Python Pyserial Windows No Port Found

Question

I have just tried to connect to usb mobile to send sms through it using AT commands. But when i use pyserial to connect to it in a windows os, i get error could not open port, the file specified cannot be found.

>>> import serial
>>> ser = serial.Serial(0)  # open first serial port
>>> print ser.name          # check which port was really used
>>> ser.write("hello")      # write a string
>>> ser.close()

even if i replace the 0 with any other value, like 0 -10 or 'com0','com1' etc, i still get error file specified not found, port cannot be open.

There is a command listed in pyserial documentation which lists ports or allows you to open a port

python -m serial.tools.miniterm

This command is supposed to list all serial ports. But it shows none.

I have 3 usb ports on my system. What is causing this issue.

Have you tried COM0 and such in caps? I'm not sure if it matters.. also maybe USB0 ..? I'm not really sure. maybe this is what you're aiming for pyserial.sourceforge.net/pyserial_api.html?highlight=usb#urls ? — Tony

rask004 rask004 · Accepted Answer · 2015-04-23T04:39:12

Pyserial is not guaranteed to detect all ports. This depends on how the device and the OS communicate and if pyserial is designed to pick up on this. For Example, pyserial could not detect a LabJack U3-LV or a EPSOM-POS receipt printer I plugged in in a Win8 session (both could be detected using a linux session).

Try serial.tools.list_ports.comports() and see what it gives you.

You could also look at the pyusb module for usb connections.

Also: I recommend being careful when using numbers for ports, as the mapping may not be "common-sense" logical (i.e. 0 may not map to COM0). Use explicit string names instead.

Python Pyserial Windows No Port Found

2 Answers