How to disable and enable the 1Wire bus (M503)

rob

Hi,

I just ran into the same problem as Vesa (one wire bus suddenly lost) and I can confirm that this procedure worked, but I had to reboot the rpi afterwards.

I wonder if the change to /etc/systemd/system/neurontcp.service is really necessary, I initially tried polling the server without modifying the file and it seemed to work anyway.

If someone else needs this, the only cli tool to poll the modbus server I found functioning on the rpi is this one:
https://datapacket.dl.sourceforge.net/project/mblogic/MBLogic-All/MBLogic_All_Release-32/mblogic_all_2011-04-16.zip

You will have to set the line endings in the file to linux style, before running:
./pollmb.py -p 502 -u 1 -f 5 -a 1001 -q 1 -d 1
./pollmb.py -p 502 -u 1 -f 5 -a 1001 -q 1 -d 0

TomasKnot

@rob
It listens on 127.0.0.1 by default. The tool is written by us (you can find the source code at http://git.unipi.technology:3000/UniPi/neuron-modbus-tools, though note that not all of our software is opensourced) so I am quite confident it is necessary. It is of course not necessary if the client software is run locally via 127.0.0.1.

That said, the Linux libmodbus library did contain a bug where this setting was not applied correctly and ignored instead. Somewhat humorously I believe that the bug is still there in the version used on the main Debian repository (we statically link against a newer version of the modbus library instead, which does not have this issue), and as a result quite a few IoT devices likely unintentionally listen on all IPs.

(Incidentally this issue was uncovered by DavidCozens, to give proper credit)

Vesa Kauppinen

Hi @tomasknot

I'll come back to this topic again. Is it possible to do the same for Modbus in M503? I mean reset the bus (disable/enable)

Br,
Vesa

Martin Kudláček

Hello @vesa-kauppinen,
yes, check our Modbus Registers Maps: https://kb.unipi.technology/files:products:02-neuron

For M503 it is coil 1001 - Enable/Disable 1Wire Bus

Best regards,
Martin

Vesa Kauppinen

@martin-kudláček

Hi,

That's what we've done with 1-Wire and it works.

I mean, is it possible to do this same 'reset' for Modbus (RTU) itself? We sometimes lose a modbus device.

Br,
Vesa

Martin Kudláček

Oh, sorry for the misunderstanding @vesa-kauppinen.

We have a functionality called Master Watch Dog (MWD). When enabled, the underlying HW will watch when the last communication happend. If it will be longer than the preset time, it will reboot itself. Now, this can be set per group in the PLC, and it will watch if the ModbusTCP server communicates with the given group. If not, the board will reboot. Similarly, this can be set on the extensions as well. If nothing communicates with the extension over ModbusRTU, the extension reboots itself.

This can be set via modbus. Look for the "Enable MWD" coil and "MWD timeout" register. The timeout is in miliseconds.

Best regards,
Martin

Vesa Kauppinen

@martin-kudláček

Thank you!

Can you give a noob example of how to set 'MWD Enable' to 1 with pollmb.py?

Br,
Vesa

Martin Kudláček

@vesa-kauppinen

Sorry, I've never used the pollmb.py. Would be the mbpoll example sufficient? You can install the mbpoll from our repository: apt update && apt install mbpoll

Martin

Vesa Kauppinen

@martin-kudláček

Yes. If you can give mbpoll example that would be great!

:)

Br,
Vesa

Martin Kudláček

@vesa-kauppinen

For Group 1 on M503

Verify the status of the MWD (if 0 - MWD disable, if 1 - MWD enabled but never rebooted, if 2 - MWD enabled and already rebooted):
mbpoll -m tcp -a 0 127.0.0.1 -0 -1 -r 6

Set the MWD timeout to 5000ms:
mbpoll -m tcp -a 0 127.0.0.1 -0 -r 1008 5000

Enable the MWD:
mbpoll -m tcp -a 0 127.0.0.1 -0 -r 6 1

Write the settings to the NVRAM:
mbpoll -m tcp -a 0 127.0.0.1 -0 -t 0 -r 1003 1

Verify the MWD by stopping the UniPi Modbus TCP server:
sudo systemctl stop unipitcp

The both lines of LEDs should blink for 1sec after the MWD timeout

Disable the MWD:
mbpoll -m tcp -a 0 127.0.0.1 -0 -r 6 0

Write the settings to the NVRAM:
mbpoll -m tcp -a 0 127.0.0.1 -0 -t 0 -r 1003 1

For Group 2 on M503
Use the MWD control register 114 instead of 6
Use the MWD timeout register 1108 instead of 1008
Use the Save configuration coil 1103 instead of 1003

Vesa Kauppinen

@martin-kudláček

Thanks for the good instructions! After enabling MWD, setting timeout and writing the settings:

mbpoll -m tcp -a 0 127.0.0.1 -0 -1 -r 6
mbpoll 1.2-6 - FieldTalk(tm) Modbus(R) Master Simulator
Copyright (c) 2015 epsilonRT, All rights reserved.
This software is governed by the CeCILL license <http://www.cecill.info>

Protocol configuration: Modbus TCP
Slave configuration...: address = [0]
                        start reference = 6, count = 1
Communication.........: 127.0.0.1, port 502, t/o 1.00 s, poll rate 1000 ms
Data type.............: 16-bit register, output (holding) register table

-- Polling slave 0...
[6]:    3

...or...

mbpoll -m tcp -a 0 127.0.0.1 -0 -1 -r 114
mbpoll 1.2-6 - FieldTalk(tm) Modbus(R) Master Simulator
Copyright (c) 2015 epsilonRT, All rights reserved.
This software is governed by the CeCILL license <http://www.cecill.info>

Protocol configuration: Modbus TCP
Slave configuration...: address = [0]
                        start reference = 114, count = 1
Communication.........: 127.0.0.1, port 502, t/o 1.00 s, poll rate 1000 ms
Data type.............: 16-bit register, output (holding) register table

-- Polling slave 0...
[114]:  3

What does that result (3) mean? Its not 0, 1 or 2.

Btw

sudo systemctl stop unipitcp

should be

sudo systemctl stop neurontcp

in Neuron M503...right??

Br,
Vesa

Martin Kudláček

Hi @vesa-kauppinen,
sorry the value 3 is 1 + 2, which means board has MWD enabled and the MWD already rebooted the board.

The service is called unipitcp, but in older packages it was called neurontcp. The service is the same for Neurons and Axons, so we renamed it to unipitcp to make it more clear.

Best regards,
Martin

Vesa Kauppinen

@martin-kudláček

Aaaaa...of course :D

But what about this: either 11 or 3

root@residevice:~# mbpoll -m tcp -a 0 127.0.0.1 -0 -1 -r 6
mbpoll 1.2-6 - FieldTalk(tm) Modbus(R) Master Simulator
Copyright (c) 2015 epsilonRT, All rights reserved.
This software is governed by the CeCILL license <http://www.cecill.info>

Protocol configuration: Modbus TCP
Slave configuration...: address = [0]
                        start reference = 6, count = 1
Communication.........: 127.0.0.1, port 502, t/o 1.00 s, poll rate 1000 ms
Data type.............: 16-bit register, output (holding) register table

-- Polling slave 0...
[6]:    11

root@residevice:~# mbpoll -m tcp -a 0 127.0.0.1 -0 -1 -r 6
mbpoll 1.2-6 - FieldTalk(tm) Modbus(R) Master Simulator
Copyright (c) 2015 epsilonRT, All rights reserved.
This software is governed by the CeCILL license <http://www.cecill.info>

Protocol configuration: Modbus TCP
Slave configuration...: address = [0]
                        start reference = 6, count = 1
Communication.........: 127.0.0.1, port 502, t/o 1.00 s, poll rate 1000 ms
Data type.............: 16-bit register, output (holding) register table

-- Polling slave 0...
[6]:    3

root@residevice:~# mbpoll -m tcp -a 0 127.0.0.1 -0 -1 -r 6
mbpoll 1.2-6 - FieldTalk(tm) Modbus(R) Master Simulator
Copyright (c) 2015 epsilonRT, All rights reserved.
This software is governed by the CeCILL license <http://www.cecill.info>

Protocol configuration: Modbus TCP
Slave configuration...: address = [0]
                        start reference = 6, count = 1
Communication.........: 127.0.0.1, port 502, t/o 1.00 s, poll rate 1000 ms
Data type.............: 16-bit register, output (holding) register table

-- Polling slave 0...
[6]:    11

Br,
Vesa

Martin Kudláček

@vesa-kauppinen

Ok, this is a little bit tricky. The register has 16bits, and some of the bits represent some state or function.

Bit 0: Set or read the status of the MWD
Bit 1: The MWD rebooted the boarde
other bits contain some debug information, which we haven't documented yet

So value 11 in decimal is 0000 0000 0000 1011 in binary. The bit no. 0 (first from the right) is 1, which means MWD is enabled. The bit no. 1 (second from the right) is 1, which means MWD already rebooted the board. Other bits don't apply to you.

You can "mask" the lowest 2 bits with boolean operation AND, typically with bit mask in hexadecimal representation:

register_6 && 0x0003

Or with binary mask:

register_6 && 0b11

I hope this helps you.
Martin

Vesa Kauppinen

@martin-kudláček

Okay. This clarified the case :)

Thank you!

Br,
Vesa

Vesa Kauppinen

@martin-kudláček

Hi...again

One more stupid question: How do I reset 1-wire bus with mbpoll?

I mean, how can i "convert" those commands:

./pollmb.py -p 502 -u 1 -f 5 -a 1001 -q 1 -d 1
./pollmb.py -p 502 -u 1 -f 5 -a 1001 -q 1 -d 0

to mbpoll "format". I just don't understand how to read/write coils with mbpoll.

Thank you!
Vesa

Martin Kudláček

Hi @vesa-kauppinen,
writing 1 to coil 1001:

mbpoll -m tcp -a 0 127.0.0.1 -t 0 -0 -r 1001 1

Writing 0:

mbpoll -m tcp -a 0 127.0.0.1 -t 0 -0 -r 1001 0

You can learn more from the quite detailed help of the mbpoll:

mbpoll -h

Regards,
Martin