modbus-tk and python3

[Yuriy Vlasenko]

Hi everybody,

I use modbus-tk in a python2 project and all is good. Now I want to migrate to python3 (PyQt and Qt5 and so on). How can I use modbus-tk in python3 project?

Regards,

Yury

[Luc JEAN]

Hello Yuri,

Python 3 support is in progress. You can try the last commit. If you do it, please let me know if it is ok for you.

Best

luc

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[Yuriy Vlasenko]

Hi luc,

Thanks for an answer. I do need modbus library to python3, so I'm ready to try the steps you'll show.

Python 3 support is in progress. You can try the last commit. If you do it, please let me know if it is ok for you.

What is the last commit? I try modbus_tk 0.4.3 - is it right? 

And what is a way of trying? I installed modbus_tk with python3:

sudo python3 setup.py install

There were errors during the installation, so I attach 2 files with screenshots. On the 2-nd screenshot there is a test import, it shows OK. So I decided to continue.

But my project refused to work with the library - cannot import mobdus_tk.

Maybe you can see an error in my proceedings already? Please specify, I'm ready to co-operate.

Not seeing your answer I tried to include all your package in my project and to transform it to puthon3. But it is not so easy :)

BTW I found a puzzling thing in the modbus.py module: the var starting_addressW_FC23 (in an execute() function). It is not defined anywhere, AFAIK.

Best regards,
Yury

[Luc Jean]

Hi Yuri

Thanks for your help.

You should try the last commit of the github repository

https://github.com/ljean/modbus-tk

I've tried to start to support Python 3

Best

luc

[Yuriy Vlasenko]

luc,

I need a little bit of guidance. 

 

You should try the last commit of the github repository

https://github.com/ljean/modbus-tk

1) I've made:

sudo git clone https://github.com/ljean/modbus-tk

2) Next? 

I mean - where are those 281 files and how should I install them (sudo python3 setup.py install will take not the last commit?)

[Luc JEAN]

Hi Yuri,

You can make a "sudo python3 setup.py develop" See http://stackoverflow.com/a/19048754/117092 for difference

Best

luc

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[Yuriy Vlasenko]

Hi luc,

Thanks for you help with GIT. I am a newbie in this field.

I've made as you said and managed to run my script somehow. But got an error (look screenshots: 1-st is traceback, then the last call (utils.py) and my module call (adc_io.py). I read about this error but with no success.

Regards,

Yury

[Luc JEAN]

Hello Yuri,

I've pushed a new version on the github repository. It should improve Python 3 support. I am able to run RTU and TCP, master and slave, with Python 2 and Python 3.

One of the "big change" is that data is managed as bytes now in Python 3 and not as string. It could have impact on hooks if you use this feature. There is a 'to_data' function in utils.py if you need to manage conversion between string and bytes.

I am interested to know if it works for you. It would be great if some other people can also make a test on this new version.

Best

luc

[Yuriy Vlasenko]

Hi luc

 

I've pushed a new version on the github repository

Does it mean that I have to repeat: these steps: "clone" and "python3 setup.py develop"? Is it possible that that error I've mentioned before is corrected now? 

Or have I to use to_data() somehow to correct the error myself?

Regards,

 Yuty

[Luc JEAN]

You should just have to make git pull and git checkout. It should update the code source. 

I don't have access to all your code so I can't say if all is going to work "out of the box" or if you will need to change a few things. I think if you have no hooks, everything should be ok.

Best

luc

[Yuriy Vlasenko]

Hi luc,

Success! Thank you very much for you help!

I repeated clone and  python3 setup.py develop and tested your library in my Python3 project. It works OK.

I'm not sure you are interested in details, but I attach a screenshot with the test commands and their results in PyCharm IDE.

My next step is GUI development with Qt Designer 5 and then I return to a full project. Maybe I'll have some new results in mobdbus_tk testing.

Best regards,

Yury

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[Luc JEAN]

Great :-)

Thanks for feedback.

Best

luc

[Yuriy Vlasenko]

Hi Luc,

I've proceeded with Qt5 just enough to return to MODBUS.

And in looped call of request-respond I have a problem now.

2016-01-04 17:41 GMT+02:00 Luc JEAN <luc....@gmail.com>:

I think if you have no hooks, everything should be ok.

Maybe I'll need to use hooks and logging to find a bug. 

Here is a problem as I see it: 

1) modbus Master sends a request to a Slave and the Slave responds instantly (all transactions are less then 40 ms in duration - oscilloscope says). So far so good...

2) But! But Modbus stack returns the result in 1502 ms after the begin of request. Where does it waste all this time?

The screenshot shows exactly 1502 ms (excuse that lot of my prints).

I try the prev version of my script - with your modbus_tk but under Python2 - no problems. So it is surely not a hardware problem.

Can you suggest the best way to find a bug? If no - OK, I'll search myself.

Regards,

Yury

[Yuriy Vlasenko]

Hi Luc,

As i wrote:

середа, 6 січня 2016 р. 12:02:05 UTC+2 користувач Yuriy Vlasenko написав:

2) But! But Modbus stack returns the result in 1502 ms after the begin of request. Where does it waste all this time?

The screenshot shows exactly 1502 ms (excuse that lot of my prints).

The only reason I've found is a 

time.sleep(self.get_timeout())

line in send() function in the modbus_rtu.py file. 

I commented the line and everything runs OK, so far. Can you comment it? 

Regards,

Yury

 

[Luc JEAN]

Hello Yuri,

Sorry for late answer. 

Can you please tell me exactly where is this 'the.sleep'? Do you use master or server?

This  timeout should correspond to the interframe delay. It depends of your baud rate but should only be a few milliseconds. Can you please check the value returned by get_timeout? It should be 

>>> 3.5 * calculate_rtu_inter_char(baud_rate)

For 9600 --> 0.0040104166666666665 seconds

I hope it helps

Best

luc

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[Yuriy Vlasenko]

Hello Luc!

I use PC as a Master. 

2016-01-22 11:29 GMT+02:00 Luc JEAN <luc....@gmail.com>:

Hello Yuri,

Can you please tell me exactly where is this 'the.sleep'?

I attached a screenshot of the problem place (selected in editor) in /modbus_tk/modbus_rtu.py file. After I commented line 128 - problem dissolved :) 

As you can see, I'd printed the time.time() before and after the time.sleep() call. And the result showed - unwanted delay lays here.

 

Can you please check the value returned by get_timeout? It should be 

>>> 3.5 * calculate_rtu_inter_char(baud_rate)

For 9600 --> 0.0040104166666666665 seconds

Sorry, I cannot do it now. Another project is on my desk.

Regards,

Yury

[Yuriy Vlasenko]

Sorry! Attachment :)

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[Luc JEAN]

Hi Yuri,

Sorry for late answer. I didn't have time to look at this yet. Could you please enter an issue on the githup page to follow this problem?

Best

luc

[Yuriy Vlasenko]

Hi Luc,

You write:

Could you please enter year after githup on the page to follow this problem?

I do not know exactly what I have to do now. Please tell me.

Regrds,

Yury

[Luc JEAN]

Yuri,

Can you please enter an issue with as much details as possible for the timing issue you have on Python 3 : https://github.com/ljean/modbus-tk/issues?

Thanks

Best

luc

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