Can't get runnig RS-485 on jessie

  • Hello

    im stucking get running RS-485 on an blank raspian-jessie image, with all current updatedes.

    downloaded the and installed.
    /dev/extcomm/0/0 is present.
    but no data are coming out.....

    with der Uni Pi Open Source Image all is working fine, see:

    root@raspberrypi:~# mbpoll /dev/extcomm/0/0 -a 1:3  -1
    mbpoll 0.1-23 - FieldTalk(tm) Modbus(R) Master Simulator
    Copyright (c) 2015 epsilonRT, All rights reserved.
    This software is governed by the CeCILL license <>
    Protocol configuration: Modbus RTU
    Slave configuration...: address = [1,2,3]
                            start reference = 1, count = 1
    Communication.........: /dev/extcomm/0/0,      19200-8E1 
                            t/o 1.00 s, poll rate 1000 ms
    Data type.............: 16-bit register, output (holding) register table
    -- Polling slave 1...
    Read output (holding) register failed: Connection timed out
    -- Polling slave 2...
    Read output (holding) register failed: Connection timed out
    -- Polling slave 3...
    Read output (holding) register failed: Connection timed out

  • administrators

    @mauri The issue with the Neuron tcp servers creating the virtual PTY for the serial port is, that it is not possible to set baudrate and parity when opening the /dev/extcomm in the standard way so it has to be done via the Modbus Register - "Configuration of RS485 serial line".

    The UniPian includes the new and proper approach using kernel driver. We hope to provide proper package system to distirbute the driver and also the tcp modbus app but for now, its included only in the UniPian.

  • @tomas_hora is there a solution for a jessie installation now? We based out Software on jessie. Is there a way to get it running?

  • You can compile a kernel driver module for Neuron, which should work on Jessie. You can find the source code here:

    If you can provide us with the exact kernel version (run "uname -a" as root) we can even compile it for you, the process is relatively trivial.

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