Python通过pyserial控制串口操作

      你想通过串行端口读写数据,典型场景就是和一些硬件设备打交道(比如一个机器人或传 感器)。 尽管你可以通过使用Python内置的I/O模块来完成这个任务,但对于串行通信最好的选择 是使用 pySerial包 。 这个包的使用非常简单,先安装pySerial,使用类似下面这样的代码 就能很容易的打开一个串行端口:

一、用python操作串口，首先需要下载相关模块:

 pyserial (http://pyserial.wiki.sourceforge.net/pySerial)

 pywin32 (http://sourceforge.net/projects/pywin32/)

import serial
ser = serial . Serial('/dev/tty.usbmodem641', # Device name varies
                      baudrate = 9600,
                      bytesize = 8,
                      parity = 'N',
                      stopbits = 1)

设备名对于不同的设备和操作系统是不一样的。 比如,在Windows系统上,你可以使用0,1等表示的一个设备来打开通信端”COM0”和”COM1”。 一旦端口打开,那就可以使用read() , readline() 和 write() 函数读写数据了。

二,十六进制显示

       十六进制显示的实质是把接收到的字符转换成其对应的ASCII码，然后将ASCII码值再转换成十六进制数显示出来，这样就可以显示特殊字符了。在这里定义了一个函数，如hexShow(argv)，代码如下：

[python] view plain copy

import serial  

  
def hexShow(argv):  
    result = ''  
    hLen = len(argv)  
    for i in xrange(hLen):  
        hvol = ord(argv[i])  
        hhex = '%02x'%hvol  
        result += hhex+' '  
    print 'hexShow:',result  
  
t = serial.Serial('com12',9600)  
print t.portstr  
strInput = raw_input('enter some words:')  
n = t.write(strInput)  
print n  
str = t.read(n)  
print str  
hexShow(str) 

3,十六进制发送

十六进制发送实质是发送十六进制格式的字符串，如'\xaa'，'\x0b'。重点在于怎么样把一个字符串转换成十六进制的格式，有两个误区：

1）'\x'+'aa'是不可以，涉及到转义符反斜杠

2）'\\x'+'aa'和r'\x'+'aa'也不可以，这样的打印结果虽然是\xaa，但赋给变量的值却是'\\xaa'

 这里用到decode函数，

[python] view plain copy

list='aabbccddee'  
hexer=list.decode("hex")  
print  hexer  

需要注意一点，如果字符串list的长度为奇数，则decode会报错，可以按照实际情况，用字符串的切片操作，在字符串的开头或结尾加一个'0'

 

假如在串口助手以十六进制发送字符串"abc"，那么你在python中则这样操作“self.l_serial.write(”\x61\x62\x63") ”

当然，还有另外一个方法：

[python] view plain copy

strSerial = "abc"  
strHex = binascii.b2a_hex(strSerial)  
#print strHex  
strhex = strHex.decode("hex")  
#print strhex  
self.l_serial.write(strhex);  

Short introduction

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

Get a Serial instance and configure/open it later 

>>> 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

Parameters for the Serial class

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: 

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

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: 

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: 

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

serial.SerialException

Constants

parity: 

    serial.PARITY_NONE
serial.PARITY_EVEN
serial.PARITY_ODD

stopbits: 

    serial.STOPBITS_ONE
serial.STOPBITS_TWO

bytesize: 

    serial.FIVEBITS
serial.SIXBITS
serial.SEVENBITS
serial.EIGHTBITS