Short introduction

Opening serial ports

Open port 0 at “9600,8,N,1”, no timeout:

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

Open named port at “19200,8,N,1”, 1s timeout:

>>> ser = serial.Serial('/dev/ttyS1', 19200, timeout=1)
>>> x = ser.read()          # read one byte
>>> s = ser.read(10)        # read up to ten bytes (timeout)
>>> line = ser.readline()   # read a '\n' terminated line
>>> ser.close()

Open second port at “38400,8,E,1”, non blocking HW handshaking:

>>> ser = serial.Serial(1, 38400, timeout=0,
...                     parity=serial.PARITY_EVEN, rtscts=1)
>>> s = ser.read(100)       # read up to one hundred bytes
...                         # or as much is in the buffer

Configuring ports later

Get a Serial instance and configure/open it later:

>>> ser = serial.Serial()
>>> ser.baudrate = 19200
>>> ser.port = 0
>>> ser
Serial<id=0xa81c10, open=False>(port='COM1', baudrate=19200, bytesize=8, parity='N', stopbits=1, timeout=None, xonxoff=0, rtscts=0)
>>> ser.open()
>>> ser.isOpen()
True
>>> ser.close()
>>> ser.isOpen()
False

Readline

Be carefully when using “readline”. Do specify a timeout when opening the serial port otherwise it could block forever if no newline character is received. Also note that “readlines” only works with a timeout. “readlines” depends on having a timeout and interprets that as EOF (end of file). It raises an exception if the port is not opened correctly.

Do also have a look at the example files in the examples directory in the source distribution or online.

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