Question

我正在尝试编写一个使用USB转串口转换器与串行接口通信的代码。我在Ubuntu 12.04操作系统上运行我的代码。我已经附加了设备，看起来它被系统识别，因为lsusb的输出给了我：

Bus 002 Device 003: ID 9710:7840 MosChip Semiconductor MCS7820/MCS7840 2/4 port serial adapter

和 dmesg 命令报告：

Tue Apr 18 15:22:07 2017] usb 2-2: new high-speed USB device number 3 using ehci_hcd
[Tue Apr 18 15:22:07 2017] usbcore: registered new interface driver usbserial
[Tue Apr 18 15:22:07 2017] USB Serial support registered for generic
[Tue Apr 18 15:22:07 2017] usbcore: registered new interface driver usbserial_generic
[Tue Apr 18 15:22:07 2017] usbserial: USB Serial Driver core
[Tue Apr 18 15:22:07 2017] USB Serial support registered for Moschip 7840/7820 USB Serial Driver*
[Tue Apr 18 15:22:07 2017] mos7840: 1.3.2:Moschip 7840/7820 USB Serial Driver
[Tue Apr 18 15:22:07 2017] mos7840 2-2:1.0: Moschip 7840/7820 USB Serial Driver converter detected
[Tue Apr 18 15:22:07 2017] usb 2-2: Moschip 7840/7820 USB Serial Driver converter now attached to ttyUSB0
[Tue Apr 18 15:22:07 2017] usb 2-2: Moschip 7840/7820 USB Serial Driver converter now attached to ttyUSB1
[Tue Apr 18 15:22:07 2017] usb 2-2: Moschip 7840/7820 USB Serial Driver converter now attached to ttyUSB2
[Tue Apr 18 15:22:07 2017] usb 2-2: Moschip 7840/7820 USB Serial Driver converter now attached to ttyUSB3
[Tue Apr 18 15:22:07 2017] usbcore: registered new interface driver mos7840

然而，当我尝试运行我的代码时，我没有从另一方得到预期的答案。我正在运行的代码在这里：

class RTSSerial(object):

    def __init__(self,serialID, baud):
        self.serialID = serialID
        self.baud = baud
        try:
            self.serDevice = serial.Serial(self.serialID, 
                                           baudrate = self.baud,
                                           parity = serial.PARITY_NONE,
                                           stopbits = serial.STOPBITS_ONE,
                                           bytesize = serial.EIGHTBITS)
            self.serDevice.flushInput()
            self.serDevice.flushOutput()
        except Exception as e:
            print 'Got the following exception: ', e

    def read(self):        
        try:
            inWaiting = self.serDevice.inWaiting()
        except:            
            if os.path.exists(self.serialID):
                self.serDevice = serial.Serial(self.serialID,self.baud)
            inWaiting = 0

        try:
            rec = ''
            if (inWaiting > 0):
                rec = self.serDevice.read(inWaiting)
                #Convert string message into list of integers        
            message = [ord(x) for x in rec]        
        except Exception as e:
            message = []
            print 'Got the following exception: ', e

        return message

    #Function to write to serial
    #message should be a list. Then the function converts it into a string
    def write(self, message):      
        try:
            #Convert message into string
            messageToSend = "".join(chr(x) for x in message)        
            errCode = self.serDevice.write(messageToSend)
        except Exception as e:
            errCode = 0
            print 'Got the following exception: ', e

        return errCode

ser = RTSSerial('/dev/ttyUSB0', 9600)    
mess = [0x7e, 0xa, 0x0, 0x0, 0x10, 0x0, 0x0, 0x0, 0x0, 0x4d, 0x8a]
ser.write(mess)
time.sleep(1)
reply = ser.read()

我希望得到一个回复：

0x7E 0x04 0x00 CRC1 CRC2

但我得到了：

0x7e 0xd 0xa 0x43 0x20 0x69 0x6e 0x74 0x65 0x72 0x70 0x3a 0x20 0x73 0x79 0x6e 0x74 0x61 0x78 0x20 0x65 0x72 0x72 0x6f 0x72 0x2e 0xd 0xa 0x2d 0x3e 0x20 0x3f 0x4d 0xd 0xa 0x43 0x20 0x69 0x6e 0x74 0x65 0x72 0x70 0x3a 0x20 0x74 0x6f 0x6b 0x65 0x6e 0x20 0x27 0x10 0x27 0x20 0x6e 0x6f 0x74 0x20 0x72 0x65 0x63 0x6f 0x67 0x6e 0x69 0x7a 0x65 0x64 0x2e 0xd 0xa 0x2d 0x3e 0x20

我在这里有什么东西吗？提前谢谢！

Answer 1

如果您以ASCII而非十六进制查看结果，则会得到：

~
C interp: syntax error.
-> ?M
C interp: token '' not recognized.
->

（引号中的标记是十六进制0x10，是您尝试发送的字符之一。）因此，您的串行接收工作正常 - 您只是没有得到预期的结果。看起来其他系统处于文本提示状态，并且不期望您发送的二进制数据包。可能需要首先发送一些命令才能使其进入正确的模式。

Python：与USB到串行转换器的串行通信失败

1 个答案: