Question

我正在尝试通过C程序读取NI USB-6211的电压输入。为此，我尝试使用已安装程序附带的一些示例程序，但无济于事。我看过文档，但说实话，它根本没什么帮助。

这是我改编的代码。（它有一些错误检入并要求输入......）

/*********************************************************************
*
* ANSI C Example program:
*    Acq-IntClk.c
*
* Example Category:
*    AI
*
* Description:
*    This example demonstrates how to acquire a finite amount of data
*    using the DAQ device's internal clock.
*
* Instructions for Running:
*    1. Select the physical channel to correspond to where your
*       signal is input on the DAQ device.
*    2. Enter the minimum and maximum voltages.
*    Note: For better accuracy try to match the input range to the
*          expected voltage level of the measured signal.
*    3. Select the number of samples to acquire.
*    4. Set the rate of the acquisition.
*    Note: The rate should be AT LEAST twice as fast as the maximum
*          frequency component of the signal being acquired.
*
* Steps:
*    1. Create a task.
*    2. Create an analog input voltage channel.
*    3. Set the rate for the sample clock. Additionally, define the
*       sample mode to be finite and set the number of samples to be
*       acquired per channel.
*    4. Call the Start function to start the acquisition.
*    5. Read all of the waveform data.
*    6. Call the Clear Task function to clear the task.
*    7. Display an error if any.
*
* I/O Connections Overview:
*    Make sure your signal input terminal matches the Physical
*    Channel I/O Control. For further connection information, refer
*    to your hardware reference manual.
*
*********************************************************************/

#include <stdio.h>
#include <NIDAQmx.h>
#include <string.h>

#define DAQmxErrChk(functionCall) if( DAQmxFailed(error=(functionCall)) ) goto Error; else

int main(void)
{
    int32       error=0;
    int32       amount; 
    int32       i;
    TaskHandle  taskHandle=0;
    int32       read;
    float64     data[1000];
    char        errBuff[2048]={'\0'};
    char        c = 64;

    /*********************************************/
    // DAQmx Configure Code
    /*********************************************/

    printf("Please enter the amount of voltage checks you wish to run.\n");
    //scanf("%d", &amount);

    while(scanf("%d%c", &amount, &c) !=2)
    {
        getchar();
        puts("Please enter a number.");
    }
    for (i = 0; i < amount; i++)
    {
        DAQmxErrChk (DAQmxCreateTask("",&taskHandle));
        DAQmxErrChk (DAQmxCreateAIVoltageChan(taskHandle,"Dev1/ai0","",DAQmx_Val_Cfg_Default,1.0,10.0,DAQmx_Val_Volts,NULL));
        DAQmxErrChk (DAQmxCfgSampClkTiming(taskHandle,"",10000.0,DAQmx_Val_Rising,DAQmx_Val_FiniteSamps,1000));

        /*********************************************/
        // DAQmx Start Code
        /*********************************************/
        DAQmxErrChk (DAQmxStartTask(taskHandle));

        /*********************************************/
        // DAQmx Read Code
        /*********************************************/

        DAQmxErrChk (DAQmxReadAnalogF64(taskHandle,1000,10.0,DAQmx_Val_GroupByChannel,data,1000,&read,NULL));

        printf("Acquired %d points\n",read);


Error:
        if( DAQmxFailed(error) )
            DAQmxGetExtendedErrorInfo(errBuff,2048);
        if( taskHandle!=0 )
        {
            /*********************************************/
            // DAQmx Stop Code
            /*********************************************/
            DAQmxStopTask(taskHandle);
            DAQmxClearTask(taskHandle);
            printf("Updating... ");
        }
    }

    if(i=amount)
    {
        printf("End of Program, press the Enter key to quit\n");
        getchar();      
        if( DAQmxFailed(error) )                
            printf("DAQmx Error: %s\n",errBuff);
    }       
    return 0;
}

此时所有代码正在打印数字1000我也问了多少次。我很确定这个代码来自float64 data[1000];。有没有人知道如何获得直接电压读数？即使它只是一长串没有格式化的数字（我可以想出来）。

由于

Answer 1

显示的1000号码来自您对DAQmxReadAnalogF64()的调用中的第二个和第七个参数。第二个参数说明您要采用的每个通道的样本数。 sevent参数（&read）告诉它在哪里存储实际采用每个通道的样本数的结果。所以你要求1000并得到1000。

当您的程序没有打印出已读入的数据时。对DAQmxReadAnalogF64()的调用执行数据采集并将其存储在第五个参数中指定的数组中（在您的情况下{{1} }}）。

在通话结束后，您可以使用以下内容打印出电压：

data

虽然这显然会打印出所有可能不是你想要的1000个值。

如果您要编写NI库的代码，那么您应该查看NI-DAQmx C参考帮助以获得有关函数及其参数的说明。他们有很多手册，很容易错过那个。这些例子通常也很容易适应。

NI USB 6211读取模拟电压输入

1 个答案: