EVAL-ADAU1701MINIZ: SigmaStudio's EQs control wrong frequencies
Hello, I am trying to configure above evaluation board as per screenshot below.
For the EQ, I use “Filters, Second order, Double precision, 2 Ch, Medium Size Eq”. The only thing I have changed is the frequency of each, the remaining parameters being as they come in the program (i.e. Peaking EQ, Q=1.41).
But: After “Link Compile Download”, the frequency bands controlled are not those I have entered, instead they are at approx. 1/4th of the frequencies I have chosen.
E.g. trying to control 1kHz, the real frequency it controls is around 250Hz. The same thing happens with all the other frequencies, e.g. the 16kHz EQ controls around 4kHz.
Am I doing something wrong here?
Thank you for your help.
equalization
adau 1701
Hello Prius,
What is the sample rate set to within the SigmaStudio schematic? This is important in order to generate the proper download parameters for the filters.
What are your settings for the DSP Core Control Register's (address 0x881c) Sample Rate bits D0/D1 ?
Are you perhaps generating coefficients for 192 kHz operation within SigmaStudio, and the ADCs/DACs (or serial ports) are set for 48 kHz? This could explain the frequency shift of the filters being 1/4th of the frequency of operation. When I tell SigmaStudio for 192 kHz operation, and set the program length to 1024 instructions/sample under the HW Configuration tab to set the core for 48 kHz operation, I can hear the frequency of the filters operate at 1/4th the intended frequency. If I switch to 512 instructions/sample, the filter's center frequency is 1/2 what I expect.
The OLF bits in the "Serial Port Control Register 0" (at address 0x081E) for L/R I2S clock operation must also match the instruction sample rate (although you probably are not connecting up to external ADCs or to the eval board so you can ignore this register).
-JT
Thanks very much JohnTo, that was really helpful:
I use 192kHz but the word length was 1024; I have reduced it to 256 and now the EQ frequencies are the correct ones.
Thank you again.
Prius
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