SigmaStudio sample rate registers
We have the audio codec running but there is a question about the sampling rate that would resolve the issue to our satisfaction. In the Sigma Studio software, there are hardware register settings that set the sampling rate of the chip such as serial port sampling rate, ADC sampling rate and DSP sampling rate. For our application, we set the core clock frequency to 48 KHz and the three sampling rates mentioned to 12 KHz. When testing our system, I set up a square wave source in the schematic window of Sigma Studio to the output and then played it back through our system. There is a field, sample rate window, which can be accessed by right clicking on the square wave source that I set to 12 KHz to match the hardware register settings. When I analyzed the square wave coming over the I2S bus however, the frequency I measured was 750 Hz vs. the 500 Hz the square wave source was set to. The only way to get the frequency I was expecting was to set the sample rate window setting to 18 KHz. This was the case regardless of what frequency I set the square wave source to.
My question then is: why must the sample rate window be set to 18 KHz when the hardware registers are set to 12 KHz and the core clock frequency is 48 KHz?
Hi,
Can you send me a project file and let me know which product you are working with?
Best Rgds,
Alan
Hi Alan,
Attached is my customers project file. The part they are working with
is the ADAU1761.
Let me know if you have any other questions,
Greg Bucik
Field Applications Engineer
Arrow Electronics Canada, Ltd.
Engineering & Design Services
Phone: (905) 565-4405
Cell: (416) 805-8546
Fax: (905) 565-4404
Mobile Email: gbucik@rogers.blackberry.net
Hi Greg,
I noticed the sample rate in your schematic did not match the DSP sample rate setting. Here is an FAQ about how to change the DSP sample rate. Let me know if this fixes the issue
https://ez.analog.com/docs/DOC-1431
Best Rgds,
Alan
Hi Alan,
As per my customer - The discrepancy between the sample rate in the
schematic and the DSP sample rate setting is necessary to output the
same frequency as the source in the schematic. It is this discrepancy
that we are wondering about.
Greg
Hi Greg,
Not sure if we're talking about the same sample rate. There is an fs setting in the toolbar beside the download button as well as for the square wave generator. Anyhow here is a project file that correctly outputs the 500Hz square wave. Are they using a 12.288Mhz clock input? Let me know if this works and answers your question.
Best Rgds,
Alan
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