USB-1808x, analog output retriggering and BIDACTRIGCOUNT

[jms]

I have a USB-1808x, and would like to set up an analog output scan that contains N*M samples.  For each input trigger, output N samples, and after M triggers, restart at the beginning.  Is this possible?  I have it working fine with M=1, but the BIDACTRIGCOUNT setting does not seem to have any effect when I try to have a single output scan cross multiple triggers.  Instead, it simply outputs the entire scan on every trigger.

Here is a simplified version of my code showing what I am trying to do:

long rate = 10000;
int numTriggerSamples = 1000;
int numTriggers = 5;
int numTotalOutputSamples = numTriggerSamples * numTriggers;

HGLOBAL winbuf = cbWinBufAlloc(numTotalOutputSamples);
unsigned short *dataArray = (unsigned short*)winbuf;
for (int i=0; i<numTotalOutputSamples; i++) {
  cbFromEngUnits(boardNum, BIP10VOLTS, (float)i / numTotalOutputSamples, &dataArray[i]);
}

ULStat = cbSetTrigger(boardNum, TRIG_POS_EDGE, 0, 0);
if (ULStat != NOERRORS) {
  return;
}

ULStat = cbSetConfig(BOARDINFO, boardNum, 0, BIDACTRIGCOUNT, numTriggerSamples);
if (ULStat != NOERRORS) {
  return;
}

int options = BACKGROUND | EXTTRIGGER | CONTINUOUS | RETRIGMODE;
ULStat = cbAOutScan(boardNum, 0, 0, numTotalOutputSamples, &rate, BIP10VOLTS, winbuf, options);

if (ULStat != NOERRORS) {
  return;
}

cbWinBufFree(winbuf);

 

[JRys]

This configuration item needs to be fixed. I tried it with several values and found that the output in my test program was unaffected. I also need clarification about its function; the cbw.h file and UL Help indicate that the count is not the number of triggers but the number of samples output with each trigger. I will contact Engineering for more information and update this post then. 

 

[JRys]

Answer: The USB-1808X does not support the BIDACTRIGCOUNT configuration item. The answer is at the bottom of the USB-1808X UL Help page under the Configuration section. For Retrigger Count, we created .Net functions for BIDITRIGCOUNT and BIDOTRIGCOUNT, but nothing for BIDACTRIGCOUNT. If it was a valid setting for the USB-1808X we would have created a .Net function for it.

[jms]

Hi JRys, thanks for looking into this.  I understand that BIDACTRIGCOUNT is the number of samples - in my example numTriggerSamples is the number of samples that I want to output with each trigger.

I don't understand what you're seeing that is indicating that BIDACTRIGCOUNT is not supported by the USB-1808.  I am looking at the universal library help, and it specifically says that this is supported:

 

 

[JRys]

What needs to be clarified is the section above, called Retrigger Count, which lists only the BIDITRIGCOUNT and BIDOTRIGCOUNT. You're right; it reads as if it should work. I just sent an email off to engineering for clarity. I will update this post when I have more information.

 

[JRys]

BIDACTRIGCOUNT must be broken or not supported for the USB-1808X.  I switch to USB-1608GX-2AO, and the same code mostly worked. I couldn't use just any trigger count, increments of 1024 and a buffer size of 10,240 worked best. When I got fancy and tried 1536, it got confused and output 3072. However, 1024, 2048, 3072, 4096, 5120, 6144, 8192, and 9216 all worked great.