通過RS232串口從條形碼掃描器讀取異步數據

Question

我有一個條形碼閱讀器，它通過RS232串口連接到PC。 我正在編寫一個C ++代碼來向條形碼掃描器發送命令並將響應返回給PC。 目前程序可以正確地向設備發送數據，但是無法讀取條形碼掃描器的響應。 在這種情況下，一旦我們向條形碼閱讀器發送命令，它將以肯定或否定確認回復。

e.g:- Send BEEP command.
 1. Host(PC) send a BEEP command to barcode scanner
 2. Barcode scanner make a beep sound and send the acknowledgement back
    to host (PC)
 3. Host (PC) read the acknowledgement

在下面的代碼中，前兩步正常工作，但我無法正確編寫第三個。 請有人幫我糾正我的源代碼，以異步方式讀取條形碼掃描器的響應。

main.cpp中

#include <iostream>
extern "C"
{
    #include <stdlib.h>
    #include <stdio.h>
    #include <unistd.h>
}
#include "DeviceRS232.h"
#include "Message.h"


int main()
{
    unsigned char recvBuffer[257];
    unsigned char ledOn[] = {0x05, 0xE7, 0x04, 0x00, 0x0D, 0x00};
    unsigned char SSIBuffer[] = {0x00, 0xC6, 0x04, 0x08, 0x11, 0xEE, 0x01};
    unsigned char requestRevision[] = {0x00, 0x04, 0xA3, 0x04, 0x00};
    unsigned char sendBeep[] = {0x00, 0xE6, 0x04, 0x00, 0x05};

    Message beepCommand(sendBeep, sizeof(sendBeep)/sizeof(sendBeep[0]));

    std::cout << "*********************************************************" << std::endl << std::endl;
    DeviceRS232 dev_rs232;
    dev_rs232.setDefaultAttributes();
    dev_rs232.openSerialPort();


    // Send BEEP command several times.
    std::cout << "---Start sending beep---" << std::endl;
    for(int x=0; x<1; x++)
    {
        int sizeSent = dev_rs232.sendDataBuffer(beepCommand.getCommandData(), beepCommand.getLen());
        if( sizeSent > 0)
        {
            std::cout << "Data sent: " <<  sizeSent << std::endl;
        }

        memset(recvBuffer, 0, sizeof(recvBuffer));
        int recvSize = dev_rs232.receiveDataBuffer(recvBuffer, sizeof(recvBuffer));
        std::cout << "Date Received, Data: " <<  recvBuffer << " Size: " << recvSize << std::endl;
        sleep(2);
        /**
        while(true)
        {
            memset(recvBuffer, 0, sizeof(recvBuffer));
            int recvSize = dev_rs232.receiveDataBuffer(recvBuffer, sizeof(recvBuffer));
            if(recvSize > 0)
                std::cout << "Date Received, Data: " <<  recvBuffer << " Size: " << recvSize << std::endl;
            sleep(2);
        }*/
    }
    std::cout << "---End sending beep-----\n" << std::endl;


    dev_rs232.closeSerialPort();
    std::cout << "*********************************************************" << std::endl;


    return 0;
}

Message.h

#ifndef MESSAGE_H
#define MESSAGE_H

#include <iostream>
#include <string>
#include <numeric>
extern "C"
{
    #include <stdlib.h>
    #include <stdio.h>
    #include <unistd.h>
}

class Message
{
    public:
        Message();              //  default constructor
        virtual ~Message();     //  destructor


        Message(const std::basic_string<unsigned char> msg) : commandMsg(msg)
        {
            printf("msg[0]:%x\n", msg[4]);
            std::cout << "length: " << commandMsg.length() << std::endl;

            //commandMsg[0] = commandMsg.length();
            appendChecksum();
        };

        Message(const unsigned char *msg, int msglen) : commandMsg(msg, msglen)
        {
            commandMsg[0] = commandMsg.length();
            appendChecksum();
        };

        const unsigned char *getCommandData() const
        {
            return commandMsg.c_str();
        }

        int getLen() const
        {
            return commandMsg.length();
        }


    protected:
    private:
        int appendChecksum();
        std::basic_string<unsigned char> commandMsg;
};

#endif // MESSAGE_H

Message.cpp

#include "Message.h"

Message::Message()
{
    //ctor
}

Message::~Message()
{
    //dtor
}

int Message::appendChecksum()
{
    int sum = -std::accumulate(commandMsg.begin(), commandMsg.end(), 0);

    commandMsg.push_back(0xFF & (sum >> 8));
    commandMsg.push_back(0xFF & sum);
}

DeviceRS232.h

#ifndef DEVICERS232_H
#define DEVICERS232_H

extern "C"
{
#include <stdio.h>
#include <string.h>
#include <termios.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <limits.h>
#include <stdlib.h>
}

#include <string>

#define MAX_SERIAL_PORT_NO  30



class DeviceRS232
{
    public:
        DeviceRS232();
        virtual ~DeviceRS232();

        int fdRS232;                    //  file descriptor for the serial port

        void setSerialPort(std::string sp);
        void setBaudRate(long baud);
        void setDataBits(int dataBit);
        void setStopBits(int stopBit);
        void setNumberOfParityBits(int nparityBits);
        void setDefaultAttributes();
        long getBaudRate();
        std::string getSerialPort();
        int openSerialPort();
        int readUserConfiguration();
        int sendDataBuffer(const unsigned char *dataBuffer, size_t bufferSize);
        int receiveDataBuffer(unsigned char *dataBuffer, size_t bufferSize);
        void closeSerialPort();


    protected:
        std::string serialPort;         //  Serial port like /dev/ttyS0
        long baudRate;                  //  Scanner baud rate
        int dataBits;                   //  data bits
        int stopBits;                   //  stop bits
        int numberOfParityBits;         //  number of parity bits
        termios oldSerialPortSetting;   //  Current values of termios structure for /dev/ttyS0
        termios newSerialPortSetting;   //  new termios attributes for /dev/ttyS0


    private:
};

#endif // DEVICERS232_H

DeviceRS232.cpp

#include "DeviceRS232.h"

DeviceRS232::DeviceRS232()
{
    //ctor
}

DeviceRS232::~DeviceRS232()
{
    //dtor
}

void DeviceRS232::setSerialPort(std::string sp)
{
    serialPort = sp;
}

void DeviceRS232::setBaudRate(long baud)
{
    baudRate = baud;
}

void DeviceRS232::setDataBits(int dataBit)
{
    dataBits = dataBit;
}

void DeviceRS232::setStopBits(int stopBit)
{
    stopBits = stopBit;
}

void DeviceRS232::setNumberOfParityBits(int nparityBits)
{
    numberOfParityBits = nparityBits;
}

void DeviceRS232::setDefaultAttributes()
{
    std::string sp = "/dev/ttyS0";
    long baud = 9600;
    int dataBit = 1;
    int stopBit = 1;
    int nparityBits = 0;

    setSerialPort(sp);
    setBaudRate(baud);
    setDataBits(dataBit);
    setStopBits(stopBit);
    setNumberOfParityBits(nparityBits);
}

long DeviceRS232::getBaudRate()
{
    return baudRate;
}

std::string DeviceRS232::getSerialPort()
{
    return serialPort;
}

int DeviceRS232::openSerialPort()
{
    int fd, baudr, status, portStatus;
    setDefaultAttributes();

    switch(getBaudRate())
    {
        case      50 : baudr = B50;
                       break;
        case      75 : baudr = B75;
                       break;
        case     110 : baudr = B110;
                       break;
        case     134 : baudr = B134;
                       break;
        case     150 : baudr = B150;
                       break;
        case     200 : baudr = B200;
                       break;
        case     300 : baudr = B300;
                       break;
        case     600 : baudr = B600;
                       break;
        case    1200 : baudr = B1200;
                       break;
        case    1800 : baudr = B1800;
                       break;
        case    2400 : baudr = B2400;
                       break;
        case    4800 : baudr = B4800;
                       break;
        case    9600 : baudr = B9600;
                       break;
        case   19200 : baudr = B19200;
                       break;
        case   38400 : baudr = B38400;
                       break;
        case   57600 : baudr = B57600;
                       break;
        case  115200 : baudr = B115200;
                       break;
        case  230400 : baudr = B230400;
                       break;
        case  460800 : baudr = B460800;
                       break;
        case  500000 : baudr = B500000;
                       break;
        case  576000 : baudr = B576000;
                       break;
        case  921600 : baudr = B921600;
                       break;
        case 1000000 : baudr = B1000000;
                       break;
        default      : printf("invalid baudrate\n");
                       return(1);
                       break;
    }

    //  Open serial port
    fd = open(getSerialPort().c_str(),  O_RDWR | O_NOCTTY | O_NDELAY);
    if(fd == -1)
    {
        printf("Unable to open serial port...\n");
        perror(getSerialPort().c_str());
        return 1;
    }

    fdRS232 = fd;

    fcntl(fdRS232, F_SETFL, FNDELAY);
    status = tcgetattr(fdRS232, &oldSerialPortSetting);
    if(status == -1)
    {
        close(fdRS232);
        printf("Unable to get serial port attributes...\n");
        return 1;
    }

    memset(&newSerialPortSetting, 0, sizeof(newSerialPortSetting));
    newSerialPortSetting.c_cflag = baudr | CS8 | CLOCAL | CREAD; //
    newSerialPortSetting.c_iflag = IGNPAR;
    newSerialPortSetting.c_oflag = 0;
    newSerialPortSetting.c_lflag = 0;
    newSerialPortSetting.c_cc[VMIN] = 0;
    newSerialPortSetting.c_cc[VTIME] = 0;

    status = tcsetattr(fdRS232, TCSANOW, &newSerialPortSetting);
    if(status==-1)
    {
        close(fdRS232);
        perror("unable to adjust portsettings ");
        return 1;
    }

    //  Get the status of opened serial port
    if(ioctl(fdRS232, TIOCMGET, &portStatus) == -1)
    {
        perror("Unable to get port status");
        return 1;
    }

    //  Tern on DTR and RTS
    portStatus |= TIOCM_DTR;
    portStatus |= TIOCM_RTS;

    //  Set the status of the port with new DTR, RTS values
    if(ioctl(fdRS232, TIOCMSET, &portStatus) == -1)
    {
        perror("Unable to set port status...");
        return 1;
    }

  return 0;
}

int DeviceRS232::sendDataBuffer(const unsigned char *dataBuffer, size_t bufferSize)
{
    return write(fdRS232, dataBuffer, bufferSize);
}

int DeviceRS232::receiveDataBuffer(unsigned char *dataBuffer, size_t bufferSize)
{
    /**int recvSize = 0;
    recvSize = read(fdRS232, dataBuffer, bufferSize);
    return recvSize;*/

    unsigned char recvBuffer[255];
    unsigned char *ptrChar;
    int nBytes;

    ptrChar = recvBuffer;
    memset(recvBuffer, 0x00, sizeof(recvBuffer));
    while((nBytes = read(fdRS232, ptrChar, recvBuffer+sizeof(recvBuffer) - ptrChar -1)) > 0)
    {
        ptrChar += nBytes;
        //printf("while - %d\n", nBytes);
    }

    //printf("recvBuffer : %x\n", recvBuffer[0]);
    //printf("recvBuffer : %x\n", recvBuffer[1]);
    //printf("recvBuffer : %x\n", recvBuffer[2]);
    //printf("recvBuffer : %x\n", recvBuffer[3]);
    //printf("recvBuffer : %x\n", recvBuffer[4]);
    dataBuffer = recvBuffer;

    return nBytes;
}

void DeviceRS232::closeSerialPort()
{
    int portStatus;

    if(ioctl(fdRS232, TIOCMGET, &portStatus) == -1)
    {
        perror("Unable to get the port status");
    }

    //  Tern off DTR and RTS
    portStatus &= ~TIOCM_DTR;
    portStatus &= ~TIOCM_RTS;

    //  Set the status of the port with new DTR, RTS values
    if(ioctl(fdRS232, TIOCMSET, &portStatus) == -1)
    {
        perror("Unable to set port status...");
    }

    close(fdRS232);
}

我的錯誤方法是int DeviceRS232::receiveDataBuffer(unsigned char *dataBuffer, size_t bufferSize)

以下是控制台輸出：

*********************************************************

---Start sending beep---
Data sent: 7
Date Received, Data:  Size: 0
---End sending beep-----

*********************************************************

Process returned 0 (0x0)   execution time : 2.004 s
Press ENTER to continue.

Answer 1

正如其他人所指出的，一個可疑區域是您要發送的字節數。 條形碼閱讀器可能只需要命令中的字節數而不是更多，而不是總是發送257個字節。

此外，您的代碼還有許多重復操作，用於計算消息末尾的校驗和。 這表明課程將有助於簡化設計。 那么，這是一個用於此目的的Message類：

#include <vector>
#include <numeric>
#include <string>

class Message 
{
public:
    Message(const std::basic_string<unsigned char> msg) : mymsg(msg) { 
        mymsg[0] = mymsg.length(); appendChecksum(); };
    Message(const unsigned char *msg, int msglen) : mymsg(msg, msglen) { 
        mymsg[0] = mymsg.length(); appendChecksum(); };
    const unsigned char *getData() const { return mymsg.c_str(); }
    size_t getLen() const { return mymsg.length(); }

private:
        int appendChecksum();
        std::basic_string<unsigned char> mymsg;
};


int Message::appendChecksum()
{
    int sum = -std::accumulate(mymsg.begin(), mymsg.end(), 0);
    mymsg.push_back(0xff & (sum >> 8));
    mymsg.push_back(0xff & sum);
    return sum;
}

現在你的內main套路，就可以消除的代碼幾十行，並利用這些來代替（如果你使用C ++ 11）：

    Message setparams{{0x00, 0xc6, 0x04, 0x08, 0x11, 0xee, 0x01}};
    Message beep{{0x00, 0xe6, 0x04, 0x00, 0x05}};
    Message getrevision{{0x00, 0xA3, 0x04, 0x00}};
    Message ledOn{{0x00, 0xe7, 0x04, 0x00, 0x0d, 0x00}};

如果你不使用C ++ 11（這將是一個恥辱！）你可以使用這個稍微不那么干凈的風格：

unsigned char parms[] = {0x00, 0xc6, 0x04, 0x08, 0x11, 0xee, 0x01};
Message setparams(parms,sizeof(parms)/sizeof(parms[0]));

請注意，第一個字節設置為零而不是長度。 這樣做是因為構造函數在計算和附加校驗和之前自動計算並設置該字節中的正確長度。 當然，還有其他方法可以做到這一點，但我會留給你。

最后，通過循環，您現在可以使用此行：

int sizeSent = dev_rs232.sendDataBuffer(beep.getData(), beep.getLen());

這可能會或可能不會實際解決問題，但它將幫助您開始一個更清潔的程序。

還有一些風格和設計建議：

1. 擺脫using namespace std的習慣
2. 使用iostream而不是printf
3. 而不是在創建設備后立即調用setDefaultAttributes() ，讓構造函數設置sane默認值
4. 消除接收緩沖區大小的“幻數”，例如4096。 相反，使用命名static const 。 它將使程序更易理解和可維護。
5. 考慮使用現有的庫，如boost::asio而不是自己滾動

祝好運！

編輯：基於你敏銳（並且正確！）觀察到Message構造函數在提供普通的unsigned char *時無法正常工作，我添加了第二個構造函數並修改了代碼的非C ++ 11版本。 很抱歉給您帶來不便，感謝您保持誠實。

Answer 2

/**
 * Receive responses from the decoder
 */
int DeviceRS232::receiveDecodedData(unsigned char *dataBuffer, size_t bufferSize)
{
    unsigned char recvBuffer[251];
    unsigned char *ptrChar;
    int nBytes, portStatus;
    int inputBufSize = 0;

    ChangeCTS(fdRS232, 0);
    ChangeRTS(fdRS232, 0);

    while(inputBufSize <= 0)
    {
        ioctl(fdRS232, FIONREAD, &inputBufSize);
        usleep(1);
    }


    if(inputBufSize > 0)
    {
        int decodePacketLen = 0;
        //unsigned char
        memset(recvBuffer, 0x00, sizeof(recvBuffer));
        nBytes = 0;

        //usleep(100000);
        while(nBytes < ((int)recvBuffer[0] + 2))
        {
            int index = 0;
            int recvDataLen = 0;
            if(nBytes != 0)
                index = nBytes - 1;

            recvDataLen = read(fdRS232, &recvBuffer[index], 251);
            if(recvDataLen < 0)
            {
                std::cout << "[INFO@DeviceRS232::receiveDecodedData]File read error: " << strerror(errno) << std::endl;
                //sleep(1);
            }

            nBytes += recvDataLen;
            if(nBytes == ((int)recvBuffer[0] + 2))
                break;

        }

        if(recvBuffer[1] == DECODE_DATA)
            sendCommandToDecoder(OPCODE_ACK);

        std::cout << "[INFO @ DeviceRS232::receiveDecodedData]Data Lenght (without CheckSum) : " << (int)recvBuffer[0] << std::endl;

        for(int i=0; i<nBytes; i++)
        {
            std::cout << "recvBuffer[" << i << "]: ";
            printf("%x\n", recvBuffer[i]);
        }
        std::cout << "-----------------------------------" << std::endl;

        ChangeRTS(fdRS232, 1);
        ChangeCTS(fdRS232, 1);
        //sleep(1);
    }

    //strcpy((char *)dataBuffer, (char *)recvBuffer);
    memcpy((char *)dataBuffer, recvBuffer, sizeof(recvBuffer)/sizeof(recvBuffer[0]));
    inputBufSize = 0;

    return nBytes;

}


/**
 * Send commands to the decoder.
 */
int DeviceRS232::sendCommandToDecoder(unsigned int opCode)
{
    unsigned char *commandBuffer;
    int commandLength;

    switch(opCode)
    {
    case OPCODE_ACK:
        {
            unsigned char ackString[] = {0x00, 0xD0, 0x04, 0x00};
            commandLength = sizeof(ackString);
            commandBuffer = ackString;
        }
        break;
    case OPCODE_PARAM_SEND:
        {
            unsigned char paramSendString[] = {0x00, 0xC6, 0x04, 0x08, 0x00, 0xEE, 0x01};
            commandLength = sizeof(paramSendString);
            commandBuffer = paramSendString;
        }
        break;
    default:
        break;
    }

    Message msgCommand(commandBuffer, commandLength);

    return sendDataBuffer(msgCommand.getCommandData(), msgCommand.getLen());
}

DeviceRS232.h頭文件中定義的必需常量。