Hi all
I can't get an analog reference trigger to work using the NI-DAQmx Base 3.0 C API. I am using a USB-6008 on Windows XP. I have an analog voltage source connected to AI0 that I want to use as a trigger, and then sample that same input. Please see code below. When compiled and run, this code yields the error "Value passed to the Task/Channels In control is invalid." when it gets to DAQmxBaseCfgAnlgEdgeRefTrig(). What string to I need to pass to this function to get it to trigger on AI0?
I have tried using other channel names in DAQmxBaseCfgAnlgEdgeRefTrig(), including "/Dev/ai0" (leading slash), all-caps versions, /Dev/PFI0 (just to see if it would run, not because I want to use PFI0 to trigger), and everything gives the same error. Help is much appreciated. Code below.
Thanks
Andrew
#include "NIDAQmxBase.h"
#include <stdio.h>
#include <time.h>
#define DAQmxErrChk(functionCall) { if( DAQmxFailed(error=(functionCall)) ) { goto Error; } }
int main(int argc, char *argv[])
{
// Task parameters
int32 error = 0;
TaskHandle taskHandle = 0;
char errBuff[2048]={'\0'};
int32 i,j;
time_t startTime;
bool32 done=0;
// Channel parameters
char chan[] = "Dev1/ai0";
float64 min = -1.0;//volts
float64 max = 4.0;//volts
// Timing parameters
char clockSource[] = "OnboardClock";
float64 sampleRate = 100.0; //per second
float64 triggerLevel = 2.0; //volts
int32 preTriggerSamples = sampleRate/2; // half a second's worth of samples
uInt64 numSamples = 2*preTriggerSamples; // total number of samples (includes pre-trigger)
// Data read parameters
#define bufferSize (uInt32)1000
float64 data[bufferSize * 2];
int32 pointsToRead = bufferSize;
int32 pointsRead;
float64 timeout = 10.0;
int32 totalRead = 0;
printf("Press Ctrl-C to exit\n");
DAQmxErrChk (DAQmxBaseCreateTask("",&taskHandle));
printf("Configuring AnalogInput Channel\n");
DAQmxErrChk (DAQmxBaseCreateAIVoltageChan(
taskHandle,
chan,
NULL, //name to give channel -- not supported by API
DAQmx_Val_Cfg_Default,
min,
max,
DAQmx_Val_Volts,
NULL
));
printf("Configuring Sample Clock\n");
DAQmxErrChk (DAQmxBaseCfgSampClkTiming(
taskHandle,
clockSource,
sampleRate,
DAQmx_Val_Rising,
DAQmx_Val_FiniteSamps,
numSamples//total number of samples to acquire
));
printf("Configuring Analog Reference Trigger\n");
DAQmxErrChk (DAQmxBaseCfgAnlgEdgeRefTrig (
taskHandle,
chan, //channel to trigger on
DAQmx_Val_FallingSlope, //edge to trigger on
triggerLevel,
preTriggerSamples
));
printf("Configuring input buffer\n");
DAQmxErrChk (DAQmxBaseCfgInputBuffer(taskHandle,2*numSamples)); //configure a buffer twice as large as we will need
// start monitoring
while( 1 ) {
printf("Monitoring...\n");
DAQmxErrChk (DAQmxBaseStartTask(taskHandle));
DAQmxErrChk (DAQmxBaseReadAnalogF64(
taskHandle,
pointsToRead,
timeout,
DAQmx_Val_GroupByScanNumber,
data,
bufferSize*2,
&pointsRead,
NULL
));
DAQmxErrChk (DAQmxBaseStopTask(taskHandle));
totalRead += pointsRead;
printf("Trigger\n");
}
printf("\nAcquired %d total samples.\n",totalRead);
Error:
if( DAQmxFailed(error) )
DAQmxBaseGetExtendedErrorInfo(errBuff,2048);
if(taskHandle != 0) {
DAQmxBaseStopTask (taskHandle);
DAQmxBaseClearTask (taskHandle);
}
if( DAQmxFailed(error) )
printf("DAQmxBase Error: %s\n",errBuff);
return 0;
}
