I've got two USB-6210 devices that I need to sync up so that they
both gather data at exactly the same time. I'd like to trigger the data
gathering for each device by sending a trigger out of Dev1/PFI6 and
having both devices receive the trigger on PFI0.
The analog trigger input doesn't seem to work, but the digital trigger input seems to be accepted. Unfortunately, I can't seem to get the clock signal to be exported.
Here is the sample program I'm using:
/*********************************************************************
*
* ANSI C Example program:
* contAcquire-ExtClk-DigStart.c
*
* Example Category:
* AI
*
* Description:
* This example demonstrates how to acquire a continuous amount of
* data using an external sample clock, started by a digital edge.
*
* 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 voltage ranges.
* Note: For better accuracy try to match the Input Ranges to the
* expected voltage level of the measured signal.
* 3. Select a source for the sample clock.
* 4. Set the approximate Rate of the external clock. This allows
* the internal characteristics of the acquisition to be as
* efficient as possible. Also set the Samples to Read.
* 5. Select a source for the digital edge start trigger.
* 6. Select the edge, rising or falling, on which to trigger.
*
* Steps:
* 1. Create a task.
* 2. Create an analog input voltage channel.
* 3. Define the parameters for an External Clock Source.
* Additionally, define the sample mode to be continuous. The
* external clock rate is given to allow the internal
* characteristics of the acquisition to be as efficient as
* possible.
* 4. Set the parameters for a digital edge start trigger.
* 5. Call the Start function to start the acquisition.
* 6. Read the waveform data in a loop until 10 seconds or an
* error occurs.
* 7. Call the Clear Task function to clear the Task.
* 8. Display an error if any.
*
* I/O Connections Overview:
* Make sure your signal input terminal matches the Physical
* Channel I/O control. Also, make sure that your digital trigger
* signal is connected to the terminal specified in Trigger Source.
*
* Recommended Use:
* 1. Call Configure and Start functions.
* 2. Call Read function in a loop.
* 3. Call Stop function at the end.
*
*********************************************************************/
#include "NIDAQmxBase.h"
#include <stdio.h>
#include <time.h>
#include <unistd.h>
#define DAQmxErrChk(functionCall) { if( DAQmxFailed(error=(functionCall)) ) { goto Error; } }
int main(void)
{
// Task parameters
int32 error = 0;
TaskHandle AITaskHandle = 0;
char errBuff[2048]={'\0'};
int32 i;
time_t startTime;
// Channel parameters
char chan[] = "Dev1/ai0";
float64 min = -10.0;
float64 max = 10.0;
// Timing parameters
char clockIn[] = "/Dev1/PFI0";
char clockOut[] = "/Dev1/PFI4";
uInt64 samplesPerChan = 1000;
float64 sampleRate = 10000.0;
// Triggering parameters
char triggerIn[] = "/Dev1/PFI2";
char triggerOut[] = "/Dev1/PFI6";
uInt32 triggerSlope = DAQmx_Val_RisingSlope;
uInt32 triggerSamples = 100;
// Data read parameters
#define bufferSize (uInt32)1000
float64 data[bufferSize];
int32 pointsToRead = bufferSize;
int32 pointsRead;
float64 timeout = 10.0;
int32 totalRead = 0;
printf("calling CreateTask - AI...\n");
DAQmxErrChk (DAQmxBaseCreateTask("",&AITaskHandle));
printf("calling CreateAIVoltage - AI...\n");
DAQmxErrChk (DAQmxBaseCreateAIVoltageChan(AITaskHandle,chan,"",DAQmx_Val_Cfg_Default,min,max,DAQmx_Val_Volts,NULL));
//printf("calling CfgSampleClkTiming - AI...\n");
// DAQmxErrChk (DAQmxBaseCfgSampClkTiming(AITaskHandle,clockIn,sampleRate,DAQmx_Val_Rising,DAQmx_Val_ContSamps,1000));
printf("calling CfgSampleClkTiming - AI...\n");
DAQmxErrChk (DAQmxBaseCfgSampClkTiming(AITaskHandle,"OnboardClock",sampleRate,DAQmx_Val_Rising,DAQmx_Val_ContSamps,1000));
printf("calling DigEdgeStartTrig...\n");
DAQmxErrChk (DAQmxBaseCfgDigEdgeStartTrig(AITaskHandle,triggerIn,triggerSlope));
printf("calling ExportSignal - sample clock on %s...\n", clockOut);
DAQmxErrChk (DAQmxBaseExportSignal(AITaskHandle, DAQmx_Val_SampleClock, clockOut));
printf("calling StartTask - AI\n");
DAQmxErrChk (DAQmxBaseStartTask(AITaskHandle));
// The loop will quit after 10 seconds
startTime = time(NULL);
while( time(NULL)<startTime+10 ) {
printf("loop - calling ExportSignal - Trigger...\n");
DAQmxErrChk (DAQmxBaseExportSignal(AITaskHandle, DAQmx_Val_StartTrigger, triggerOut));
printf("loop - calling ReadAnalogF64...\n");
DAQmxErrChk (DAQmxBaseReadAnalogF64(AITaskHandle,pointsToRead,timeout,DAQmx_Val_GroupByChannel,data,bufferSize,&pointsRead,NULL));
totalRead += pointsRead;
printf("Acquired %d samples. Total %d\n",pointsRead,totalRead);
// Just print out the first 10 points of the last data read
for (i = 0; i < 10; ++i)
printf ("data[%d] = %f\n", i, data[i]);
}
printf("\nAcquired %d total samples.\n",totalRead);
Error:
if( DAQmxFailed(error) )
DAQmxBaseGetExtendedErrorInfo(errBuff,2048);
if(AITaskHandle != 0) {
DAQmxBaseStopTask (AITaskHandle);
DAQmxBaseClearTask (AITaskHandle);
}
if( DAQmxFailed(error) )
printf ("DAQmxBase Error %d: %s\n", error, errBuff);
return 0;
}
And here is the result of running the sample program.
$ ./contAcquire-ExtClk-DigStart
calling CreateTask - AI...
calling CreateAIVoltage - AI...
calling CfgSampleClkTiming - AI...
calling DigEdgeStartTrig...
calling ExportSignal - sample clock on /Dev1/PFI4...
DAQmxBase Error -200428: Value passed to the Task/Channels In control is invalid.
Can anyone tell me what I'm doing wrong or is ExportSignal not supported for USB-6210 devices on Linux?
Thanks,
-Tom
