在 python 中从各种 USB 设备读取和存储各种数据

output_file = open('hygro.txt', 'w') #create a file and allow you to write in it only. The name of this file is hygro.txt

ser = serial.Serial("/dev/tty.usbserial-A400DUTI", 9600) #load into a variable 'ser' the information about the usb you are listening. /dev/tty.usbserial.... is the port after plugging in the hygrometer, 9600 is for bauds, it can be diminished
count = 0
while 1:
    read_byte = ser.read(size=1)

    trad_hexa = int(read_byte_hexa , 16) #convert the hexadecimal into an int in purpose to compare it with another int
    trad_firstcrchar = int('3c' , 16) #convert the hexadecimal of the '<' into a int to compare it with the first byte    
    if (trad_hexa == trad_firstcrchar ): #compare the first byte with the '<'    
        read_byte = ser.read(size=1) #read the next byte (I am not sure if that really works)
        read_byte_hexa =binascii.hexlify(read_byte)# from now I am doing the same thing as before
        trad_hexa = int(read_byte_hexa , 16)
        trad_scdcrchar = int('63' , 16)
        print(trad_hexa, end='/')# this just show me if it gets in the condition
        print(trad_scdcrchar)    
        if (trad_hexa == trad_scdcrchar ):    
            read_byte = ser.read(size=1) #read the next byte
            read_byte_hexa =binascii.hexlify(read_byte)
            trad_hexa = int(read_byte_hexa , 16)
            trad_thirdcrchar = int('72' , 16)
            print(trad_hexa, end='///')
            print(trad_thirdcrchar)    
            if (trad_hexa == trad_thirdcrchar ):    
                read_byte = ser.read(size=1) #read the next byte
                read_byte_hexa =binascii.hexlify(read_byte)
                trad_hexa = int(read_byte_hexa , 16)
                trad_fourthcrchar = int('3e' , 16)
                print(trad_hexa, end='////')
                print(trad_fourthcrchar)    
                if (trad_hexa == trad_fourthcrchar ):    
                    print ('end of the line')

def parse_info_line(line):
    # implement to your own liking
    logical_channel, physical_probe, hardware_id, crc = [line[index:index+2] for index in (1, 3, 5, 19)]
    serialno = line[7:19]
    return physical_probe

def parse_value_line(line):
    channel, crc = [line[ind:ind+2] for ind in (1,7)]
    encoded_temp = line[3:7]
    return twos_comp(int(encoded_temp, 16), 16)/100.

def twos_comp(val, bits):
   """compute the 2's compliment of int value `val`"""
    if (val & (1 << (bits - 1))) != 0: # if sign bit is set e.g., 8bit: 128-255
        val = val - (1 << bits)        # compute negative value
    return val                         # return positive value as is

def listen_on_serial(ser):
    ser.readline() # do nothing with the first line: you have no idea when you start listening to the data broadcast from the sensor
    while True:
        line = ser.readline()
        try:
            first_char = line[0]
        except IndexError:  # got no data from sensor
            break
        else:
            if first_char == '@':  # begins a new sensor record
                in_record = True
            elif first_char == '$':
                in_record = False
            elif first_char == 'I':
                parse_info_line(line)
            elif first_char == 'V':
                print(parse_value_line(line))
            else:
                print("Unexpected character at the start of the line:\
{}".format(line))
            time.sleep(2)