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Update I2S base frequency and frequency dividers to real ones (#4031)

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* Fix I2S base frequency
* Update frequency dividers for I2S
Reference: https://github.com/espressif/ESP8266_MP3_DECODER/blob/master/mp3/driver/i2s_freertos.c
* fixed i2s_set_rate, added i2s_get_real_rate() and i2s_set_dividers
* Minimise float calculations
This commit is contained in:
Kristijan Gjoshev 2018-01-21 00:58:42 +01:00 committed by Earle F. Philhower, III
parent 38fe6fc488
commit 0fe725909e
3 changed files with 35 additions and 5 deletions
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34
cores/esp8266/core_esp8266_i2s.c
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@ -212,15 +212,43 @@ static uint32_t _i2s_sample_rate;
void ICACHE_FLASH_ATTR i2s_set_rate(uint32_t rate){ //Rate in HZ
if(rate == _i2s_sample_rate) return;
_i2s_sample_rate = rate;
uint32_t i2s_clock_div = (I2SBASEFREQ/(_i2s_sample_rate*32)) & I2SCDM;
uint8_t i2s_bck_div = (I2SBASEFREQ/(_i2s_sample_rate*i2s_clock_div*2)) & I2SBDM;
uint32_t scaled_base_freq = I2SBASEFREQ/32;
float delta_best = scaled_base_freq;
uint8_t sbd_div_best=1;
uint8_t scd_div_best=1;
for (uint8_t i=1; i<64; i++){
for (uint8_t j=i; j<64; j++){
float new_delta = fabs(((float)scaled_base_freq/i/j) - rate);
if (new_delta < delta_best){
delta_best = new_delta;
sbd_div_best = i;
scd_div_best = j;
}
}
}
//os_printf("Rate %u Div %u Bck %u Frq %u\n", _i2s_sample_rate, i2s_clock_div, i2s_bck_div, I2SBASEFREQ/(i2s_clock_div*i2s_bck_div*2));
//!trans master, !bits mod, rece slave mod, rece msb shift, right first, msb right
I2SC &= ~(I2STSM | (I2SBMM << I2SBM) | (I2SBDM << I2SBD) | (I2SCDM << I2SCD));
I2SC |= I2SRF | I2SMR | I2SRSM | I2SRMS | ((i2s_bck_div-1) << I2SBD) | ((i2s_clock_div-1) << I2SCD);
I2SC |= I2SRF | I2SMR | I2SRSM | I2SRMS | ((sbd_div_best) << I2SBD) | ((scd_div_best) << I2SCD);
}
void ICACHE_FLASH_ATTR i2s_set_dividers(uint8_t div1, uint8_t div2){
div1 &= I2SBDM;
div2 &= I2SCDM;
I2SC &= ~(I2STSM | (I2SBMM << I2SBM) | (I2SBDM << I2SBD) | (I2SCDM << I2SCD));
I2SC |= I2SRF | I2SMR | I2SRSM | I2SRMS | (div1 << I2SBD) | (div2 << I2SCD);
}
float ICACHE_FLASH_ATTR i2s_get_real_rate(){
return (float)I2SBASEFREQ/32/((I2SC>>I2SBD) & I2SBDM)/((I2SC >> I2SCD) & I2SCDM);
}
void ICACHE_FLASH_ATTR i2s_begin(){
_i2s_sample_rate = 0;
i2s_slc_begin();

2
cores/esp8266/esp8266_peri.h
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@ -754,7 +754,7 @@ extern uint8_t esp8266_gpioToFn[16];
#define i2c_bbpll_en_audio_clock_out_msb 7
#define i2c_bbpll_en_audio_clock_out_lsb 7
#define I2S_CLK_ENABLE() i2c_writeReg_Mask_def(i2c_bbpll, i2c_bbpll_en_audio_clock_out, 1)
#define I2SBASEFREQ (12000000L)
#define I2SBASEFREQ (160000000L)
#define I2STXF ESP8266_REG(0xe00) //I2STXFIFO (32bit)
#define I2SRXF ESP8266_REG(0xe04) //I2SRXFIFO (32bit)

2
cores/esp8266/i2s.h
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@ -43,6 +43,8 @@ extern "C" {
void i2s_begin();
void i2s_end();
void i2s_set_rate(uint32_t rate);//Sample Rate in Hz (ex 44100, 48000)
void i2s_set_dividers(uint8_t div1, uint8_t div2);//Direct control over output rate
float i2s_get_real_rate();//The actual Sample Rate on output
bool i2s_write_sample(uint32_t sample);//32bit sample with channels being upper and lower 16 bits (blocking when DMA is full)
bool i2s_write_sample_nb(uint32_t sample);//same as above but does not block when DMA is full and returns false instead
bool i2s_write_lr(int16_t left, int16_t right);//combines both channels and calls i2s_write_sample with the result