ADAU1452 sampling frequency
I'm working on ADAU1452miniZ board.
I took new project, and keep all default values. I just enabled SPDIF (through ASRC0) and SPDIF Out.
Master clock from oscillator is 12.288Mhz. PLL is set to /4 and then *96=> DSP system clock is 294.912MHz
I made following very simple schematics: just a FIR filter. I designed it to be bandpass (200Hz to 4kHz) @48kHz.
Input is SPDIF @48kHz.
If I set DSP sampling frequency at 48kHz=> OK I get expected frequency response (measured with Audio precision).
but if I increase DSP sampling frequency to 96k, measured frequency response of filter is unchanged (I expected it to be shifted by an octave).
I noticed that simulated value in Sigmastudio (using probe and stimulus) is correctly shifted.
I also noticed that sampling frequency on SPDIF output is always 48kHz, whatever selected DSP sampling frequency.
Shouldn't be same as DSP fs?
Can you help me to understand why DSP sampling frequency setting has no effect?
Thank you
Audio Signal Processors
adau1452
SigmaDSP Audio Processors
Hello DaveThib,
Would you have any comments about this question on how to use down/up sampling?
Thank you
Davker
Hello Davker,
So where are you changing the sampling frequency? If it is only in sampling rate box on the top of the window in SigmaStudio then you are not actually changing the sampling frequency. This number in SigmaStudio changes the settings of the software where it needs to know what the fs is for timing reasons. Otherwise, the sampling rate is set by hardware and register settings.
You have to change the start pulse in the Core control tab. This changes the sampling rate of the core. Then you probably have to change the serial port sampling rates as well but... The MiniZ cannot change to a different sample rate if you are using the Codec. Using the SPDIF output you are fine and you are also using the SPDIF input so you will not have to worry about the serial port rates. You also have to set the ASRC output rate to match the core rate. Either use the same clock source or just set it to the Start pulse rate. Then it will follow the start pulse register setting.
Give that a try and I think it will work better. I don't think I am missing something...
Dave T
Hello Dave,
Yes, I thought that sampling rate box on the top of window in sigmastudio was automatically adjusting register in DSP (start_pulse). I did as you said, and now it is working OK (using SPDIF in and out).
Thank you
davker.
Hello Dave,
I have made DSP project which is running at 192kHz.
I have two questions:
-Because Codec can't work at this sampling freq on miniz board, I have routed DSP outputs to DAC through ASRC (downsampled to 48kHz).
This is working properly, but, I measure several dB attenuation after 10kHz if internal fs is 192kHz compared to 48kHz.
How can I attach projet ?
-On SPDIF output, I have distortion in high frequencies (example 15kHz) when I used 192kHz (I don't have it at 48kHz). What is it due to?
Thank you
Davker
Hello davker,
The SPDIF ports on this part are only specified to 96kHz fs max. We do have a new drop-in replacement part that can operate the SPDIF up to 192kHz, it is due to release in June or early July.
I am not certain where the roll-off is coming from. You can attach the project by using the "advanced editor". It is a clickable link up in the upper right of the reply window. It would be handy to see your project.
Dave T
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