Using SSI module for absolute encoder in NR

Node-RED
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1

We are setting up a test setup to get acquainted with the 750-8213 running NR and MQTT.
We have most of the DI, DO, AO, AI modules working over the Kbus API by Jesse James Cox.
Now we want to use the 750-492 SSI module in combination with a digital absolute rotary encoder.
It seems this is not (yet) supported in the Kbus API.
Any ideas on how to build a workaround? Thx!

2

The best bet would be to switch away from the KBUS API to the “PFC Modbus Server”: GitHub - WAGO/pfc-modbus-server: Docker image containing Kbus Modbus server application "kbusmodbusserver" which acting like a Modbus-Coupler 750-352. It also acting as counter part for WAGO-IO-Check. The application "kbusmodbusserver" can be interessting for two reason: Direct access to KBus-IO-Modules for any third party process (Node-Red, Mono, Node.js, ...) who's able to send modbus requests.

This would essentially turn the IO bus into Mobus-based remote IO, with all the same address properties of something like a 750-362 coupler. The manual can be found here: WAGO Global | 1359074

It is certainly less user-friendly than the KBUS API. There are plans to expand the API, but not in the immediate future due to other high-priority projects.

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3

Hey Tyrone,

We got the modbus server running it shows the SSI modules as Analog inputs. The other analog inputs are returning data but the SSI stays 0.
This is how the modbus sees them:
Pos:13: Type: 750-630 / 0-0 BitOffsetOut:0; BitSizeOut:0; BitOffsetIn:0; BitSizeIn:32; Channels:2; PiFormat:1;
Pos:14: Type: 750-630 / 0-0 BitOffsetOut:0; BitSizeOut:0; BitOffsetIn:32; BitSizeIn:32; Channels:2; PiFormat:1;
Pos:15: Type: 750-630 / 0-0 BitOffsetOut:0; BitSizeOut:0; BitOffsetIn:64; BitSizeIn:32; Channels:2; PiFormat:1;

The only difference is the PiFormat:1 instead of 0.

Do you have any ideas what we could try to get data from the SSI?

4

I would suggest that you confirm that the process image is transmitting data using Codesys and to ensure that the wiring and device are transmitting properly.

Please see page 23 to check SSI compatibility.