我正在尝试使用Python读取二进制串行端口。每个源消息包含3个浮点值,共12个字节。使用下面显示的Python代码,我期望收到12字节的bytearray
消息。但是,运行我发现的代码并不总是12个字节,有时甚至是乱码。我在这里做错什么或为什么会这样?
Pyhon代码:
#!/usr/bin/env python
import serial
import time
serialPort = 'COM3'
serialBaud = 921600
dataNumBytes = 4
numData = 3
rawData = bytearray(numData * dataNumBytes)
# Connect to serial port
print('Trying to connect to ' + str(serialPort) +
' at ' + str(serialBaud) + ' BAUD.')
try:
s = serial.Serial(serialPort, serialBaud, timeout=4)
print('Connected!')
except:
print("Failed to connect with " + str(serialPort) +
' at ' + str(serialBaud) + ' BAUD.')
s.reset_input_buffer() # flush input buffer
while (True):
time.sleep(0.1)
s.readinto(rawData)
print(rawData)
终端输出:
bytearray(b'r u?\xb78\x0c\xbe\x1dN\x82>')
bytearray(b'@cu?\xb78\x0c\xbe0\xa7\x82>')
bytearray(b'\xca\x8fu?\x03\x9d\r\xbeno\x81>')
bytearray(b'@cu?\xb78\x0c\xbeno\x81>')
bytearray(b'\x0e\xa6u?\xb78\x0c\xbe\n\xf5\x81>')
bytearray(b'\x0e\xa6u?\xca\x91\x0c\xbe\n\xf5\x81>')
bytearray(b'\x98\xd2u?\xf0C\r\xbe\x81\xc8\x81>')
bytearray(b'\xca\x8fu?\x03\x9d\r\xbe0\xa7\x82>')
bytearray(b'\xca\x8fu?\xb78\x0c\xbe\xb9\xd3\x82>')
bytearray(b'@cu?\xb78\x0c\xbe\x1dN\x82>')
bytearray(b'@cu?\xb78\x0c\xbe\x1dN\x82>')
bytearray(b'\xfcLu?\xdd\xea\x0c\xbe\x94!\x82>')
好的。显然,数据输出是正确的,并且一切正常。我对12字节数据的理解是错误的。这是读取上面显示的示例的第一行的示例:
>>> from struct import *
>>> data = bytearray(b'r u?\xb78\x0c\xbe\x1dN\x82>') # define 12-byte data
>>> unpack('f', data[0:4]) # unpack 1st floating value
(0.9575263261795044,)
>>> unpack('f', data[4:8]) # unpack 2nd floating value
(-0.13693509995937347,)
>>> unpack('f', data[8:12]) # unpack 3rd floating value
(0.25450220704078674,)