树莓派python串口_树莓派RaspberryPi串口Python操作指南

Overview

This module encapsulates the access for the serial port. It provides backends for Python running on Windows, Linux, BSD (possibly any POSIX compliant system), Jython and IronPython (.NET and Mono). The module named "serial" automatically selects the appropriate backend.

It is released under a free software license, see LICENSE.txt

for more details.

(C) 2001-2008 Chris Liechti cliechti@gmx.net

The project page on SourceForge

and here is the SVN repository

and the Download Page

.

The homepage is on http://pyserial.sf.net/

Features

same class based interface on all supported platforms

access to the port settings through Python 2.2+ properties

port numbering starts at zero, no need to know the port name in the user program

port string (device name) can be specified if access through numbering is inappropriate

support for different bytesizes, stopbits, parity and flow control with RTS/CTS and/or Xon/Xoff

working with or without receive timeout

file like API with "read" and "write" ("readline" etc. also supported)

The files in this package are 100% pure Python. They depend on

non standard but common packages on Windows (pywin32) and Jython

(JavaComm). POSIX (Linux, BSD) uses only modules from the standard

Python distribution)

The port is set up for binary transmission. No NULL byte

stripping, CR-LF translation etc. (which are many times enabled for

POSIX.) This makes this module universally useful.

Requirements

Python 2.2 or newer

pywin32 extensions on Windows

"Java Communications" (JavaComm) or compatible extension for Java/Jython

Installation

from source

Extract files from the archive, open a shell/console in that directory and let Distutils do the rest:

python setup.py install

The files get installed in the "Lib/site-packages" directory.

easy_install

An EGG is available from the Python Package Index: http://pypi.python.org/pypi/pyserial

easy_install pyserial

windows installer

There is also a Windows installer for end users. It is located in the Download Page

Developers may be interested to get the source archive, because it contains examples and the readme.

Short introduction

Open port 0 at "9600,8,N,1", no timeout

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>>> 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

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>>> 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

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>>> 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

Get a Serial instance and configure/open it later

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>>> ser = serial.Serial()

>>> ser.baudrate = 19200

>>> ser.port = 0

>>> ser

Serial(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

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.

Examples

Please look in the SVN Repository. There is an example directory where you can find a simple terminal and more.

http://pyserial.svn.sourceforge.net/viewvc/pyserial/trunk/pyserial/examples/

Parameters for the Serial class

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ser = serial.Serial(

port=None, # number of device, numbering starts at

# zero. if everything fails, the user

# can specify a device string, note

# that this isn't portable anymore

# if no port is specified an unconfigured

# an closed serial port object is created

baudrate=9600, # baud rate

bytesize=EIGHTBITS, # number of databits

parity=PARITY_NONE, # enable parity checking

stopbits=STOPBITS_ONE, # number of stopbits

timeout=None, # set a timeout value, None for waiting forever

xonxoff=0, # enable software flow control

rtscts=0, # enable RTS/CTS flow control

interCharTimeout=None # Inter-character timeout, None to disable

)

The port is immediately opened on object creation, if a port is given. It is not opened if port is None.

Options for read timeout:

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timeout=None # wait forever

timeout=0 # non-blocking mode (return immediately on read)

timeout=x # set timeout to x seconds (float allowed)

Methods of Serial instances

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open() # open port

close() # close port immediately

setBaudrate(baudrate) # change baud rate on an open port

inWaiting() # return the number of chars in the receive buffer

read(size=1) # read "size" characters

write(s) # write the string s to the port

flushInput() # flush input buffer, discarding all it's contents

flushOutput() # flush output buffer, abort output

sendBreak() # send break condition

setRTS(level=1) # set RTS line to specified logic level

setDTR(level=1) # set DTR line to specified logic level

getCTS() # return the state of the CTS line

getDSR() # return the state of the DSR line

getRI() # return the state of the RI line

getCD() # return the state of the CD line

Attributes of Serial instances

Read Only:

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portstr # device name

BAUDRATES # list of valid baudrates

BYTESIZES # list of valid byte sizes

PARITIES # list of valid parities

STOPBITS # list of valid stop bit widths

New values can be assigned to the following attributes, the port will be reconfigured, even if it's opened at that time:

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port # port name/number as set by the user

baudrate # current baud rate setting

bytesize # byte size in bits

parity # parity setting

stopbits # stop bit with (1,2)

timeout # timeout setting

xonxoff # if Xon/Xoff flow control is enabled

rtscts # if hardware flow control is enabled

Exceptions

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serial.SerialException

Constants

parity:

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serial.PARITY_NONE

serial.PARITY_EVEN

serial.PARITY_ODD

stopbits:

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serial.STOPBITS_ONE

serial.STOPBITS_TWO

bytesize:

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