Modbus device not working with Labview, but works with Python.

[henk1000]

For this device with python I just request to read the register 0 and then I get back whatever is there. With labview I only get error. It connects but does not write neither read. I might be missing something very basic. By the way, I have been using Labview for 5 days till now, so I am sure the solution will come 😉.
On the windows firewall I allowed everything regarding labview, etc.

[henk1000 · Accepted solution]

I have found a quick/temporary solution for my problem. Now just need some implementation. Since the Python code was working well, I just call the script inside Labview and get my numbers.
Still bothered by Labview Modbus library not working but for the moment it's fine.

[K C]

Hi,

Like Stockhouse said the ModBus address issue can be really a problem. 

Does your device starts at address 0 or 1

In the VI you used a loop. A read every 200msec. Can you device handle this ?

And you should use the 'ModBus master out' (right top output) of the read VI

Kees

[henk1000]

Hi Kess,

With the python code, I just read the registers (e.g 60, 61) and I get the value I need in hexadecimal.
In Labview I have tried different numbers for the quantity and initial address, but it did not work. I will try different configurations to see how it works. I am quite new to Labview (Started last Friday 😊) so I suppose I still have to figure out plenty of stuffs. Thankfully the community here is quite active and supportive.

Regarding the scan time of my device, I am not sure if it can handle the 200 ms. I will try longer time and post here the results.

Best,

Henrique

[BertMcMahan]

Post your Python code as well, perhaps that will help us help you debug.

[henk1000]

Sure. Here is the python code for connecting to a modbus device.
"

from pymodbus.client import ModbusTcpClient

try:

    client = ModbusTcpClient('000.000.0.000', port=000)

    print("Modbus connected")

except ConnectionError as errorcom:

    print("Can not connect to PLC!")

    raise SystemExit from errorcom

v = client.read_holding_registers(60,13).registers

print(v)

client.close()

"

[henk1000]

I finally managed to connect to two other different devices with Labview !!! 😍
Still do not understand why two devices work with Labview (and python) and the other only with Python.