DSP Reverb example

[Kevin_M]

LV 8.2.1 & DSP 2.0 & DSK6711

Hi All,

When I run the "Reverb.VI" example, I note the following:  I feed a sinewave in to the DSK and observe the output on a scope. Turn the sliders down to zero, so effectively the VI just reads the input and sends to the output.  The output sine wave is delayed compared to the input sine wave by 53 msec. With DSK6711, sampling frequency is 8 kHz and samples per frame is 128, so it will take 16 msec to fill a frame.  I read in the help about double buffering, so maybe the 53msec delay is made up of 2*16msec +1*16msec + 5 mec = 53 msec. Where is the 5 msec delay coming from?

Similarly, I have a VI which reads an analogue input and sends it to an analogue output with a While loop around it. Nothing else in the VI.  I'm feeding in a sine wave from a signal generator to the line in on my DSK and looking at the output generated by my VI on the line out.  I obseve on my scope that the output sine wave is delayed compared to the input sine wave by 5 msec.  Where is the 5 msec. delay coming from?

Thanks in advance,

Kevin_M

[Tom.]

Hello,

I forwarded this to our R&D team to see if they had any ideas on the delay you were experiencing and they suggested that turning a slider down to zero doesn't aliviate computations that could be causing the delay you're seeing. The 6711 doesn't have a floating point unit, so the floating point arithmetic has to be emulated, which introduces more delay. They suggest wiring an input directly to an ouptut and measure the delay.

Cheers

Tom | NIUK