Not Receiving Data from Request – Modbus

[bbailey]

Good day all!
I have RapidScada trying to connect to a RS-485 to Ethernet Converter via Modbus TCP (the original device has a port for Modbus RS-485 RTU but apparently it should work the same)

Right now I am getting:

2020-12-19 05:40:09 Establish a TCP connection with 172.16.15.150:42069

2020-12-19 05:40:09 Communication session with the Device 1 “ActualModbus”, type: KpModbus, address: 5, call number: 172.16.15.150
Request element group “Analog Levels”
Send (12): A0 C6 00 00 00 06 05 04 00 00 00 28
Receive (0/7):
Communication error!
Request element group “Analog Levels”
Send (12): A0 C7 00 00 00 06 05 04 00 00 00 28
Receive (0/7):
Communication error!
Request element group “Analog Levels”
Send (12): A0 C8 00 00 00 06 05 04 00 00 00 28
Receive (0/7):
Communication error!

2020-12-19 05:40:13 Disconnect from 172.16.15.150

The Device’s ModBus ID by default is 5 so I set the address to 5.
The IP address of my RapidSCADA server which I am testing it with is 172.16.15.154 and the converter’s local IP address is 172.16.15.150

I have a response from the Converter where it is saying it is receiving instructions from RapidSCADA but there is no transmission, as seen below:

https://imgur.com/m8wME8F WaveShare RS-485 Converter Web Page showing reception but no transmission

I have set the parameters in my RapidSCADA as ModBus TCP, Client Mode pointing to the remote IP and port of the converter.

RapidSCADA parameters:
https://imgur.com/WBeOlIT

Converter’s parameters:
https://imgur.com/OKm8bqW

My Line state has:
Line 1 “Simulated Line”
———————–
State : running
Action : 19/12/2020 06:05:25 Communication with Device 1 “ActualModbus”

Connection Channel
——————
Type: TcpClient
Connection: not established
Custom Parameters
—————–
TransMode = TCP

Common Properties
—————–
Modbus.Templates = Dictionary of 1 templates

Active Devices
————–
1. Device 1 “ActualModbus” : error

ALL HELP IS APPRECIATED

I have two theories:

EITHER the ModBus terminals are not communicating

OR

Something is wrong with the configuration.

Appreciate in advance

• This topic was modified 3 years, 4 months ago by Mikhail.

[bbailey]

LINK FOR PICS ABOVE (if not available)

[manjey73]

Does your converter convert the protocol from Modbus TCP to Modnus RTU ? or is it just an ethernet – rs485 interface converter ? If the latter, then set the transemode RTU mode and remove the callnumber leave only the IP and port communication line settings

[manjey73]

You have a simple interface converter, not a protocol converter. You configure the communication line as a TCP Client by specifying the IP and port. Scada is configured to work with the RS485 interface. transmode = RTU Address = 5 do not specify a Call Number, leave the field blank

• This reply was modified 3 years, 4 months ago by manjey73.

[bbailey]

Hello @manjey73 , thanks for the reply!

OK I have done all the changes you recommended and still having errors (but we are on the right path)

Here is the line log:
2020-12-19 11:14:57 Establish a TCP connection with 172.16.15.150:502

2020-12-19 11:14:57 Communication session with the Device 1 “ActualModbus”, type: KpModbus, address: 5
Request element group “Analog Levels”
Send (8): 05 04 00 00 00 28 F1 90
Receive (0/5):
Communication error!
Request element group “Analog Levels”
Send (8): 05 04 00 00 00 28 F1 90
Receive (0/5):
Communication error!
Request element group “Analog Levels”
Send (8): 05 04 00 00 00 28 F1 90
Receive (0/5):
Communication error!

2020-12-19 11:15:00 Disconnect from 172.16.15.150

2020-12-19 11:15:00 Establish a TCP connection with 172.16.15.150:502

2020-12-19 11:15:00 Communication session with the Device 1 “ActualModbus”, type: KpModbus, address: 5
Request element group “Analog Levels”
Send (8): 05 04 00 00 00 28 F1 90
Receive (0/5):
Communication error!
Request element group “Analog Levels”
Send (8): 05 04 00 00 00 28 F1 90
Receive (0/5):
Communication error!
Request element group “Analog Levels”
Send (8): 05 04 00 00 00 28 F1 90
Receive (0/5):
Communication error!

2020-12-19 11:15:04 Disconnect from 172.16.15.150

AND here is are Configuration settings as per recommendation.

The line state is giving this result:
Line 1 “Actual Line”
——————–
State : running
Action : 19/12/2020 11:18:46 Communication with Device 1 “ActualModbus”

Connection Channel
——————
Type: TcpClient
Connection: not established
Custom Parameters
—————–
TransMode = RTU

Common Properties
—————–
Modbus.Templates = Dictionary of 1 templates

Active Devices
————–
1. Device 1 “ActualModbus” : error

It looks much closer to what it should be reading as seen in this link

Looking forward to your response!

[Mikhail]

Hello,

According to the log file, you can connect to the converter, but there is no response from the device.
Check the following:
1. The device ID is correct (is set to 5).
2. RS-485 wires are correct. Try swapping A and B wires.

[manjey73]

Why are you using port 502 ? after all, by default, the device Ethernet-RS485 has port 23 when it is configured as a tcp server ?

[manjey73]

[manjey73]

Try reading just one register first and make sure they are readable. and only then add registers to the query group

[bbailey]

Hello @manjey73
Changed the Remote Port to 502, because in the tutorial had Port 502 and my team entered it to see if it would make a difference (it did not sadly). Changed it to Port 23 and no difference.

I changed the test to look at only one register (Battery Level, as seen in the request frame example given by the manufacturer
.

I am getting the following result, which matches the above:
2020-12-20 08:30:44 Establish a TCP connection with 172.16.15.150:23

2020-12-20 08:30:44 Communication session with the Device 1 “ActualModbus”, type: KpModbus, address: 5
Request element group “Battery Level Level Test”
Send (8): 05 04 00 19 00 01 E1 89
Receive (0/5):
Communication error!
Request element group “Battery Level Level Test”
Send (8): 05 04 00 19 00 01 E1 89
Receive (0/5):
Communication error!
Request element group “Battery Level Level Test”
Send (8): 05 04 00 19 00 01 E1 89
Receive (0/5):
Communication error!

2020-12-20 08:30:48 Disconnect from 172.16.15.150

I feel it is either the request is somehow incorrect and thus does not get the a response from the slave.

OR

The RS-485 itself is not working as there is no transmission.

In your expertise what do you think is the best solution?

[NOTE: I am not using a shielded twisted pair, but rather three normal (slightly large) power wires to run the short distance of 6 inches during tests. Do you think this will affect its performance?]

[bbailey]

Greetings @Mikhail, thanks for the response!

The Device ID by default is 5 and so that is my Dev Address in RapidSCADA, along with no call number as recommended for RTU slave devices using this Ethernet-to-RS485 converter.

Regarding the wires used for the RS-485, I am currently using:

three normal (slightly large) power wires to run the short distance of 6 inches during tests. Do you think this will affect its performance?

and not twisted pair as I am in testing. With the terminals: A, B, COM.

Do you think this would cause a problem in communication?

All help is appreciated!

[kumajaya]

Usually I use a Modbus tester application to confirm Modbus RTU/TCP communication. You can try https://store.chipkin.com/products/tools/cas-modbus-scanner or https://github.com/ed-chemnitz/qmodbus

[manjey73]

Have you tried connecting to the device via USB-RS485 ?

[bbailey]

No as to get it to the country I am in, especially during Christmas time, the package would take take more than a week to two weeks.

My work needs this to work asap, so lots of pressure haha.

But do you think improper cables are to blame?
(Greetings from Jamaica)

[Mikhail]

Do you think this would cause a problem in communication?

It is highly possible. If I were you, I would connect another converter instead of PLC and check if data are received from the 1st converter.

If your converter has more than 1 RS-485 port, you can perform this test using the single converter.

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