Some discussion about using the wm8731 with 12.288MHz clock here:
- Rafael
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On 2/29/24 04:00, Dean Souleles wrote:
One mystery solved.? Reporting here for future homebrewers....
With help from Farhan, I diagnosed some of the frequency and audio problems with my homebrew SBITX.? The symptoms are audio stuttering and frequency shifts in the audio.? I'm using Mikroe WM8731 Proto board <>?for the codec.? Here is the source of the problem.? The codec? board has a 12.288MHz crystal on board which is meant for imedding in standard digital sound systems.? The Linux driver the SBITX uses is for a sound card called the audio-injector - which instead uses the USB clock standard of 12MHz.? The WM8731 can use either a 12.288MHz clock in its "Normal mode" or a 12MHz crystal in its "USB mode" which is meant for embedding in USB sound systems.? The driver is apparently programmed only for the USB mode.? All of this has to do with the audio sampling rates and having a mismatch between the board and software causes a variety of problems.
In conclusion, to use the Mikroe proto board I will need to swap he 12.288MHz crystal for a 12MHz crystal.? The 12MHz crystals are ordered and I'll make the swap and report results later.
73,
Dean
KK4DAS
