两个函数串行发送不同波特率数据的问题？ [英] problems with two functions for sending data at different baudrate serially?

问题描述

//Serial Port communication in Windows  for test purpose!!//
#include <windows.h>
#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#include <dos.h>


int main()
{
    int _kbhit();
    int _getch();


    // Defining hexadecimal bytes to be sent a 200 bps//
    unsigned int bytes_to_send[1];
    bytes_to_send[0] = 0xF0; /* 11110000b */

     // Defining hexadecimal bytes to be sent a 10400 bps//
    unsigned int databytes_send[5];
    databytes_send[0] = 0x81;
    databytes_send[1] = 0x11;
    databytes_send[2] = 0xF1;
    databytes_send[3] = 0x11;
    databytes_send[4] = 0x04;

    int GetPressedKey()
    {
        int ret = 0;
        if (_kbhit())
        {
            ret = _getch();
        }
        return ret;
    }

    // Declare variables and structures//
    HANDLE hSerial;
    DCB dcbSerialParams = {0};
    COMMTIMEOUTS timeouts = {0};

    // Open the available serial port number//
    fprintf(stderr, "Opening serial port...");
    hSerial = CreateFile(
                "COM4", GENERIC_READ|GENERIC_WRITE, 0, NULL,
                OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL );
    if (hSerial == INVALID_HANDLE_VALUE)
    {
        fprintf(stderr, "Error\n");
        return 1;
    }
    else
        fprintf(stderr, "OK\n");

    // Set device parameters (200 baud, 1 start bit,
    // 1 stop bit, no parity)
    dcbSerialParams.DCBlength = sizeof(dcbSerialParams);
    if (GetCommState(hSerial, &dcbSerialParams) == 0)
    {
        fprintf(stderr, "Error getting device state\n");
        CloseHandle(hSerial);
        return 1;
    }

    while(1)
    {

    // Set baudrate to send bytes at 200 bps//
    dcbSerialParams.BaudRate = 200;
    dcbSerialParams.ByteSize = 8;
    dcbSerialParams.StopBits = ONESTOPBIT;
    dcbSerialParams.Parity = NOPARITY;
    if(SetCommState(hSerial, &dcbSerialParams) == 0)
    {
        fprintf(stderr, "Error setting device parameters\n");
        CloseHandle(hSerial);
        return 1;
    }

    // Set COM port timeout settings//
    timeouts.ReadIntervalTimeout = 50;
    timeouts.ReadTotalTimeoutConstant = 50;
    timeouts.ReadTotalTimeoutMultiplier = 10;
    timeouts.WriteTotalTimeoutConstant = 50;
    timeouts.WriteTotalTimeoutMultiplier = 10;
    if(SetCommTimeouts(hSerial, &timeouts) == 0)
    {
        fprintf(stderr, "Error setting timeouts\n");
        CloseHandle(hSerial);
        return 1;
    }

    // Send specified text (remaining command line arguments)
    DWORD bytes_written = 0;
    fprintf(stderr, "sending bytes...\n");

        //Transmit slow initialization data
        if (!WriteFile(hSerial, bytes_to_send, 1, &bytes_written, NULL))

            break;

        fprintf(stderr, "%d bytes written\n", bytes_written);

        //check for key press event
        if (GetPressedKey())
            break;

        // Set baudrate to send bytes at 10400 bps//
        dcbSerialParams.BaudRate = 10400;
        dcbSerialParams.ByteSize = 8;
        dcbSerialParams.StopBits = ONESTOPBIT;
        dcbSerialParams.Parity = NOPARITY;
        if(SetCommState(hSerial, &dcbSerialParams) == 0)
        {
            fprintf(stderr, "Error setting device parameters\n");
            CloseHandle(hSerial);
            return 1;
        }

        // Set COM port timeout settings//
        timeouts.ReadIntervalTimeout = 50;
        timeouts.ReadTotalTimeoutConstant = 50;
        timeouts.ReadTotalTimeoutMultiplier = 10;
        timeouts.WriteTotalTimeoutConstant = 50;
        timeouts.WriteTotalTimeoutMultiplier = 10;
        if(SetCommTimeouts(hSerial, &timeouts) == 0)
        {
            fprintf(stderr, "Error setting timeouts\n");
            CloseHandle(hSerial);
            return 1;
        }

        //Transmit fast initialization data
        if (!WriteFile(hSerial, databytes_send, 5, &bytes_written, NULL))

            break;

        fprintf(stderr, "%d bytes written\n", bytes_written);

        //Check for key press event
        if (GetPressedKey())
            break;
    }

    DWORD bytes_written;

    CloseHandle(hSerial);

    if(!WriteFile(hSerial, bytes_written,5, &bytes_written, NULL))
    {
        fprintf(stderr, "End of transmission\n");
        CloseHandle(hSerial);

        return 1;
    }
    fprintf(stderr, "%d bytes written\n", bytes_written);



    // Close serial port
    fprintf(stderr, "Closing serial port...");
    if (CloseHandle(hSerial) == 0)
    {
        fprintf(stderr, "Error\n");
        return 1;
    }
    fprintf(stderr, "OK\n");

    // exit normally
    return 0;
}

推荐答案

vinod bv写道：

vinod b v wrote:

在200波特发送字节0xF0时我应该得到25ms低和25ms高方波，接下来我的5个数据字节应该在10400发送，但我无法在示波器中看到确切的波形。代码中有什么问题??

I am supposed to get 25ms low and 25ms high square wave upon sending byte 0xF0 at 200 baud, and next my 5 databytes should be sent at 10400, but i am not able to see the exact waveform in my oscilloscope. is there something wrong in the code??

你对这个范围有什么看法？

限制程序第一部分的讨论（200波特），应该有一个脉冲，如：

What do you see on the scope?
Limiting the discussion on the first part of your program (200 baud), there should be a single pulse, like:

______      _______________________________________________
      |_____|

是高 - >低转换，25毫秒低（起始位+4个零位）然后低 - >高转换（ 4个一位，停止位，最后线路保持高电平，空闲）。

参见：异步串行沟通 [ ^ ]。

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