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python 自动识别并连接串口 python 自动识别并连接串口的实现

菜鸡学长   2021-01-19 我要评论

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

在这里插入图片描述

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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