I posted a question http://www.xcore.com/questions/3032/audio-clocks in Q&A and user infiniteimprobability suggested that it is more appropriate to post the question here in the forum:
I am designing a prototype board for an audio application using the xmos startkit.
I need one stereo channel output, one mono output and 3 stereo channels input. Sample rate should be fixed, 96kHz or 192kHz. I am using the CS42448 audio codec. I do NOT need any USB audio. Additional there is an external bluetooth chip with SPDIF or I2S output, 48kHz sample rate. The software should then mix all the inputs and the signal from the BT chip in some way and route the audio signal to the outputs. I have finished all the analog parts, the supplies and so on, but now I have troubles to understand requirements for the clocks.
bluetooth chip is the Wt32i from Bluegiga: http://www.mouser.com/ds/2/52/Bluegigga ... 340990.pdf
To read and write all I2S data from the CS42448 at a fixed sample rate of 192kHz (or 96kHz) is it enough to have one crystal oscillator with 24.576MHz and route it like in the attached schematic of the USB Audio 2.0 Ref Design XS1-L1?
To get the bluetooth audio stream on my XMOS startkit is it sufficient to connect the SPDIF_OUT pin from the BT chip to a 1 bit port and decode it with this lib: https://github.com/xcore/sc_spdif or do I need another clock?
For a better understanding of what kind of application I want to realize:
- mix codec stereo input 1 + BT audio (upsampled), create a mono signal, write the mono signal to the codec channel out
- mix codec stereo input 1 + 2 (50% volume) + 3 ( 25% volume) and write mixed signal to codec stereo out
