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Editorial Team
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Asked: 2026-06-17T20:56:27+00:00

2nd UPDATE Almost there!! But getting a ValueError: Attempting to use a port that

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2nd UPDATE

Almost there!! But getting a “ValueError: Attempting to use a port that is not open”

File "c:\Python27\lib\site-packages\flask\app.py", line 1701, in __call__
return self.wsgi_app(environ, start_response)

File "c:\Python27\lib\site-packages\flask\app.py", line 1689, in wsgi_app
response = self.make_response(self.handle_exception(e))

File "c:\Python27\lib\site-packages\flask\app.py", line 1687, in wsgi_app
response = self.full_dispatch_request()

File "c:\Python27\lib\site-packages\flask\app.py", line 1360, in full_dispatch_request
rv = self.handle_user_exception(e)

File "c:\Python27\lib\site-packages\flask\app.py", line 1358, in full_dispatch_request
rv = self.dispatch_request()

File "c:\Python27\lib\site-packages\flask\app.py", line 1344, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)

File "G:\OverAir\arduino\server.py", line 19, in light_off
board.output([pin])

File "G:\OverAir\arduino\arduino.py", line 16, in output
self.__sendData(len(pinArray))

File "G:\OverAir\arduino\arduino.py", line 56, in __sendData
while(self.__getData()[0] != "w"):

File "G:\OverAir\arduino\arduino.py", line 61, in __getData
return self.serial.readline().rstrip('\n')

File "c:\Python27\lib\site-packages\serial\serialwin32.py", line 221, in read
if not self.hComPort: raise portNotOpenError

ValueError: Attempting to use a port that is not open

UPDATE

The code from @Blender answer below is probably correct. The issue now
I am having is I’m getting “SerialException: could not open port
COM5: [Error 5] Access is denied.”

However, if I run my original, on.py or off.py script individually, it
works fine…I don’t see how the new code is not working…unless does
it try to open COM5 twice??

END UPDATE

I trying to run multiple python functions, or separate .py scripts, using Flask; in order to generate separate URLs. Just trying to turn the Arduino ON/OFF running it locally.

For example, I have on.py and off.py and want to build sever.py.
So, when I open 127.0.0.1:5000/on it runs on.py, similarly 127.0.0.1:5000/off runs off.py,

After a few hours, I just decided to add both .py functions into the server.py, but of course it doesn’t work…I think I just don’t understand the parameters usage.

Really thank you in advance!

## Open a serial connection with Arduino.

from time import sleep
from arduino import Arduino

from flask import Flask


b = Arduino("COM5",9600)
pin = 13
num = 5

ON = Flask("Light_ON")
OFF = Flask("Light_OFF")


def LightON():
    #declare output pins as a list/tuple
    b.output([pin])
    b.setHigh(pin)
    b.close()
    return 'Light is ON'

def LightOFF():
    #declare output pins as a list/tuple
    b.output([pin])
    b.setLow(pin)
    return 'Light is OFF'

@ON.route('/ON')
@OFF.route('/OFF')

ON.run()
OFF.run()  //I know this doesn't run, just not sure how to include it.
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1 Answer

  1. Editorial Team

    Something like this should work:

    from arduino import Arduino
from flask import Flask

app = Flask('light_control')
board = Arduino('COM5', 9600)
pin = 13

@app.route('/on')
def light_on():
    board.output([pin])
    board.setHigh(pin)
    board.close()

    return 'Light is ON'

@app.route('/off')
def light_off():
    board.output([pin])
    board.setLow(pin)
    # board.close() ???

    return 'Light is OFF'

if __name__ == '__main__':
    app.debug = True
    app.run()
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