转:Python通过pyserial控制串口操作

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https://blog.csdn.net/lovelyaiq/article/details/48101487

 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:

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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,

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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(”x61x62x63") ”

当然,还有另外一个方法:


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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
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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 ‘ ‘ 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

>>> 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

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  
    al.STOPBITS_TWO  

bytesize:
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        serial.FIVEBITS  
    serial.SIXBITS  
    serial.SEVENBITS  
    serial.EIGHTBITS  
---------------------
作者:TiRan_Yang
来源:CSDN
原文:https://blog.csdn.net/lovelyaiq/article/details/48101487
版权声明:本文为博主原创文章,转载请附上博文链接!

 

































































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