Processing acquired data (8 simultaneous channels) in RT host (producer,consumer problem)

Question

Hi Gents,
I have a Crio 9024 and two delta sigma modules NI 9234, I have to acquire 8 cahnnels simultaneously at 51,2 kHz from FPGA and transfert this data via DMA fifo to the RT host for proceesing (FFT for all channels and send data to a host computer via a stream network). I succeed to do this with 25,6KHz as sampling frequency but when I tried with 51,2KHz (my goal) I had problem because in RT code I have a producer loop receiveing data from fpga (DMA fifo) and sending this data to a consumer (Queue) loop in RT also for processing this data but the producer is to fast so the consumer loop can't proccess data in time and the queue is overflow. I have replaced queues with RT fifo,single process variable,... but no luck !!!
Any way how to send 8 channels data from one loop to other for processing (base band FFT N channels) at 51,2KHz ???
Please I need help !!!

Answer 1

DMA Fifo:
To avoid overflow you have to configure the RT side which has a default size of 10000 (Rio4.0 and above 2^14 elements) or doubled FPGA depth (fifo_config)
RT Fifo:
config example
Read data from DMA to RT Fifo
(read all elements available and write this data block to your RT fifo, which is configured to hold n-Blocks of size x, i.e. 300Blocks of 18432elements each)
--> here I suggest to read a multiple of 8, because of your channel count
Read data from RT fifo to stream
(send data blocks to the host where each block is one element in terms of streaming buffer --> configure streaming buffer)
Configuring large RT Fifo's has an impact on memory usage, so have an eye on it.
Screens are just examples (not functional code)
Hope it helps
Christian