Open port at "9600,8,N,1", no timeout:
>>> import serial
>>> ser = serial.Serial('/dev/ttyUSB0') # open serial port
>>> print(ser.name) # check which port was really used
>>> ser.write(b'hello') # write a string
>>> ser.close() # close port
Open named port at "19200,8,N,1", 1s timeout:
>>> with serial.Serial('/dev/ttyS1', 19200, timeout=1) as ser:
... x = ser.read() # read one byte
... s = ser.read(10) # read up to ten bytes (timeout)
... line = ser.readline() # read a '\n' terminated line
Open port at "38400,8,E,1", non blocking HW handshaking:
>>> ser = serial.Serial('COM3', 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
Get a Serial instance and configure/open it later:
>>> ser = serial.Serial()
>>> ser.baudrate = 19200
>>> ser.port = 'COM1'
>>> 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.is_open
True
>>> ser.close()
>>> ser.is_open
False
Also supported with context manager:
serial.Serial() as ser:
ser.baudrate = 19200
ser.port = 'COM1'
ser.open()
ser.write(b'hello')
Be careful 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.
Note
The eol
parameter for readline
is no longer supported when pySerial is run with newer Python versions (V2.6+) where the module io
is available.
To specify the EOL character for readline
or to use universal newline mode, it is advised to use io.TextIOWrapper:
import serial
import io
ser = serial.serial_for_url('loop://', timeout=1)
sio = io.TextIOWrapper(io.BufferedRWPair(ser, ser))
sio.write(unicode("hello\n"))
sio.flush() # it is buffering. required to get the data out *now*
hello = sio.readline()
print(hello == unicode("hello\n"))
python -m serial.tools.list_ports
will print a list of available ports. It is also possible to add a regexp as first argument and the list will only include entries that matched.
Note
The enumeration may not work on all operating systems. It may be incomplete, list unavailable ports or may lack detailed descriptions of the ports.
pySerial includes a small console based terminal program called miniterm
. It ca be started with python -m serial.tools.miniterm <port_name>
(use option -h
to get a listing of all options).