Using python to access T7-Pro over ethernet and reading AIN

4 posts / 0 new

Tue, 07/21/2015 - 17:54

miriya52

Hello,

I am trying to use python to read input or control output on a T7-Pro. I would like to access the T7-Pro over ethernet.

I tried the "list_all" but the no labjacks show up when my T7-Pro is only connected over ethernet. Currently, the T7-Pro is configured for DHCP, and I can ping the IP address (when I read the network configuration while connected over USB). However, when I tried reading AIN over TCP modbus with pymodbus, it doesn't detect the T7-Pro.

The next step is to configure the Labjack for static IP. Is there a python API for accessing the T7-Pro over ethernet, or is TCP modbus via pymodbus the only way?

Thanks,

Anna

Tue, 07/21/2015 - 18:45

LabJack Support

Start with the Ethernet

Start with the Ethernet Troubleshooting section towards the end of this page:

https://labjack.com/support/app-notes/basic-networking-troubleshooting

There are 8 steps there and usually 1 of them will point you towards your problem or help us solve your problem.

Wed, 07/22/2015 - 13:20

miriya52

Thanks, it seems that

Thanks, it seems that configuring the T7-Pro for static IP on our office network has made it possible to access via python TCP modbus from both Mac OS and BeagleBone Black Debian Linux.

Just a note that I think there is a bug in the "t7_test.py" example in this link: https://labjack.com/support/software/examples/modbus/python

$ python t7_test.py

Traceback (most recent call last):

File "t7_test.py", line 25, in <module>

rq = client.write_registers(55110,uint16_to_data(1234))

File "/usr/local/lib/python2.7/dist-packages/pymodbus/client/common.py", line 97, in write_registers

request = WriteMultipleRegistersRequest(address, values, **kwargs)

File "/usr/local/lib/python2.7/dist-packages/pymodbus/register_write_message.py", line 138, in __init__

self.count = len(self.values)

TypeError: object of type 'int' has no len()

When I comment out "rq = client.write_registers(55110,uint16_to_data(1234))", the script runs fine.

Thu, 07/23/2015 - 18:32

LabJack Support

Thanks for bringing that

Thanks for bringing that error to our attention. The example has been fixed, and now uses write_register instead of write_registers for that particular call since uint16_to_data returns a 1 register data value.