python 自动识别并连接串口的实现

这个属于我项目中一个函数，跟大家分享一下我的思路及最终实现

在编写串口通信工具中，需要实现一个函数，自动找到对应com 口，并且连接该com口，保证后续通信正常
作为初始化过程的一部分。

思路

在win 设备管理器中，经常会出现多个com 口，但并不是每个com 口都是目标设备所链接的。
尝试打开每个com 口，输入enter 按键， 正确的com 口，会有ack log 返回，表明通信 正常

否则，没有任何log 返回，则判断为非目标设备所连接的com 口。

实现

尝试去打开所有com 口，然后发送enter， 如果在一段时间内有返回值，检查com 口收到的字节数，如果非零，则表明找到了对应的com 口。

完整测试代码如下：

import serial
import serial.tools.list_ports
import threading
import binascii
import time
from datetime import datetime

# default value
baunRate = 115200
is_read = False
is_write = False
write_buff = []
sys_buff = []
mSerial = None
callback = None
is_opened = 0
is_registed = 0

class SerialPort:

  def __init__(self,port,buand):

    self.port = serial.Serial(port,buand)
    self.port.close()
    if not self.port.isOpen():
      self.port.open()

    #the index of data_bytes for read operation,私有属性
    #only used in read lines
    self.__read_ptr = 0
    self.__read_head = 0
    #store all read bytes
    # used in read date， read lines
    self.__data_bytes = bytearray()

  def port_open(self):
    if not self.port.isOpen():
      self.port.open()

  def port_close(self):
    self.port.close()

  def send(self):
    global is_write
    global write_buff

    while is_write:
      if len(write_buff):
        msg = write_buff.pop(0)
        msg = msg+"\n"
        cmd = msg.encode()
        try:

          self.port.write(cmd)
        except:
          write_buff.clear()
          is_write = False
    write_buff.clear()

  def read_data(self):
    global is_read
    global is_opened
    byte_cnt = 0
    while is_read:
      try:
        count = self.port.inWaiting()
        if count > 0:
          rec_str = self.port.read(count)
          self.__data_bytes = self.__data_bytes+rec_str
        #print("receive:",rec_str.decode())
          #print(rec_str)
          byte_cnt += count
          if not is_opened:
            is_opened = 1
      #print("累计收到：",byte_cnt)
      #time.sleep(0.5)
        self.read_lines()
      except:
        deinit()

  #将当前所有的数据都读出，读取位置不变，每次读取指针依次移动，不漏数据， 读取行为一直在进行
  def read_lines(self):
    #reset
    line_cnt = 0
    data_len = len(self.__data_bytes)
    #print ("")
    #print ("begin: prt=:", self.__read_ptr, " head =", self.__read_head,"current len =",data_len)
    if self.__read_ptr >=data_len:
      return
    #get all lines in current data_bytes
    while(self.__read_ptr < data_len-1):
      if(self.__data_bytes[self.__read_ptr+1] == 0x0a and self.__data_bytes[self.__read_ptr] == 0x0d):
        tmp = bytearray()
        tmp = self.__data_bytes[self.__read_head:self.__read_ptr]

        try:
          line = tmp.decode()
        except:
          self.__read_head = self.__read_ptr + 2
          self.__read_ptr = self.__read_head
          continue
        iprint(line)
        line_cnt += 1
        self.__read_head = self.__read_ptr + 2
        self.__read_ptr = self.__read_head
      else:
        self.__read_ptr = self.__read_ptr + 1

def auto_open_serial():
  global baunRate
  global mSerial
  global callback
  global is_registed
  global is_opened
  #reset
  deinit()
  # 列出所有当前的com口
  port_list = list(serial.tools.list_ports.comports())
  port_list_name = []
  #get all com
  if len(port_list) <= 0:
    iprint("the serial port can't find!")
    return False
  else:
    for itms in port_list:
      port_list_name.append(itms.device)
  #try open
  #print(port_list_name)
  for i in port_list_name:
    try:
      mSerial = SerialPort(i,baunRate)
      iprint("try open %s"%i)
      start_task()
      send("")
      #return True
      time.sleep(1)
      if is_opened:
        iprint("connect %s successfully"%i)
        return True
      else:
        deinit()
        if i == port_list_name[len(port_list_name)-1]:
          iprint("uart don't open")
          break
        continue
    except:
      iprint(" uart don't open")
  deinit()
  return False

def deinit():
  global mSerial
  global is_write
  global is_read
  global write_buff
  global is_opened

  if mSerial:
    mSerial.port_close()

  is_opened = 0
  is_read = False
  is_write = False
  write_buff = []

  mSerial = None
  time.sleep(1)

def init():
  global mSerial
  global callback
  global is_registed
  global is_opened
  global is_read
  global is_write
  #retry
  retry_time = 0
  while not auto_open_serial():
    if not is_opened:
      iprint("wait for uart connect, retry %s"%str(retry_time))
    else:
      return True
    retry_time += 1
    time.sleep(2)
    if retry_time == 10:
      iprint(" open uart fail")
      return False

def send(msg):
  global mSerial
  global is_write
  global write_buff
  if is_write:
    write_buff.append(msg)

def start_task():
  global mSerial
  global is_write
  global is_read

  if mSerial:
    is_write = True
    t1 = threading.Thread (target=mSerial.send)
    t1.setDaemon (False)
    t1.start ()

    is_read = True
    t2 = threading.Thread (target=mSerial.read_data)
    t2.setDaemon (False)
    t2.start ()

def iprint(msg):
  global callback
  global is_registed

  msg = "[Uart] "+str(msg)
  if is_registed:
    callback.append(msg)
  else:
    print(msg)

def start_sys_cmd():
  global is_registed
  if is_registed:
    t3 = threading.Thread (target=process_receive_sys_cmd)
    t3.setDaemon (False)
    t3.start()

def process_receive_sys_cmd():
  global sys_buff
  global is_registed
  global callback
  #print("process_receive_sys_cmd")
  while is_registed:
    #print ("wait,process_receive_sys_cmd")
    if len(sys_buff):
      #print ("receive,process_receive_sys_cmd")
      line = sys_buff.pop(0)
      if "init" in line:
        if is_opened and is_read and is_write:
          iprint("already open uart")
          break
        iprint("start init")
        init()
    if is_opened:
      break
  iprint("Eixt uart sys thread")

def register_cback(list):
  global callback
  global is_registed

  callback = list
  is_registed = 1

def unregister_cback():
  global callback
  callback.clear()

if __name__ == '__main__':

  receive = []
  register_cback(receive)
  sys_buff.append("init")
  start_sys_cmd()

  def process_receive_msg():
    global receive
    while True:
      #print("wait")
      if len(receive):
        #print("receive")
        print(receive.pop(0))

  t = threading.Thread(target=process_receive_msg)
  t.setDaemon(False)
  t.start()

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