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Overclock to 153.6 MHz (instead of 147.6 MHz) for I²S 48 kHz sample rate (#2708)

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Markus Gyger 2024-12-21 22:36:57 +07:00 committed by GitHub
parent 4d03edc7d5
commit 7961d2943d
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GPG key ID: B5690EEEBB952194
3 changed files with 4 additions and 6 deletions
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2
docs/i2s.rst
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@ -71,7 +71,7 @@ sample rate on-the-fly.
bool setSysClk(int samplerate)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Changes the PICO system clock to optimise for the desired samplerate.
The clock changes to 147.6 MHz for samplerates that are a multiple of 8 kHz, and 135.6 MHz for multiples of 11.025 kHz.
The clock changes to 153.6 MHz for samplerates that are a multiple of 8 kHz, and 135.6 MHz for multiples of 11.025 kHz.
Note that using ``setSysClk()`` may affect the timing of other sysclk-dependent functions.
Should be called before any I2S functions and any other sysclk dependent initialisations.

6
libraries/I2S/src/I2S.cpp
View file

@ -123,12 +123,10 @@ bool I2S::setFrequency(int newFreq) {
bool I2S::setSysClk(int samplerate) { // optimise sys_clk for desired samplerate
if (samplerate % 11025 == 0) {
set_sys_clock_khz(I2SSYSCLK_44_1, false); // 147.6 unsuccessful - no I2S no USB
return true;
return set_sys_clock_khz(I2SSYSCLK_44_1, false);
}
if (samplerate % 8000 == 0) {
set_sys_clock_khz(I2SSYSCLK_8, false);
return true;
return set_sys_clock_khz(I2SSYSCLK_8, false);
}
return false;
}

2
libraries/I2S/src/I2S.h
View file

@ -163,5 +163,5 @@ private:
int _sm, _smMCLK;
static const int I2SSYSCLK_44_1 = 135600; // 44.1, 88.2 kHz sample rates
static const int I2SSYSCLK_8 = 147600; // 8k, 16, 32, 48, 96, 192 kHz
static const int I2SSYSCLK_8 = 153600; // 8k, 16, 32, 48, 96, 192 kHz
};