How are these values calculated？

[KinhoLeung]

const I2S_CLK_CONFIG I2S_Clk_Config24[3] = {
{429, 4, 19, 0, 0x0B065E56}, // 44.0995
{384, 5, 12, 1, 0x0C000000}, // 48.0000
{424, 3, 11, 1, 0x1800ED70} // 96.0144
};

How are these values calculated？
0x0B065E56
0x0C000000
0x1800ED70

[har-in-air]

Been a long time,  it took me some time to read the code and see if I could recollect. The feedback value is calculated as a fixed point 10.14 value (10 integer bits, 14 fractional bits) left justified by 8 bits in a uint32.  So 48kHz is represented  by (48.0 x 2^14) << 8 = 201326592 = 0xC000000 For the other values, I'm getting a slight discrepancy in the least significant fractional bits  using the values 44.0995 and 96.0144.   Maybe the actual frequency calculated from the register settings has more significant decimal points.  I don't remember, you can cross check with the reference manual to see how the actual Fs is calculated using these register values and see if the (full precision decimal value multiplied by 2^22) << 8  matches whats in the code. regardsHari On Wednesday 7 May, 2025 at 02:22:02 pm IST, kinho ***@***.***> wrote: KinhoLeung created an issue (har-in-air/STM32F411_USB_AUDIO_DAC#32) const I2S_CLK_CONFIG I2S_Clk_Config24[3] = { {429, 4, 19, 0, 0x0B065E56}, // 44.0995 {384, 5, 12, 1, 0x0C000000}, // 48.0000 {424, 3, 11, 1, 0x1800ED70} // 96.0144 }; How are these values calculated？ 0x0B065E56 0x0C000000 0x1800ED70 — Reply to this email directly, view it on GitHub, or unsubscribe. You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[har-in-air]

That should be (full precision decimal value x 2^14) << 8 regard On Friday 9 May, 2025 at 11:34:48 am IST, Hari Nair ***@***.***> wrote: Been a long time,  it took me some time to read the code and see if I could recollect. The feedback value is calculated as a fixed point 10.14 value (10 integer bits, 14 fractional bits) left justified by 8 bits in a uint32.  So 48kHz is represented  by (48.0 x 2^14) << 8 = 201326592 = 0xC000000 For the other values, I'm getting a slight discrepancy in the least significant fractional bits  using the values 44.0995 and 96.0144.   Maybe the actual frequency calculated from the register settings has more significant decimal points.  I don't remember, you can cross check with the reference manual to see how the actual Fs is calculated using these register values and see if the (full precision decimal value multiplied by 2^22) << 8  matches whats in the code. regardsHari On Wednesday 7 May, 2025 at 02:22:02 pm IST, kinho ***@***.***> wrote: KinhoLeung created an issue (har-in-air/STM32F411_USB_AUDIO_DAC#32) const I2S_CLK_CONFIG I2S_Clk_Config24[3] = { {429, 4, 19, 0, 0x0B065E56}, // 44.0995 {384, 5, 12, 1, 0x0C000000}, // 48.0000 {424, 3, 11, 1, 0x1800ED70} // 96.0144 }; How are these values calculated？ 0x0B065E56 0x0C000000 0x1800ED70 — Reply to this email directly, view it on GitHub, or unsubscribe. You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>