Assign variable to pyserial port

Question

I must assign to serial port a variable.

ser = serial.Serial(
port=VARIABLE
baudrate=115200,
parity=serial.PARITY_NONE,
stopbits=serial.STOPBITS_ONE,
bytesize=serial.EIGHTBITS
)

I try with port=VARIABLE, but that doesn't work. It seems to accept only path but in my program I have many device.

score 1 · Accepted Answer · edited May 23 '17 at 11:59

As I understand, you have several devices on com ports and you would like to select one of them and assign that port to VARIABLE.

Below is a code that reads COM port and assigns first port as usable COM port. It then probes the COM port to see if its open.

You can inspect serial_ports() output to determine which COM PORT you want to use and assign the respective port slice accordingly to VARIABLE. I've used port 0 which is my COM1

The function serial_ports() is cross platform. I have windows and it works seamlessly.

Inspiration from here

Demo Code

import sys
import glob
import serial


def serial_ports():

    if sys.platform.startswith('win'):
        ports = ['COM%s' % (i + 1) for i in range(256)]
    elif sys.platform.startswith('linux') or sys.platform.startswith('cygwin'):
        # this excludes your current terminal "/dev/tty"
        ports = glob.glob('/dev/tty[A-Za-z]*')
    elif sys.platform.startswith('darwin'):
        ports = glob.glob('/dev/tty.*')
    else:
        raise EnvironmentError('Unsupported platform')

    result = []
    for port in ports:
        try:
            s = serial.Serial(port)
            s.close()
            result.append(port)
        except (OSError, serial.SerialException):
            pass
    return result


if __name__ == '__main__':

    VARIABLE = serial_ports()[0] #Assign first port as COM port    
    ser = serial.Serial(
    port=VARIABLE,
    baudrate=115200,
    parity=serial.PARITY_NONE,
    stopbits=serial.STOPBITS_ONE,
    bytesize=serial.EIGHTBITS
    )

    print "Is port", VARIABLE , " open ?", ser.isOpen()

Output

Python 2.7.9 (default, Dec 10 2014, 12:24:55) [MSC v.1500 32 bit (Intel)] on win32
Type "copyright", "credits" or "license()" for more information.
>>> ================================ RESTART ================================
>>> 
Is port COM1  open ? True
>>>

Assign variable to pyserial port

1 Answers1