Hyperception (RIDE, VAB)

[Kevin_M]

LV 7.1.1 Embedded & DSP 1.0 & DSK6711

Hi All,

I am using LabVIEW DSP (without ever learning LabVIEW) so this may be a simple one:

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..

With 6711 DSK, I can either set my AI / AO to multiple samples or single samples.  Sampling rate on DSK6711 is fixed at 8 kHz.

1) With AI/AO set to single sample, 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?

2) With AI/AO set to multiple samples, I obseve on my scope that 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?

Thanks in advance,

Kevin_M

[SAZ2]

The A/D and D/A routines do make use of double-buffering during the acquisition/generation process and does contribute to the delay you are seeing. Foreground processing associated with moving data into position could be the cause of the additional delay.

[Kevin_M]

Hi Saz2,

Actually I sorted this out - I should have replied to my own query for the benefit of others.

Most of the delay is caused by the sigma/delta A/D and D/A conversion in the Codec.  I compared a code composer file against Labview, and the delay is only marginally worse with Labview, about 32*sample time with code composer and 40*sample time with Labview for TLC320AD535 codec.

Regards,

Kevin