Having errors working with com ports using pyserial

Question

I am trying to interface with my com ports, specifically an XBee connected to thi using this code.

from xbee import XBee
from serial import Serial

PORT = 'COM3'
BAUD = 9600

ser = Serial(PORT, BAUD)

xbee = XBee(ser)
# Send the string 'Hello World' to the module with MY set to 1
xbee.tx(dest_addr='\x00\x01', data='Hello World')

# Wait for and get the response
print(xbee.wait_read_frame())

ser.close()

However, this error keeps arising.

SerialException: could not open port 'COM3': WindowsError(5, 'Access is denied.'). It goes away when I restart my computer, buts it keeps returning. I'd prefer to understand why its happening so I don't need to keep restarting my computer. Would really appreciate any help, thanks. I am working through the IDLE interface with python 2.7 just in case that is relevant.

Paul Cornelius · Accepted Answer · 2016-07-08 23:46:12Z

1

A serial port can be "open" in only one application at a time. Once application "A" opens the port, application "B" will get an Access Denied error when it tries to open the same port. In your case, you need to figure out what other application is holding the port and close it first.

answered Jul 8, 2016 at 23:46

Paul Cornelius

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2 Comments

Zotto Over a year ago

I exited XCTU program, and I am not getting the error anymore, but how can I have the program running and use the XBees?

Paul Cornelius Over a year ago

I've never heard of XBees. But the OS cannot logically allow two different applications to use the same port simultaneously, just as it cannot allow two applications to write to the same disk file simultaneously. There is no way to prevent data corruption in case of collisions. If your XBees library is controlling the serial port, you need to work with its API and forget about PySerial.

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