software trigger

[ypasco]

Hi !

I need to find a solution for a specific problem using a software trigger.

I am using a cDAQ system with NI9234 analog input modules and NI9263 analog outup modules.

my application needs to sample at full speed (51.2kHz)

I need to do the acquisition of 10 to 16 channels of microphones and use the first channel as trigger to output a 5V impulse.

The main difficulty is that i need a pre-trigger of about 10 second on my recording and need to output an impulse as soon as my first channel has reached the trigger level.

my recording must be 20s long so that the trigger on the fisrt chanel is at the middle of my recording.

I did try to acquire one sample at a time and stock it in a buffer but it does not work at full speed.

any ideas ?

thanks

[crossrulz]

The trigger level impulse should be done in the FPGA.  That will make things very simple for that.  Use a DMA channel to pass your data up to the RT system.  In the RT, you could read the DMA channel and store the data in a lossy queue.  When the threshold is found, you just get the next 10 seconds worth of data and record everything.  You could probably save the data to disk while recording the additional 20seconds.  This will use a lot of memory.

[ypasco]

Hi !

I don't have a RT platform, just a USB cDAQ... so i can not implement your solution.

thank you

Yann