Python通过pyserial控制串口操作
2015-08-30 07:48
1111 查看
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:
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
4000
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);
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
Options for read timeout:
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
4000
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 portOpen 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<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
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 widthsNew 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_ODDstopbits:
serial.STOPBITS_ONE serial.STOPBITS_TWObytesize:
serial.FIVEBITS serial.SIXBITS serial.SEVENBITS serial.EIGHTBITS
相关文章推荐
- Python工具
- Python 遍历文件查找不同
- 初探python的__init__.py
- 简单Python脚本实现数据导出Excel格式的尝试
- 【python】strip()的用法
- 【python】socket编程常量错误问题-1 'AF_INET'
- 2015/8/29 Python基础(3):数值
- Python 自学笔记(二)第一个程序 Hello World
- Python中文分词组件jieba
- Python 2.7和NLTK安装教程
- python使用xmlrunner模块生成报告举例
- Python 自学笔记(一)环境搭建
- Setup Python 开发环境和IPython的基本使用
- 零基础学python-9.2 文件
- 零基础学python-9.2 文件
- python常用函数
- python字符串操作
- python学习笔记10
- 关于python文件操作
- Python计算代码段的时间