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Determine SPDIF input rate with ASRC ratio

Question asked by philipj451 on Jan 29, 2018
Latest reply on Feb 1, 2018 by philipj451


I'm having a bit of confusion in a design using an ADAU1452.

I have a 44.1k signal coming into the spdif input which is set to drive ASRC0. ASRC0 drives my core program (not important what that is). I want to report to the user/operator the incoming sample rate so I read register ASRC0_RATIO (0xf582) and calculate it from what I know the core SampleRate to be.

If the core is running at 48k I get the number 3763 which given that 4096 = 1.0 this says that the core is 48k and the spdif is 44.1k good!

If I change the incoming SPDIF rate the ratio changes appropriatly so also good!!


BUT: If I run the core at 96k I get the same numbers?


I know the core is running at 96k because I am also running the spdif output at core speed and it changes between 48k and 96k when I change the core speed.


How should the settings be in SigmaStudio? In the Routing Matrix tab there are 3 drop down menus for each of the 8 ASRC's I have set them as shown in the bitmap attached but I'm unsure about the top one. Is it ignored because I'm using SPDIF input or does it still have some significance?


Any thoughts or help would be appreaciated