python 3下对stm32串口数据做解析

1、最近有个想做一个传感器数据实时显示的上位机，常规的数据打印太频繁了，无法直观的看出数据的变化。

python下的上位机实现起来简单一点，网上找了一些python界面Tkinter相关资料和python串口的demo.测试实现了简单的数据显示。

Mark 一下问题点：

最大的问题点在于对bytes型数据的拼接：之前的串口解析的代码是在python 2.7平台上实现的，

切换到python3.0之后，测试失踪无法通过。幸而找到了大神相助。

python 2.7code:

  1 import os
  2 import time
  3 import sys, traceback
  4 from serial.serialutil import SerialException
  5 from serial import Serial
  6
  7 import struct
  8 import binascii
  9
 10
 11 class Arduino:
 12     def __init__(self, port="/dev/ttyUSB0", baudrate=115200, timeout=0.5):
 13
 14         self.port = port
 15         self.baudrate = baudrate
 16         self.timeout = timeout
 17         self.encoder_count = 0
 18         self.writeTimeout = timeout
 19         self.interCharTimeout = timeout / 30.
 20
 21         self.WAITING_FF = 0
 22         self.WAITING_AA = 1
 23         self.RECEIVE_LEN = 2
 24         self.RECEIVE_PACKAGE = 3
 25         self.RECEIVE_CHECK = 4
 26         self.HEADER0 = 0xff
 27         self.HEADER1 = 0xaa
 28         self.REC_CMD = 5
 29         self.count   = 0
 30         self.data1   = 0
 31         self.data2   = 0
 32         self.error_flag = 0
 33         self.SUCCESS = 0
 34         self.FAIL = -1
 35
 36         self.receive_state_ = self.WAITING_FF
 37         self.receive_check_sum_ = 0
 38         self.payload_command = ''
 39         self.payload_ack = ''
 40         self.payload_args = ''
 41         self.payload_len = 0
 42         self.byte_count_ = 0
 43         self.receive_message_length_ = 0
 44
 45         self.mutex = threading.Thread.allocate_lock()
 46
 47         # An array to cache analog sensor readings
 48         self.analog_sensor_cache = [None] * self.N_ANALOG_PORTS
 49
 50         # An array to cache digital sensor readings
 51         self.digital_sensor_cache = [None] * self.N_DIGITAL_PORTS
 52
 53     def connect(self):
 54         try:
 55             print "Connecting to Arduino on port", self.port, "..."
 56             self.port = Serial(port=self.port, baudrate=self.baudrate, timeout=self.timeout, writeTimeout=self.writeTimeout)
 57             # The next line is necessary to give the firmware time to wake up.
 58             time.sleep(1)
 59             state_, val = self.get_baud()
 60             if val != self.baudrate:
 61                 time.sleep(1)
 62                 state_, val  = self.get_baud()
 63                 if val != self.baudrate:
 64                     raise SerialException
 65             print "Connected at", self.baudrate
 66             print "Arduino is ready."
 67
 68         except SerialException:
 69             print "Serial Exception:"
 70             print sys.exc_info()
 71             print "Traceback follows:"
 72             traceback.print_exc(file=sys.stdout)
 73             print "Cannot connect to Arduino!"
 74             os._exit(1)
 75
 76     def open(self):
 77         self.port.open()
 78
 79     def close(self):
 80         self.port.close()
 81
 82     def send(self, cmd):
 83         self.port.write(cmd)
 84
 85     def receiveFiniteStates(self, rx_data):
 86         if self.receive_state_ == self.WAITING_FF:
 87             #print str(binascii.b2a_hex(rx_data))
 88             if rx_data == '\xff':
 89                 self.receive_state_ = self.WAITING_AA
 90                 self.receive_check_sum_ =0
 91                 self.receive_message_length_ = 0
 92                 self.byte_count_=0
 93                 self.payload_ack = ''
 94                 self.payload_args = ''
 95                 self.payload_len = 0
 96                 self.count = 0
 97
 98         elif self.receive_state_ == self.WAITING_AA :
 99              if rx_data == '\xaa':
100                  self.receive_state_ = self.REC_CMD
101              else:
102                  self.receive_state_ = self.WAITING_FF
103         elif self.receive_state_ == self.REC_CMD:
104              self.count+=1
105              if self.count == 1:
106                 self.data1,=struct.unpack("B",rx_data)
107              elif self.count == 2:
108                   self.data2,=struct.unpack("B",rx_data)
109                   self.receive_state_ = self.RECEIVE_LEN
110                   if self.error_flag == 0 and self.data1 != 0:
111                      self.error_flag = 1
112                   if self.data2 != 0 and self.error_flag == 0:
113                      self.error_flag = 1
114         elif self.receive_state_ == self.RECEIVE_LEN:
115              self.receive_message_length_, = struct.unpack("B",rx_data)
116              self.receive_state_ = self.RECEIVE_PACKAGE
117         elif self.receive_state_ == self.RECEIVE_PACKAGE:
118              if self.byte_count_==0:
119                  self.payload_ack = rx_data
120              else:
121                  self.payload_args += rx_data
122              self.byte_count_ +=1
123              #print "byte:"+str(byte_count_) +","+ "rece_len:"+str(receive_message_length_)
124              if self.byte_count_ >= self.receive_message_length_:
125                  self.receive_state_ = self.RECEIVE_CHECK
126
127         elif self.receive_state_ == self.RECEIVE_CHECK:
128             #if(rx_data == (unsigned char)receive_check_sum_)
129             if 1:
130                 self.receive_state_ = self.WAITING_FF
131                 #print str(binascii.b2a_hex(value))
132                 #left, right, = struct.unpack('hh', value)
133                 #print "left:"+str(left)+", right:"+str(right)
134                 return 1
135             else:
136                 self.receive_state_ = self.WAITING_FF
137         else:
138             self.receive_state_ = self.WAITING_FF;
139         return 0
140
141     def recv(self, timeout=0.5):
142         timeout = min(timeout, self.timeout)
143         ''' This command should not be used on its own: it is called by the execute commands
144             below in a thread safe manner.  Note: we use read() instead of readline() since
145             readline() tends to return garbage characters from the Arduino
146         '''
147         c = ''
148         value = ''
149         attempts = 0
150         c = self.port.read(1)
151         #print str(binascii.b2a_hex(c))
152         while self.receiveFiniteStates(c) != 1:
153             c = self.port.read(1)
154             #print str(binascii.b2a_hex(c))
155             attempts += 1
156             if attempts * self.interCharTimeout > timeout:
157                 return 0
158         return 1
159
160     def recv_ack(self):
161         ack = self.recv(self.timeout)
162         return ack == 'OK'
163
164     def execute(self, cmd):
165         self.mutex.acquire()
166
167         try:
168             self.port.flushInput()
169         except:
170             pass
171
172         ntries = 1
173         attempts = 0
174
175         try:
176             self.port.write(cmd)
177             res = self.recv(self.timeout)
178             while attempts < ntries and res !=1 :
179                 try:
180                     self.port.flushInput()
181                     self.port.write(cmd)
182                     res = self.recv(self.timeout)
183                 except:
184                     print "Exception executing command: " + str(binascii.b2a_hex(cmd))
185                 attempts += 1
186         except:
187             self.mutex.release()
188             print "Exception executing command: " + str(binascii.b2a_hex(cmd))
189             return 0
190
191         self.mutex.release()
192         return 1
193
194     def get_baud(self):
195         ''' Get the current baud rate on the serial port.
196         '''
197         cmd_str=struct.pack("4B", self.HEADER0, self.HEADER1, 0x01, 0x00) + struct.pack("B", 0x01)
198         if (self.execute(cmd_str))==1 and self.payload_ack == '\x00':
199            val, = struct.unpack('I', self.payload_args)
200            return  self.SUCCESS, val
201         else:
202            return self.FAIL, 0
203
204     def get_check_sum(self,list):
205         list_len = len(list)
206         cs = 0
207         for i in range(list_len):
208             #print i, list[i]
209             cs += list[i]
210         cs=cs%255
211         return cs
212
213     def stop(self):
214         ''' Stop both motors.
215         '''
216         self.drive(0, 0)

View Code

在python 3.6 version 中就该修改部分代码：

问题在于bytes类型的拼接：

以下的拼接是正确的：

bytes('','ascii')+bytes([1,2,3,4,5,6,7,8,9])bytes('','ascii')+bytes([1,2,3,4,5,6,7,8,9])+bytes([1,2,3,4,5,6,7,8,9])

也即是：bytes类型的拼接的初始变量要声明为：bytes('','ascii')

如果声明为其它类型：比如字符串，执行时会直接报错。

即：python2.7代码块中：40行以及94行的声明：

（1）将：40行和94行的
self.payload_args = ''
改为：
self.payload_args = bytes('','ascii')
（2）将：121行赋值命令：
self.payload_args += rx_data
修改为：
self.payload_args +=  bytes（rx_data）

View Code

源码已上传到github：链接

目前单纯实现了串口数据的查询：

转载于:https://www.cnblogs.com/sshbit/p/10283185.html

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