Abnormal Waveform from myRIO FPGA Audio IN terminal

[charansai]

Hello there!

I am working on Active Noise Cancellation Project on myRIO 1900.

I just figured out the abnormal waveform coming out of Audio IN (FPGA node). 

I am using a 1 V amplitude,2 kHz frequency(0.5msec Time Period), 20k sample rate and 80 #samples sinusoidal noise as source.

I just read this noise using microphone on both RT side and FPGA side seperately. On RT side, I used FPGA High throughput mode(Custom FPGA personality) Audio IN terminal @40k sample rate, and 100 samples. The recorded waveform is  

Where as on the FPGA side, I can only record 1 sample at a time. MyRIO 1900 has 500 kS/sec ADC, and If I am using both left and right channels of Audio In, I am getting loop rate of 4 micro seconds (250 kS/sec for each channel). i.e If I can process, 1 sample in 4 micro seconds, over the Time period of 0.5 msec of sinusoide , Audio IN terminal should be able to collect 125 samples of data for one cycle of sinusoid. So, It should be able to give close to perfect sinusoid even with little loss of data ! But here I am getting some abnormal waveform which  is not at all sinusoid.

I could not understand why is this happening?

Please help me understand what I am doing wrong ! 

Thank You.

[charansai]

Ohh it is working fine if I use DMA FIFO Transfer to RT side and observe it on RT side. Seems like there is some problem with the waveform chart.