Serial port operation can be used in the debugging process of daily embedded devices, and it is very convenient. The more troublesome should be the hexadecimal reception processing.
The serial library is used to operate the serial port in Python. The use process of serial is similar to the usual one, which is also open, close, read, write
1. Open the serial port
Generally, it is to set the port and baud rate.
When you use serial.Serial to create an entity, you will open the serial port, then you can use is_open to determine whether the serial port is open normally.
def DOpenPort(portx, bps, timeout):
try:
# 打开串口，并得到串口对象
ser = serial.Serial(portx, bps, timeout=timeout)
# 判断是否打开成功
if(False == ser.is_open):
ser = -1
except Exception as e:
print("---异常---：", e)
return ser
2. Close the serial port
Use ser.close to close the serial port
def DColsePort(ser):
uart.fdstate = -1
ser.close()
3. Write data
The data is written using the ser.write interface. If writing hexadecimal data, use bytearray to define, such aswritebuf = bytearray([0x55, 0xaa, 0x00, 0x01, 0x00, 0x00])
def DWritePort(ser, data):
result = ser.write(data) # 写数据
logging.info(ser)
logging.info("Write %s(%d)" % (data.hex(), result))
return result
4. Read the data
Read data using ser.read interface, generally use in_waiting to determine whether there is data, and then start reading
# 十六进制显示
def hexShow(argv):
try:
result = ''
hLen = len(argv)
for i in range(hLen):
hvol = argv[i]
hhex = '%02x' % hvol
result += hhex+' '
logging.info('Led Read:%s', result)
return result
except Exception as e:
print("---异常---：", e)
def DReadPort(ser):
# 循环接收数据，此为死循环，可用线程实现
readstr = ""
if ser.in_waiting:
readbuf = ser.read(ser.in_waiting)
if readbuf[0] == 0x55 and readbuf[1] == 0xaa:
readstr = readbuf
else:
readstr = readstr + readbuf
hexShow(readstr)
5. Examples
Here is an example to illustrate our actual use.
Generally, a process will be created separately to receive the data, and then the logic will be processed with the tag bit or semaphore.
import serial # 导入模块
import threading
import time
import logging
import sys
class UartInfo(object):
def __init__(self, fd, count, fail):
self.fd = fd
self.count = count # 测试次数
self.fail = fail # 失败次数
response = False
image_addr = 0x00
image_crc = 0x00
version = 0
write_event = threading.Event()
uart = UartInfo(-1, 0, 0)
def logging_init():
logging.basicConfig(# filename="test.log", # 指定输出的文件
level=logging.DEBUG,
format='%(asctime)s - %(filename)s[line:%(lineno)d] - %(levelname)s: %(message)s')
return True
# 十六进制显示
def hexShow(argv):
try:
result = ''
hLen = len(argv)
for i in range(hLen):
hvol = argv[i]
hhex = '%02x' % hvol
result += hhex+' '
logging.info('Led Read:%s', result)
return result
except Exception as e:
print("---异常---：", e)
def crc_sum(data, data_len):
crc = 0
i = 0
while(i < data_len):
crc += data[i]
i += 1
return crc & 0x00FF
def crc_sum_u32(data, data_len):
crc = 0
i = 0
while(i < data_len):
crc += data[i]
i += 1
return crc
# 打开串口
def DOpenPort(portx, bps, timeout):
try:
# 打开串口，并得到串口对象
ser = serial.Serial(portx, bps, timeout=timeout)
# 判断是否打开成功
if(False == ser.is_open):
ser = -1
except Exception as e:
print("---异常---：", e)
return ser
# 关闭串口
def DColsePort(ser):
uart.fdstate = -1
ser.close()
# 写数据
def DWritePort(ser, data):
result = ser.write(data) # 写数据
logging.info(ser)
logging.info("Led Write %s(%d)" % (data.hex(), result))
return result
# 读数据
def ReadData_Thread(ser):
# 循环接收数据，此为死循环，可用线程实现
readstr = ""
while(-1 != ser):
if ser.in_waiting:
try: # 如果读取的不是十六进制数据--
readbuf = ser.read(ser.in_waiting)
if readbuf[0] == 0x55 and readbuf[1] == 0xaa:
readstr = readbuf
else:
readstr = readstr + readbuf
hexShow(readstr)
if (readstr[3] == 0x01) and (len(readstr) > 10):
uart.version = readstr[16]
uart.response = True
uart.write_event.set()
elif (readstr[3] == 0x21) and (readstr[4] == 0x00) and (readstr[5] == 0x00):
uart.response = True
uart.write_event.set()
elif (readstr[3] == 0x22) and (len(readstr) > 10):
uart.image_addr = (readstr[6] << 24 & 0xFF000000)
uart.image_addr += (readstr[7] << 16 & 0x00FF0000)
uart.image_addr += (readstr[8] << 8 & 0x0000FF00)
uart.image_addr += (readstr[9] << 0 & 0x000000FF)
uart.response = True
uart.write_event.set()
elif (readstr[3] == 0x23) and (len(readstr) > 25):
uart.response = True
uart.write_event.set()
except: # --则将其作为字符串读取
readbuf = ser.read(ser.in_waiting)
hexShow(readbuf)
def GetVersion(ser):
print("GetVersion")
writebuf = bytearray([0x55, 0xaa, 0x00, 0x01, 0x00, 0x00])
# crc
writebuf.append(crc_sum(writebuf, len(writebuf)))
DWritePort(ser, writebuf)
logging.info("take")
uart.response = False
uart.write_event.clear()
uart.write_event.wait(timeout=3)
uart.write_event.clear()
logging.info("give")
if uart.response == False:
logging.info("fail")
return False
else:
return True
# 测试任务
def Test_Thread(ser):
while (-1 != ser):
uart.response = False
uart.image_addr = 0x00
uart.image_crc = 0x00
uart.version = 0
logging.info("count:%d", uart.count)
logging.info("fail:%d", uart.fail)
print("count", uart.count)
print("fail", uart.fail)
if GetVersion(ser):
logging.info(uart.version)
if uart.version == 0x37:
otafile = "./UartV108.bin"
else:
otafile = "./UartV107.bin"
else:
uart.fail += 1
uart.count += 1
continue
print("ota:", otafile)
logging.info("ota:%s", otafile)
time.sleep(2)
uart.count += 1
time.sleep(5)
def TestStop(ser):
DColsePort(uart.fd) # 关闭串口
if __name__ == "__main__":
if 2 != len(sys.argv):
print("please enter COM")
exit()
else:
uart.tty = sys.argv[1]
logging_init()
uart.fd = DOpenPort(uart.tty, 115200, None)
if(uart.fd != -1): # 判断串口是否成功打开
threading.Thread(target=Test_Thread, args=(uart.fd,)).start()
threading.Thread(target=ReadData_Thread, args=(uart.fd,)).start()
