The audio signal with 24dB gain set is reasonable quality but seems low in the noise. I added a slew filter which helps a lot, but I expected a clearer audio above the noise.
The clock going to the mic chip is 1,024 MHz, these are my settings, if anyone has any ideas what might be causing this. Clock and data signals look good, little ringing.
/* SETUP USER CODE END I2S3_Init 1 */
hi2s3.Instance = SPI3;
hi2s3.Init.Mode = I2S_MODE_MASTER_RX;
hi2s3.Init.Standard = I2S_STANDARD_PHILIPS;
hi2s3.Init.DataFormat = I2S_DATAFORMAT_16B;
hi2s3.Init.MCLKOutput = I2S_MCLKOUTPUT_DISABLE;
hi2s3.Init.AudioFreq = I2S_AUDIOFREQ_32K;
hi2s3.Init.CPOL = I2S_CPOL_LOW;
hi2s3.Init.FirstBit = I2S_FIRSTBIT_MSB;
hi2s3.Init.WSInversion = I2S_WS_INVERSION_DISABLE;
hi2s3.Init.Data24BitAlignment = I2S_DATA_24BIT_ALIGNMENT_RIGHT;
hi2s3.Init.MasterKeepIOState = I2S_MASTER_KEEP_IO_STATE_DISABLE;
if (HAL_I2S_Init(&hi2s3) != HAL_OK)
END...
void MX_PDM2PCM_Init(void)
{
/* USER CODE BEGIN 2 */
/* USER CODE END 2 */
/**
*/
__HAL_RCC_CRC_CLK_ENABLE();
CRC->CR = CRC_CR_RESET;
volatile static bool bDo = 1;
if (bDo) // RT tester
{
PDM1_filter_handler.bit_order = PDM_FILTER_BIT_ORDER_MSB;
PDM1_filter_handler.endianness = PDM_FILTER_ENDIANNESS_BE; // PDM_FILTER_ENDIANNESS_LE
}
else
{
PDM1_filter_handler.bit_order = PDM_FILTER_BIT_ORDER_LSB;
PDM1_filter_handler.endianness = PDM_FILTER_ENDIANNESS_LE; // PDM_FILTER_ENDIANNESS_BE
}
PDM1_filter_handler.high_pass_tap = 1825361095; //1932735282; // 2104533974; // 2122358088 / 2122358088
PDM1_filter_handler.in_ptr_channels = 1;
PDM1_filter_handler.out_ptr_channels = 1;
uint32_t res = PDM_Filter_Init(&PDM1_filter_handler);
assert(res == 0);
PDM1_filter_config.decimation_factor = PDM_FILTER_DEC_FACTOR_128;
PDM1_filter_config.output_samples_number = 4;
PDM1_filter_config.mic_gain = 24;
res = PDM_Filter_setConfig(&PDM1_filter_handler, &PDM1_filter_config);
assert(res == 0);
/* USER CODE BEGIN 3 */
CIRCULAR DMA IS TRANSFERING 32 HALF-WORDS TO MEMORY:-
void HAL_I2S_RxCpltCallback(I2S_HandleTypeDef *hi2s)
{
#ifdef _DEBUG
#include "main.h"
//HAL_GPIO_WritePin(DEBUG_SIGNAL_GPIO_Port, DEBUG_SIGNAL1_Pin, GPIO_PIN_RESET);
HAL_GPIO_TogglePin(DEBUG_SIGNAL1_GPIO_Port, DEBUG_SIGNAL1_Pin); // Toggle for scope
#endif
static uint8_t uIX = 0;
volatile static bool bClear = 0;
if (!bClear && PDM_Filter(pdmRxBuf, pcmBuffer, &PDM1_filter_handler) == 0) // Get 8KHz mic sample
{
pcmBuffer IS 4 HALF WORDS, DATA ARRIVES.
