Hello,
I am using a MEMS PDM microphone and reading it in using I2S. The following parameters are set in my I2S and PDM configurations.
hi2s3.Instance = SPI3;
hi2s3.Init.Mode = I2S_MODE_MASTER_RX;
hi2s3.Init.Standard = I2S_STANDARD_MSB;
hi2s3.Init.DataFormat = I2S_DATAFORMAT_24B;
hi2s3.Init.MCLKOutput = I2S_MCLKOUTPUT_DISABLE;
hi2s3.Init.AudioFreq = I2S_AUDIOFREQ_48K;
hi2s3.Init.CPOL = I2S_CPOL_LOW;
hi2s3.Init.ClockSource = I2S_CLOCK_PLL;
hi2s3.Init.FullDuplexMode = I2S_FULLDUPLEXMODE_ENABLE;
The PDM2PCM decimation factor is 64. I am sending the data out of the uart at 2Mbaud, but am getting gaps of corrupt values in my data. Is this because I am not sending it fast enough? If so, how could I buffer this better in order to fix this issue?
Thanks for any help, my code is here as well and an image of my plotted audio.
HAL_I2S_Receive_DMA(&hi2s3, &pdmRxBuf[0],64);
HAL_UART_Transmit_DMA(&huart2, (uint8_t *)txBuf, 256);
/* USER CODE END 2 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
if (rxstate==1) {
PDM_Filter(&pdmRxBuf[0],&MidBuffer[0], &PDM1_filter_handler);
for (int i=0; i<16;i++)
{
//MidBuffer[i] = j++;
FifoWrite(MidBuffer[i]);
//j %= 65535;
}
if (fifo_w_ptr-fifo_r_ptr > 128) fifo_read_enabled=1;
rxstate=0;
}
if (rxstate==2) {
PDM_Filter(&pdmRxBuf[64],&MidBuffer[0], &PDM1_filter_handler);
for (int i=0; i<16;i++)
{
//MidBuffer[i] = j++;
FifoWrite(MidBuffer[i]);
//j %= 65535;
}
rxstate=0;
}
if (txstate==1) {
if (fifo_read_enabled==1) {
for (int i=0; i<64;i=i+1) {
uint16_t data = FifoRead();
txBuf[i] = data;
//txBuf[i+2] = data;
}
}
txstate=0;
}
if (txstate==2) {
if (fifo_read_enabled==1) {
for (int i=64; i<128;i=i+1) {
uint16_t data = FifoRead();
txBuf[i] = data;
// txBuf[i+2] = data;
}
}
txstate=0;
}
void HAL_UART_TxHalfCpltCallback(UART_HandleTypeDef *huart)
{
txstate = 1;
}
void HAL_UART_TxCpltCallback(UART_HandleTypeDef *huart)
{
txstate = 2;
}
void HAL_I2S_RxHalfCpltCallback (I2S_HandleTypeDef *hi2s) {
rxstate = 1;
}
void HAL_I2S_RxCpltCallback (I2S_HandleTypeDef *hi2s) {
rxstate = 2;
}
