Hi,
I am trying to interface SPH0645LM4H-B mic sensor with STM32L476RG on SAI.
I have configured the SAI2 block A with following configuration.
Master clock :- 2.826 Mhz
Sampling rate :- 44KHZ
//////////////////// PLL configuration /////////////////////
RCC_ExCLKInitStruct.PeriphClockSelection = RCC_PERIPHCLK_SAI2;
RCC_ExCLKInitStruct.Sai2ClockSelection = RCC_SAI2CLKSOURCE_PLLSAI2;
RCC_ExCLKInitStruct.PLLSAI2.PLLSAI2Source = RCC_PLLSOURCE_MSI;
RCC_ExCLKInitStruct.PeriphClockSelection = RCC_PERIPHCLK_SAI2;
//RCC_ExCLKInitStruct.PLLSAI2.PLLSAI2M = 0;
RCC_ExCLKInitStruct.PLLSAI2.PLLSAI2N = 24;
RCC_ExCLKInitStruct.PLLSAI2.PLLSAI2P = 17;
RCC_ExCLKInitStruct.PLLSAI2.PLLSAI2ClockOut = RCC_PLLSAI2_SAI2CLK;
RCC_ExCLKInitStruct.Sai2ClockSelection = RCC_SAI2CLKSOURCE_PLLSAI2;
//////////////////////////////////////////////////////////////////////
////////////////// SAI CONFIGURATION ////////////////////////
BSP_AUDIO_hSai.Instance = AUDIO_SAIx; /*this is SAI2 block A*/
BSP_AUDIO_hSai.hdmarx = &hDmaSai;
/* Configure SAI_Block_x
LSBFirst: Disabled
DataSize: 24 */
BSP_AUDIO_hSai.Init.AudioMode = SAI_MODEMASTER_RX;
BSP_AUDIO_hSai.Init.Synchro = SAI_ASYNCHRONOUS;
BSP_AUDIO_hSai.Init.SynchroExt = SAI_SYNCEXT_DISABLE;
BSP_AUDIO_hSai.Init.OutputDrive = SAI_OUTPUTDRIVE_DISABLE;
BSP_AUDIO_hSai.Init.NoDivider = SAI_MASTERDIVIDER_ENABLE;
BSP_AUDIO_hSai.Init.FIFOThreshold = SAI_FIFOTHRESHOLD_HF;
BSP_AUDIO_hSai.Init.AudioFrequency = AudioFreq;
BSP_AUDIO_hSai.Init.Mckdiv = SAIClockDivider(AudioFreq);
//BSP_AUDIO_hSai.Init.MonoStereoMode = SAI_MONOMODE;
BSP_AUDIO_hSai.Init.MonoStereoMode = SAI_MONOMODE;
BSP_AUDIO_hSai.Init.CompandingMode = SAI_NOCOMPANDING;
BSP_AUDIO_hSai.Init.TriState = SAI_OUTPUT_NOTRELEASED;
if (HAL_SAI_InitProtocol(&BSP_AUDIO_hSai, SAI_I2S_STANDARD, SAI_PROTOCOL_DATASIZE_24BIT, 2) != HAL_OK)
{
return AUDIO_ERROR;
}
/* Enable SAI peripheral to generate MCLK */
__HAL_SAI_ENABLE(&BSP_AUDIO_hSai);
////////////////////////////////////////////////////////////////////////////////////////
I am reading data directly from the sai data register after reading status register.
if ((sai->SR)&0x1) {
sai->CLRFR |= 1; // Clear Overdue
}
Timer t;
int start = millis();
while (i < len) {
if (millis() - start > timeout) return -1;
int printed = 0;
while ((((sai->SR)>>16) & 7) < 4) {
if (!printed) {
while(j < i) {
pc.printf("%d\n", buf[j++]);
}
printed = 1;
}
i = j = 0;
}
uint32_t data = sai->DR;
buf[i++] = (data << 😎 >> 14;
}
The issue i am getting here is that the data i am getting has variation in only 8 bits like the following:
data is in hexadecimal
255360
255365
255364
255355
255350
255349
255342
255347
255346
255344
255341
255346
255356
255348
255348
255346
255343
255340
255361
255355
I have checked the clocks with CRO and i am getting 44khz clock at data pin and 2.8Mhz clock at master clock but unable to get any clock at WS pin.
Not sure if i am doing something wrong over here.
Although when i try to plot the data received on Arduino serial plotter, there is change in waveform when i blow into the mic but when i tried to create a file from the data and play it (on audacity) i get nothing but noises.
A little help would be appreciable, I am blocked at this.
Thanks
