Python to automatically select serial ports (for A

Question

Currently the python program must know which port a device (Arduino) is on before Python can communicate the device.

Problem: Whenever the device is plugged out and back in, its COM port changes, so the correct serial port must be given to Python again for it to find the device.

How can Python (using pySerial) automatically search for the correct serial port to use? Is it possible for python to correctly identify the device on a serial port as an Arduino?

Answer 1

Use the following code to see all the available serial ports:

import serial.tools.list_ports
ports = list(serial.tools.list_ports.comports())
for p in ports:
    print p

This gives me the following:

('COM4', 'Arduino Due Programming Port (COM4)', 'USB VID:PID=2341:003D SNR=75330303035351300230')
('COM11', 'RS-232 Port (COM11)', 'FTDIBUS\\VID_0856+PID_AC27+BBOPYNPPA\\0000')

To work out if it's an Arduino you could do something like:

    if "Arduino" in p[1]:
        print "This is an Arduino!"

Answer 2

Using serial.tools.list_ports.comports, we can find and connect to an arduino with:

import warnings
import serial
import serial.tools.list_ports

arduino_ports = [
    p.device
    for p in serial.tools.list_ports.comports()
    if 'Arduino' in p.description
]
if not arduino_ports:
    raise IOError("No Arduino found")
if len(arduino_ports) > 1:
    warnings.warn('Multiple Arduinos found - using the first')

ser = serial.Serial(arduino_ports[0])

If you know you're looking for exactly the same arduino each time, you can filter on p.serial_number instead

import serial.tools.list_ports

def find_arduino(serial_number):
    for pinfo in serial.tools.list_ports.comports():
        if pinfo.serial_number == serial_number:
            return serial.Serial(pinfo.device)
    raise IOError("Could not find an arduino - is it plugged in?")

ser = find_arduino(serial_number='85430353531351B09121')

Answer 3

"""
Written on a Windows 10 Computer, Python 2.7.9 Version.

This program automatically detects and lists ports.  If no ports are found, it simply shells out.  In the printout below "list(serial.tools.list_ports.comports())" finds two ports and the program lists them out - a listout shown below:

     COM5 - USB-SERIAL CH340 (COM5)
     Found Arduino Uno on COM5
     COM4 - Microsoft USB GPS Port (COM4)

As each port is found, "CH340," (the name of the Adruino Uno) is searched for in the listed port with the "while int1 < 9:" loop.  The first "If" statement looks for "CH340" and when found the integer value "int1" will be the same as the com port #. With a concatination,  the operation "str1 = "COM" + str2" gives the com port name of the Adruino, eg. "COM5."  The next "IF" statement looks for both "CH340" AND str1, ("COM5") in the above case.  The statement "Found Arduino Uno on COM5" prints out, and "str1" is used in setting up the com port:

ser = serial.Serial(str1, 9600, timeout=10)

This program goes on to open the com port and prints data from the Adruino.

The modules "serial, sys, time, serial.tools.list_ports" must all be imported.

Written by Joseph F. Mack 01/29/2016.  "A BIG Thank you" to all the individuals whose programs I "borrowed" from that are available in the many forums for Python and PYGame users!
"""

import serial
import sys
import time
import serial.tools.list_ports

serPort = ""
int1 = 0
str1 = ""
str2 = ""

# Find Live Ports
ports = list(serial.tools.list_ports.comports())
for p in ports:
   print p # This causes each port's information to be printed out.
           # To search this p data, use p[1].

   while int1 < 9:   # Loop checks "COM0" to "COM8" for Adruino Port Info. 

      if "CH340" in p[1]:  # Looks for "CH340" in P[1].
            str2 = str(int1) # Converts an Integer to a String, allowing:
            str1 = "COM" + str2 # add the strings together.

      if "CH340" in p[1] and str1 in p[1]: # Looks for "CH340" and "COM#"
         print "Found Arduino Uno on " + str1
         int1 = 9 # Causes loop to end.

      if int1 == 8:
         print "UNO not found!"
         sys.exit() # Terminates Script.

      int1 = int1 + 1

time.sleep(5)  # Gives user 5 seconds to view Port information -- can be   changed/removed.

# Set Port
ser = serial.Serial(str1, 9600, timeout=10) # Put in your speed and timeout value.

# This begins the opening and printout of data from the Adruino.

ser.close()  # In case the port is already open this closes it.
ser.open()   # Reopen the port.

ser.flushInput()
ser.flushOutput()

int1 = 0
str1 = ""
str2 = ""

while int1==0:

   if "\n" not in str1:        # concatinates string on one line till a line feed "\n"
      str2 = ser.readline()    # is found, then prints the line.
      str1 += str2
   print(str1)
   str1=""
   time.sleep(.1)

print 'serial closed'
ser.close()