Here are the results. In short : it does not work. But may be I have made a mistake ?
Here is the code I am running (on a Macbook Pro, with Suse 11.2):
// Channel parameters
char chan[] = "Dev1/ai0, Dev1/ai1, Dev1/ai2, Dev1/ai3";
float64 min = -5.0;
float64 max = 5.0;
// Timing parameters
char clockSource[] = "OnboardClock";
uInt64 samplesPerChan = 0;// = The number of samples to acquire for each channel in the task if sampleMode is DAQmx_Val_FiniteSamps
float64 sampleRate = 51200.0;
// Data read parameters
#define bufferSize (uInt32)512
float64 data[bufferSize * 4];
int32 pointsToRead = bufferSize;
int32 pointsRead;
float64 timeout = 10.0;
int32 totalRead = 0;
printf("Press Ctrl-C to exit\n");
DAQmxErrChk (DAQmxBaseResetDevice("Dev1"));
DAQmxErrChk (DAQmxBaseCreateTask("",&taskHandle));
DAQmxErrChk (DAQmxBaseCreateAIVoltageChan(taskHandle,chan,"",DAQmx_Val_Cfg_Default,min,max,DAQmx_Val_Volts,NULL));
DAQmxErrChk (DAQmxBaseCfgSampClkTiming(taskHandle,clockSource,sampleRate,DAQmx_Val_Rising,DAQmx_Val_ContSamps,samplesPerChan));
DAQmxErrChk (DAQmxBaseCfgInputBuffer(taskHandle,2000000)); //use a 100,000 sample DMA buffer
DAQmxErrChk (DAQmxBaseStartTask(taskHandle));
// The loop will quit after 10 seconds
startTime = time(NULL);
while( time(NULL)<startTime+30 ) {
DAQmxErrChk (DAQmxBaseReadAnalogF64(taskHandle,pointsToRead,timeout,DAQmx_Val_GroupByScanNumber,data,bufferSize*4,&pointsRead,NULL));
totalRead += pointsRead;
compteur++;
printf("(%i) : Acquired %ld samples. Total %ld\n",compteur,pointsRead,totalRead);
}
printf("\nAcquired %ld total samples.\n",totalRead);
It is basically the C example you provided in contAcquireNChan.c
I have tried different values for the buffersize variable (corresponding to the numSampsPerChan parameter), including 512, 256 (corresponding to 8KiB and 4KiB read size), and smaller ones, with no success. Indeed, I get after a few acquisitions :
/usr/local/natinst/nidaqmxbase/examples/ai> ./contAcquireNChan
Press Ctrl-C to exit
(1) : Acquired 2048 samples. Total 2048
(2) : Acquired 2048 samples. Total 4096
(3) : Acquired 2048 samples. Total 6144
(4) : Acquired 2048 samples. Total 8192
(5) : Acquired 2048 samples. Total 10240
DAQmxBase Error -200361: <err>Onboard device memory overflow. Because of system and/or bus-bandwidth limitations, the driver could not read data from the device fast enough to keep up with the device throughput.
Reduce the sample rate, or reduce the number of programs your computer is executing concurrently.
As you can see, I can only read about 10240 samples, and sometimes I get the error message at the very first reading operation.
