ADAU1701: change to low sampling frequency for LF signal processing
Hi all,
i'd like to reduce the sampling frequency of the ADAU1701 to have more processing power for low frequency signal processing.
So if i reduce to e.g. 16kHz sampling frequency via 'Set system sampling rate' (see attached picture) and/or 'Propagate sampling rate', the ADC sampling rate should also be reduced. But if i measure the amplitude response (analog in > no processing > analog out), there is no difference in the amplitude response when configured to 48kHz !?
As a test i got a 10kHz analog signal at the input and have this also at the output (sampling = 48kHz). Now i set the sampling rate to 16kHz and the 10kHz signal appears stable at the output (after pressing 'Link Compile Download). How can this be ?
regards
Bernd
Audio Signal Processors
change_sampling_frequency
SigmaDSP Audio Processors
adau1701
Bernd,
That procedure will only change the parameter values used by the software. When changing the sample rate for a system, you need to change the hardware sample rate as well. Please check this FAQ post for more details.
You'll notice that the hardware settings in the ADAU1701 only allow you to select 44.1/48 kHz (normal), 88.2/96 kHz (double), and 176.4/192 kHz (quad) rates. The ADAU1701 cannot process audio at sample rates below 44.1 kHz. That is a limitation of the hardware. Even if it was possible to process at lower rates like 16 kHz, you would not get additional processing power, because the program RAM size is fixed. At 44.1/48 kHz, the full program RAM is already utilized; there is no room in memory for extra program instructions.
Processors like the ADAU1761 can process audio at rates down to 8 kHz, but they have the same program memory limitation. Since the program RAM size is fixed (and optimized for 48 kHz mode), processing at lower rates will not buy you extra processing power - it will only decrease power consumption.
Please log in to reply.