Solved
Unable to convert PDM data to PCM data using pdm2pcm
I'm using a stm32wb55RG. I'm trying to get data from a MEMS PDM microphone and convert it into PCM data. I'm using SAI PDM interface and DMA. So far, I think I manage to receive the PDM data (I get some values from the SAI interface) :
I don't know if these values make a sense or not. But when I try to convert these data into PCM using PDM_Filter, I can't get any value in the output buffer.
I provide the code :
#include "main.h"
#include "pdm2pcm_glo.h"
#include "stdio.h"
/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
/* USER CODE END Includes */
/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */
/* USER CODE END PTD */
/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
/* USER CODE END PD */
/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */
/* USER CODE END PM */
/* Private variables ---------------------------------------------------------*/
SAI_HandleTypeDef hsai_BlockA1;
DMA_HandleTypeDef hdma_sai1_a;
UART_HandleTypeDef huart1;
PCD_HandleTypeDef hpcd_USB_FS;
/* USER CODE BEGIN PV */
/* USER CODE END PV */
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
void PeriphCommonClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_USART1_UART_Init(void);
static void MX_DMA_Init(void);
static void MX_USB_PCD_Init(void);
static void MX_SAI1_Init(void);
/* USER CODE BEGIN PFP */
/* USER CODE END PFP */
/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
uint8_t rxstate = 0;
uint8_t PDM_Buffer[1024];
/* PDM-PCM conversion configuration */
PDM_Filter_Handler_t PDM_FilterHandler;
PDM_Filter_Config_t PDM_FilterConfig;
/* USER CODE END 0 */
/**
* @brief The application entry point.
* @retval int
*/
int main(void)
{
/* MCU Configuration--------------------------------------------------------*/
/* Reset of all peripherals, Initializes the Flash interface and the Systick. */
HAL_Init();
/* Configure the system clock */
SystemClock_Config();
/* Configure the peripherals common clocks */
PeriphCommonClock_Config();
/* Initialize all configured peripherals */
MX_GPIO_Init();
MX_USART1_UART_Init();
MX_USB_PCD_Init();
MX_DMA_Init();
MX_SAI1_Init();
PDM_FilterHandler.bit_order = PDM_FILTER_BIT_ORDER_MSB;
PDM_FilterHandler.endianness = PDM_FILTER_ENDIANNESS_BE;
PDM_FilterHandler.high_pass_tap = 2104533974;
PDM_FilterHandler.out_ptr_channels = 1;
PDM_FilterHandler.in_ptr_channels = 1;
PDM_FilterConfig.output_samples_number = 16;
PDM_FilterConfig.mic_gain = 24;
PDM_FilterConfig.decimation_factor = PDM_FILTER_DEC_FACTOR_64;
PDM_Filter_Init((PDM_Filter_Handler_t *)(&PDM_FilterHandler));
PDM_Filter_setConfig((PDM_Filter_Handler_t *)&PDM_FilterHandler, &PDM_FilterConfig);
uint16_t pcm_data[4096];
uint16_t mid_Buffer[16];
uint16_t pcm_index = 0;
HAL_SAI_Receive_DMA(&hsai_BlockA1, &PDM_Buffer[0], 64);
while (1)
{
if (rxstate==1){
PDM_Filter(&PDM_Buffer[0], &mid_Buffer[0], &PDM_FilterHandler);
for(uint8_t i = 0; i < 64 ; i++){
pcm_data[pcm_index] = mid_Buffer[i];
pcm_index++;
}
rxstate=0;
}
if (rxstate==2){
PDM_Filter(&PDM_Buffer[64], &mid_Buffer[0], &PDM_FilterHandler);
for(uint8_t i = 0; i < 64 ; i++){
pcm_data[pcm_index] = mid_Buffer[i];
pcm_index++;
}
rxstate=0;
}
if(pcm_index==4096){
HAL_SAI_DMAPause(&hsai_BlockA1);
//pcm_index = 0;
}
}
}
void HAL_SAI_RxHalfCpltCallback(SAI_HandleTypeDef *hsai_BlockA1){
rxstate = 1;
}
void HAL_SAI_RxCpltCallback(SAI_HandleTypeDef *hsai_BlockA1){
rxstate = 2;
}
void SystemClock_Config(void)
{
...
}
void PeriphCommonClock_Config(void)
{
RCC_PeriphCLKInitTypeDef PeriphClkInitStruct = {0};
/** Initializes the peripherals clock
*/
PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_SMPS;
PeriphClkInitStruct.SmpsClockSelection = RCC_SMPSCLKSOURCE_HSI;
PeriphClkInitStruct.SmpsDivSelection = RCC_SMPSCLKDIV_RANGE0;
if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInitStruct) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN Smps */
/* USER CODE END Smps */
}
/**
* @brief SAI1 Initialization Function
* @param None
* @retval None
*/
static void MX_SAI1_Init(void)
{
/* USER CODE BEGIN SAI1_Init 0 */
/* USER CODE END SAI1_Init 0 */
/* USER CODE BEGIN SAI1_Init 1 */
/* USER CODE END SAI1_Init 1 */
hsai_BlockA1.Instance = SAI1_Block_A;
hsai_BlockA1.Init.Protocol = SAI_FREE_PROTOCOL;
hsai_BlockA1.Init.AudioMode = SAI_MODEMASTER_RX;
hsai_BlockA1.Init.DataSize = SAI_DATASIZE_16;
hsai_BlockA1.Init.FirstBit = SAI_FIRSTBIT_LSB;
hsai_BlockA1.Init.ClockStrobing = SAI_CLOCKSTROBING_FALLINGEDGE;
hsai_BlockA1.Init.Synchro = SAI_ASYNCHRONOUS;
hsai_BlockA1.Init.OutputDrive = SAI_OUTPUTDRIVE_DISABLE;
hsai_BlockA1.Init.NoDivider = SAI_MASTERDIVIDER_DISABLE;
hsai_BlockA1.Init.MckOverSampling = SAI_MCK_OVERSAMPLING_DISABLE;
hsai_BlockA1.Init.FIFOThreshold = SAI_FIFOTHRESHOLD_EMPTY;
hsai_BlockA1.Init.AudioFrequency = SAI_AUDIO_FREQUENCY_48K;
hsai_BlockA1.Init.MonoStereoMode = SAI_STEREOMODE;
hsai_BlockA1.Init.CompandingMode = SAI_NOCOMPANDING;
hsai_BlockA1.Init.PdmInit.Activation = ENABLE;
hsai_BlockA1.Init.PdmInit.MicPairsNbr = 1;
hsai_BlockA1.Init.PdmInit.ClockEnable = SAI_PDM_CLOCK1_ENABLE;
hsai_BlockA1.FrameInit.FrameLength = 16;
hsai_BlockA1.FrameInit.ActiveFrameLength = 1;
hsai_BlockA1.FrameInit.FSDefinition = SAI_FS_STARTFRAME;
hsai_BlockA1.FrameInit.FSPolarity = SAI_FS_ACTIVE_HIGH;
hsai_BlockA1.FrameInit.FSOffset = SAI_FS_FIRSTBIT;
hsai_BlockA1.SlotInit.FirstBitOffset = 0;
hsai_BlockA1.SlotInit.SlotSize = SAI_SLOTSIZE_DATASIZE;
hsai_BlockA1.SlotInit.SlotNumber = 1;
hsai_BlockA1.SlotInit.SlotActive = 0x0000FFFF;
if (HAL_SAI_Init(&hsai_BlockA1) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN SAI1_Init 2 */
/* USER CODE END SAI1_Init 2 */
}TL DR : Using this : PDM_Filter(&PDM_Buffer[0], &mid_Buffer[0], &PDM_FilterHandler); mid_buffer is stuck to 0 and I don't understand where the problem comes from
