Question

我想我必须使用MEX-File从Matlab到我的DAQ-Board以环路（40 kHz）输出数字脉冲，我有来自DAQ-Board供应商的一些API，但我真的不知道它们是否是有用。这是Mathworks网站上有关MEX-File和API的重要文档，这让我感到困惑。所以我在这里询问是否有人可以定位我或向我展示一个示例代码来实现这一点!!

Answer 1

我之前使用mex函数编写了一个小的winsock包，因为Matlab的tcpip存在发送大量数据（如图像）的问题。除了我学到的使用该软件包之外，我对mex函数知之甚少，甚至那是很久以前的事了。但是，这里是我以前的一些笔记和我编写的一个函数作为一个例子，希望对你有所帮助。

在编写任何mex函数之前，需要配置Matlab才能编译它们。您可以通过在matlab命令行中键入“mex -setup”并按照其提供的说明执行此操作。我将其配置为使用Visual Studio编译器（请注意，必须安装Visual Studio才能显示此选项）。

配置编译器后，通过在Matlab命令行中键入“mex filename.cpp”来编译mex函数。这会生成一个.mexw32文件（假设为32位），当您调用mex函数时，Matlab会使用该文件。

要编写mex函数本身，您可以编写一个m文件来声明它并提供注释以及带有实际实现的cpp文件。

举个例子，这是我写的一个m文件：

function sendColorImage( socketHandle, colorImage ) %#ok<*INUSD>
%SENDCOLORIMAGE Sends a color image over the given socket
%   This function sends a color image over the socket provided.  The image
%   is really just an MxNx3 matrix.  Note that this function sends the
%   image data in the order in which Matlab stores it (non-interlaced
%   column major order), which is different from most other languages.
%   This means the red values for every pixel will be sent first, then the
%   green values, then the blue values.  Furthermore, the scanlines read
%   from the top of the image to the bottom, starting at the left side of
%   the image.
%
%   socketHande - A handle to the socket over which the image should be
%   sent.  This handle is returned by the openSocket function when the
%   socket is first created.
%
%   colorImage - An MxNx3 matrix containing the image data.  This matrix
%   should be in the same format as a matrix loaded using Matlabs imread
%   function.
%
%   This is a mex function and is defined in its corresponding .cpp file.

这是相应的cpp文件。请注意，我只是编写了自己的消息格式，并使用了相应的C＃代码，将其从字节流中解析出来。

// Instruct the compiler to link with wsock32.lib (in case it isn't specified on the command line)
#pragma comment(lib,"wsock32.lib")

#include "mex.h"
#include <winsock2.h>
#include <cstdio>
#include "protocol.h"

// See the corresponding .m file for documentation on this mex function.
void mexFunction(int nlhs, mxArray* plhs[], int nrhs, const mxArray* prhs[]){

    char errorMessage[100];

    // Validate input and output arguments
    if(nlhs != 0)
        mexErrMsgTxt("There are no output arguments for this function.");
    if(nrhs != 2)
        mexErrMsgTxt("Must have 2 input parameters: the socket handle and the MxNx3 image matrix");
    if(!mxIsClass(prhs[0], "uint32"))
        mexErrMsgTxt("The first input parameter should be a uint32 containing the socket handle");
    if(!mxIsClass(prhs[1], "uint8") || mxGetNumberOfDimensions(prhs[1]) != 3 || mxGetDimensions(prhs[1])[2] != 3)
        mexErrMsgTxt("The 2nd input parameter should be an MxNx3 uint8 matrix containing the image");

    // Get the socket handle
    SOCKET socketHandle = (int)(mxGetPr(prhs[0])[0]);

    // Set up the header
    int frameWidth = mxGetDimensions(prhs[1])[1];
    int frameHeight = mxGetDimensions(prhs[1])[0];
    int header[3];
    header[0] = COLOR_IMAGE;
    header[1] = frameWidth;
    header[2] = frameHeight;

    // Send the header
    int bytesSent;
    int totalBytesSent = 0;
    while(totalBytesSent < 3*sizeof(int)){
        bytesSent = send(socketHandle, ((char*)header) + totalBytesSent, 3*sizeof(int) - totalBytesSent, 0);
        if(bytesSent == SOCKET_ERROR){
            sprintf(errorMessage, "Error sending image header over the socket: %d", WSAGetLastError());
            mexErrMsgTxt(errorMessage);
        }
        totalBytesSent += bytesSent;
    }

    // Send the image
    totalBytesSent = 0;
    int totalBytesToSend = frameWidth * frameHeight * 3;
    char* dataPointer = (char*)mxGetData(prhs[1]);
    while(totalBytesSent < totalBytesToSend){
        bytesSent = send(socketHandle, dataPointer + totalBytesSent, totalBytesToSend - totalBytesSent, 0);
        if(bytesSent == SOCKET_ERROR){
            sprintf(errorMessage, "Error sending image over the socket: %d", WSAGetLastError());
            mexErrMsgTxt(errorMessage);
        }
        totalBytesSent += bytesSent;
    }
}

MEX-File将脉冲输出到DAQ板

1 个答案: