RevPi Connect SE Sensor Connection

[user123]

Hey RevPi Community,

I am currently using a RevPi Connect SE, which is connected via the RS485 serial port to a measurement sensor. I have verified the wire connection, and it appears to be correct. However, I am facing an issue where I am not receiving any sensor data. I followed the instructions for the Modbus-RTU Slave and created a Node-Red flow, but unfortunately, there is no debugging information available. Although it worked temporarily, I now encounter an access denied error when typing /dev/ttyRS485 in the command line.

Could someone assist me with this issue?

Thank you in advance!

[dirk]

Hello user123, ok so you have configured your connection like in video tutorial #21?
Take a look at the instructions in that post for debugging the status registers:
viewtopic.php?p=15497&hilit=modbus+rtu+status#p15497
What kind of sensor do you have and which serial parameters have to be set, i.e. baud rate, Modbus address, stop bits, parity?
Did the connection work once? If not, then a logic analyzer or an oscilloscope may be helpful to investigate the RS485 line.

[user123]

I’m working with a magnetic measurement sensor that slides along a metal band and displays its readings on an internal display. The communication setup i've configured is for Modbus RTU Slave Slave like this: https://kunbus-gmbh.atlassian.net/servi ... /416055479 . Here are the details:
baud rate: 9600, Modbus address: non, stop bits: 1, parity non
9600 Baud / 8 Databit / No parity / 1 Stopbit (9600/8/N/1)

The sensor data worked once, and after that, it didn’t show me any

[dirk]

Hi user123, can you say what might have changed since the Modbus communication stopped working?
Can you say what is in the status registers?
https://revolutionpi.com/en/tutorials/m ... rect=en-US

Here is a troubleshooting that is related to this you have to translate it but maybe it helps to jump into it quicker.
viewtopic.php?p=15524&hilit=modbus+stat ... ter#p15524

[user123]

Sorry for the late reply, i changed nothing, i dont know whats going on with this device, i also followed the instruction you have sent me but there is no change.

[dirk]

Hello user123, thank you for your patience, so do you still need support? If so, please send me an SOS-Report - here is how this works:
https://kunbus-gmbh.atlassian.net/servi ... 2036400208

[dirk]

Hello user123, Please try to use a build rate higher than 9600 to communicate with your sensor. There is a problem that occurs in connection with this build rate.
EDIT: No this issue is just related to setups that use I/O modules and the Bullseye image. According to the images you have provided your system is using a previous version.