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Conversion of array to string [message #1834301]

Fri, 06 November 2020 16:46

Pradeep Patel

Messages: 16
Registered: October 2020

Junior Member

I have created my own SIFB which reads data from I2C port and store data bytes in output array. I want to transfer these data bytes to program executing on PC using MQTT protocol. For using MQTT protocol I want to convert data stored in array to string. Please suggest.

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Re: Conversion of array to string [message #1834315 is a reply to message #1834301]

Sat, 07 November 2020 05:49

zhao xiaolong

Messages: 5
Registered: November 2020

Junior Member

Hello，Pradeep. I saw your other post in the forum, which was about the raspberry PI lighting experiment. I'm also experimenting with raspberry PI, and I've used Python to call the I2C interface. So I want to ask how to call the I2C interface with 4diac. Looking forward to your reply. Thank you very much.

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Re: Conversion of array to string [message #1834320 is a reply to message #1834315]

Sat, 07 November 2020 07:40

Pradeep Patel

Messages: 16
Registered: October 2020

Junior Member

Hello Zhao, I did following:
1. Created my own SIFB as per documentation on 4Diac website. This SIFB should have event inputs like INIT and REQ. Exported this SIFB from 4Diac IDE to have .cpp file.
2. This exported .cpp file will have function "void FORTE_SIFBName::executeEvent(int pa_nEIID)". In this function under "scm_nEventINITID" you can write your code to initialize I2C port. Since it is .cpp file it will not support python and you need to convert your code to equivalent C or C++ code. I used linux calls like IOCTL and Open() functions to initialize I2C port of raspberry PI as raspbian is linux based.
3. In same function under "scm_nEventREQID" you can write read()/write() logic to send command and receive response from I2C device.
4. You need to include these files to forte source code and rebuild your forte for raspberry PI.
5. Write your 4Diac program using your SIFB to access I2C device and test

Hope this helps!

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Re: Conversion of array to string [message #1834324 is a reply to message #1834320]

Sat, 07 November 2020 09:08

zhao xiaolong

Messages: 5
Registered: November 2020

Junior Member

Thank you very much for your reply, which is very helpful to me. I will try to edit FB in this way. I never thought about modifying the.cpp file. It was awesome.

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Re: Conversion of array to string [message #1834404 is a reply to message #1834324]

Mon, 09 November 2020 19:30

Alois Zoitl

Messages: 1213
Registered: January 2014

Senior Member

Hi,

regarding your original question. What data type does your I2C reading FB have? If it is an IEC 61131-3 array. You could write yourself a simple FB and in that us ST to convert each individual element of your array to a string and append it to your full string. For that you can use the IEC 61131-3 conversion and string manipulation functions. All FBs in the IEC 61131-3 lib starting with an F_ are also available as function in algorithm with out the F_ prefix (e.,g F_BOOL_STRING -> var := BOOL_TO_STRING(xx);).

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