Hi, I am trying to generate 100kHz quadrature encoder signal on 2 DO lines on PXI-6229. The DO uses counter0 and PFI0 as an external clock source.
The encoder signal should consist of 10000 periods therefore I use 400kHz sampling rate and send 40000 samples (4 samples each period).
The DAQ throws an error:
Onboard device memory underflow. Because of system and/or bus-bandwidth limitations, the driver could not write data to the device fast enough to keep up with the device output rate.
Reduce your sample rate. If your data transfer method is interrupts, try using DMA or USB Bulk. You can also use a product with more onboard memory or reduce the number of programs your computer is executing concurrently.
I found that using Interrupts instead of DMA as the data transfer mechanism allows me to generate such signal. However I am not sure if this is the correct solution as it depends on CPU load.
I read that DMA is the fastest method to transfer data. Then why can't it keep up with the 400kHz clock?
Thank you.