G'day!
I've been reading up on how to use the I2S module in my K70 elevator tower with the SGTL as the TWR-AUDIO extension.
I am a little confused as to what the right question to as is..
So I have the system oscillator set at 50Mhz as default and have noticed the I2S module is derived from the (Core/System clock)*((I2SFrac+1/I2SDiv+1)). For example, If I wanted 48 Khz as my sampling rate, I would multiply by 256 to get 12.288 Mhz for the I2S clock.
And further more, on the next page,
I could not find the I2Sx_PCCR register in the K70 Sub-Family Reference Manual, so I don't know what PM stands for.
My question is "should I be changing the K70 OSC0 to 12.288Mhz or 4Mhz"?
Which I think would be a bad idea due to other clocks prescalar on it...
Another idea I had was that I just keep it at 50Mhz and derive the 12.288Mhz on the Bus Clock but the closest I can get it is 12.5 Mhz which is not good enough.
Thank you for your time!
Hi, Pang,
When the I2S is configured as master, the bit clock and frame clock sources are internal or external. This is the I2S clock source diagram for K70, I copy it from reference manual of K70.
Assume that the sampling clock is 48KHz, you use 32 bits data for left/right channel, the required bit clock frequecy BCLK is 64*48K=3.072MHz. No matter how you divide the clock source and where the clock source is, it is okay if the bit clock frequency is 3.072MHz.
There is not I2Sx_RCCR register for K70, probably you refer to wrong processor by mistake.
Assume that the core/system clock is 50MHz for your case, the Bit Clock Divider is 4, the MCLK must be 3.072M*4=12.288MHz, the MCLK frequency is 12.288MHz. 50MHz/12.288MHz=4.069, I suppose that you can set the FRACT=0, DIVIDE=3, it is okay. The actual bit clock will be 50MHz*1/(4*4)=3.125MHz.
as an alternative, assume that the core/system clock is 50MHz for your case, the Bit Clock Divider is 1, the MCLK must be 3.072MHz. The 50MHz/3.072MHz=16.276, I suppose that you can set the FRACT=99, DIVIDE=1626, it is okay, the actual MCLK will be 50MHz*(99+1)/(1626+1)=3.073MHz, it is okay.
This is the register setting, which I copy from RM of K70:
Hope it can help you
BR
Xiangjun Rong
