External Trigger setup

[andma]

Hi,

I would like to have some help in setting the board up for my application. We will be using the internal clock and external trigger for sampling. On every trigger event we would like to sample one sample and then wait for the next trigger.

I have enabled channel 0 and external trigger source and I think I should use Framed trigger mode, is this correct or should I choose Unframed mode?

I don't really know what values to choose for Pkt Size and Frame Size. How will these sizes affect my sampling? As I understand it the frame size is how many samples to take every trig event and Packet size is how many samples to transfer every "transfer" event, is this correct?

[jhenderson]

The configuration you describe is extremely inefficient when using the stock firmware. The stock firmware is designed to capture a frame of data (specified by the frame size) each trigger event. Typically, the frame size is an integer multiple of the packet size, so that each trigger event flows one or more packets to the host for processing.

However, a frame size of one sample results in a packet rate equal to the sample rate. The minimum sample rate for the X3-25M is 4 MHz; A typical Host PC is incapable of reliably processing packet interrupts at this rate.

If you're trying to perform a servo function, typified by per-sample processing, move the algorithm into the FPGA and use Matlab or VHDL to develop the custom firmware.

If your trying to implement a data acquisition function, increase the frame and packet sizes so that interrupts occur at ~100Hz. At 1 MHz, this would equate to a packet size of 10000 samples.