使用python来调试串口

串口模块的波特率比较特别，找了几个串口工具都不支持。。。所以，干脆用python自己来写了，其实已经好奇好久了，别人的工具各种不顺手。

需要pyserial的支持，兼容各种平台，不需要新编译二进制文件。

先贴一个定时发送的代码：

import serial
import time

ser = serial.Serial('/dev/ttyUSB0', 250000, timeout=1)
print ser.isOpen()
words="gggggggggggggggg"

while (1):
        print "send 256x""+words+"" to remotes"
        startTime = time.time()
        times = 256
        while (times):
                times -= 1
                s = ser.write(words)

        endTime = time.time()
        print "use time: "+str(endTime-startTime)
        print ""
        time.sleep(5)
ser.close()

然后是一些其它的方法：

1. 使用序号打开串口：ser = serial.Serial(0) 。but，怎么确定串口的序号？？？

2. 查看串口的名称，啊哈，用1的方法打开串口后，你可以产看串口的名字：print ser.portstr  

3. 先例化一个实体，再打开：

>>> 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

好多人问 windows 下面提示设备不存在！亲，windows 下面的串口设备名不一样的啊，上面的代码里面 COM1 就是 windows 下面的设备。

4. 读取数据的几种方式

>>> 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()

其中，如果只是串口调试，直接ser.read(1000)，这样会把读到的值直接打印到屏幕上。

5.所有参数

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
)

6. exception：serial.SerialException

另一个完整收发的例子，单片机数据以TLV（Type，Length，Value）格式发上来

#!/usr/bin/env python
# it's a program of luo, piedgogo@sina.com

import serial
import array
import os
import signal
from time import sleep

flag_stop = False

def onsignal_int(a,b):
    print "sigint!"
    global flag_stop
    flag_stop = True

signal.signal(signal.SIGINT, onsignal_int)
signal.signal(signal.SIGTERM, onsignal_int)

ser = serial.Serial('/dev/ttyUSB0', 9600, timeout = 0.001)
print "serial.isOpen() =",ser.isOpen()

cmd_send = "7b02000129cc00c80378290400640000cc7d0d0a"
cmd_send = cmd_send.decode("hex")

stop = "7b04047d0d0a"
stop = stop.decode("hex")

cmd_back = ""
cmd_length = 0x00
cmd_count = 0x00

s = ser.write(cmd_send)

while True:
    sleep(0.1)
    
    if flag_stop:                # read data until Ctrl+c
        ser.write(stop)            # send cmd stop before exit
        print "reset cmd has been sent!"
        sleep(0.05)
        break
    
    text = ser.read(1)          # read one, with timout
    if text:                    # check if not timeout
        n = ser.inWaiting()     # look if there is more to read
        if n:
            text = text + ser.read(n) #get it
        cmd_back = cmd_back + text
        text = ""

    if len(cmd_back) < 2:        # go back if no enough data recvd
        continue
    
    if cmd_length == 0x00:                        # new loop
        cmd_length = ord(cmd_back[1])            # Type(1 byte),Length of Value(1 byte),Value
        print "new cmd length,",cmd_length        
    
    if (cmd_length + 0x02) > len(cmd_back):        # do nothing until all bytes is recvd
        continue
    
    # so far, we have got a full cmd

    hex_list = [hex(ord(i)) for i in cmd_back]    # more readable than data.encode("hex")
    print "In buffer:",hex_list

    cmd_back = cmd_back[cmd_length+2:]            # remove this cmd(TLV) from buffer
    cmd_length = 0
    cmd_count += 1

    print "==> %d cmds recvd."%(cmd_count)
    print "-------------"    
    
ser.close()

可用的串口列表，可以用下面的方法获取：

python -c "import serial.tools.list_ports;print [port for port in serial.tools.list_ports.comports() if port[2] != 'n/a']"

因为获取的列表里可能有“假冒”的，所以，上面的代码还检查了设备的 hwid。comports() 返回的是一个 list，元素是一个对象，查看其 type() 结果如下 ：

type(port)

class 'serial.tools.list_ports_linux.SysFS'

查看文档 pydoc serial.tools.list_ports_linux.SysFS，上面的 port[2] 是这个 port 的 hwid，另外还有 port[0] 是串口名称，port[1]是 description 。