I am testing the example projects coming with the VDSP5.1, for the project "21489 AD1939 C Block-Based Talkthru 48 or 96 kHz" the input is sine wave of 1kHz.

A breakpoint is set in the function "void handleCodecData(unsigned int blockIndex)" to observe the input data stored in RxBlock_A0 and

RxBlock_A1. However, I am confused with the figure plotted with these data as shown below, the data format is int.

The TDM has four slots for receiver, so I decimate these data by four and replot the figure, but it is also not an entire sine waveform.

Could anyone give me some explanation on this?

Many thanks!

It looks like a full sine wave, but the block processing appears to be garbled on a block basis. From this plot, it looks like it takes 6 blocks to represent one full period of the sine wave. If you consider t=~50.0 as the starting point and call that block 0 (from ~50-80), then the next correct data is (sequentially):

block 5 (t = ~205-240)

block 4 (t = ~175-205)

block 3 (t = ~142-175)

block 2 (t = ~115-142)

block 1 (t = ~80-115)

What does your decimation code do?

-Joe