Error deploying Python Code to Raspberry Pi

Hi, I just wanted to test a simple program to test the functionality of running python in a simulink environment as shown in the model below.

with the function block containing the following code:

function out = RunPython(in1, in2)
    out = 0; % Has to be preassigned, otherwise Simulink throws an error
    coder.extrinsic('py.Python_ExampleCode.test') % Python functions have to be run extrinsically, meaning no C code generated
    out = py.Python_ExampleCode.test(in1, in2);
end

with the python code it is referencing being:

def test(in1,in2):
    out = in1+in2
    return out

And this works fine when run on the development computer, however when i try to deploy this onto a Raspberry Pi Zero W, the following error message comes up.

The extrinsic function 'py.Python_ExampleCode.test' is not available for standalone code generation. It must be eliminated for stand-alone code to be generated. It could not be eliminated because its outputs appear to influence the calling function. Fix this error by not using 'py.Python_ExampleCode.test' or by ensuring that its outputs are unused. Function 'MATLAB Function' (#25.245.271), line 4, column 11: "py.Python_ExampleCode.test"

Just wanted to know how this problem can be worked around or solved. Also note i have verified that the issue is not on the Pi end as I can deploy a simple LED blink test using the Simulink library for the Raspberry Pi

Answer 1

[Dinesh]

Hi Farhan,

I understand that you are trying to test a simple program to check the functionality of running Python in a Simulink environment. Also, that you can run it properly on your development computer, but you encounter issues when deploying it onto a Raspberry Pi.

The issue arises because when you are performing a simulation, 'coder.extrinsic' functions do not get compiled but are directly sent to MATLAB for execution. However, in the case of code generation, the process is a little bit different. If the output of an 'extrinsic' function affects the output of the calling function, it throws an error. Extrinsic functions for code generation can only be used for data analysis and data logging tasks.

Please refer to the following image, which represents the flow of function execution for extrinsic functions:

source(MATLAB documentation)

For more details regarding the extrinsic functions and using MATLAB engine to execute a function call please refer to the following MATLAB documentation.

• https://www.mathworks.com/help/simulink/ug/use-matlab-engine-to-execute-a-function-call-in-generated-code.html
• https://www.mathworks.com/help/simulink/slref/coder.extrinsic.html#mw_9ac08256-e7de-48a0-94a0-e16720bb087a

Hope this helps.

Best Regards,

Dinesh Reddy Gatla.