/O boards.

All their boards use FieldBus.
Does linuxcnc supports filedbus?

Don't know what "FieldBus" is.
According to Wikipedia it is a general term and could refer to one of many different protocols, one of which is Modbus.

andypugh wrote:

Todd wrote:

as far as I know Modbus connections In Linuxcnc are in userspace and are not realtime.

I think that Classic Ladder Modbus is Realtime (I have never used it) but probably only if connected via a serial port rather than USB-to-Modbus.

The more I think about it, I don't think it is realtime. That is why, in order to use Modbus with ClassicLadder you have to have to have the user-space part of it (the GUI) active for Modbus to work.
linuxcnc.org/docs/html/ladder/classic-ladder.html#_modbus