Question about my code to get data from PDM microphone and convert it to PCM

[EEnco.1]

I'm trying to get data from PDM microphone and convert it to PCM data. This is my first project on stm32 and I'm starting to debug the project. Could you take a quick look at my code and say if you notice something wrong ? Some part of the code come from other project that have been shared here.

#include "main.h"
 
#include "pdm2pcm_glo.h"
 
#include "stdio.h"
 
 
 
/* Private variables ---------------------------------------------------------*/
 
 SAI_HandleTypeDef hsai_BlockA1;
 
DMA_HandleTypeDef hdma_sai1_a;
 
 
 
UART_HandleTypeDef huart1;
 
 
 
PCD_HandleTypeDef hpcd_USB_FS;
 
 
 
/* 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);
 
 
 
/* Private user code ---------------------------------------------------------*/
 
/* USER CODE BEGIN 0 */
 
uint8_t rxstate = 0;
 
 
 
/* PDM-PCM conversion configuration */
 
PDM_Filter_Handler_t PDM_FilterHandler;
 
PDM_Filter_Config_t  PDM_FilterConfig;
 
 
 
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_LSB;
 
 PDM_FilterHandler.endianness = PDM_FILTER_ENDIANNESS_BE;
 
 PDM_FilterHandler.high_pass_tap = 2122358088;
 
 PDM_FilterHandler.out_ptr_channels = 1;
 
 PDM_FilterHandler.in_ptr_channels = 1;
 
 
 
 PDM_FilterConfig.output_samples_number = 64;
 
 PDM_FilterConfig.mic_gain = 1;
 
 
 
 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 PDM_Buffer[128];
 
 uint16_t pcm_data[4096];
 
 uint16_t mid_Buffer[64];
 
 //pcm_index = 0;
 
 uint8_t pcm_index = 0;
 
 
 
 HAL_SAI_DMAResume(&hsai_BlockA1);
 
 HAL_SAI_Receive_DMA(&hsai_BlockA1, PDM_Buffer, 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;
 
}

Update : Some parts of the code work not like I was expecting. About PDM_Buffer, only PDM_Buffer[0] gets a moving value : most of the time 0, sometime 7, sometime 64. All the other cases are stuck to 0. I don't know why this is happening.

[EEnco.1]

I'm testing this code and so far, I can't get the PDM data into PDM_Buffer.

[Eleon BORLINI]

Hi @EEnco.1​ ,

Can we close also the current topic, referring to this other thread?

Could you share here on the Community the solution you found to this issue?

-Eleon

[EEnco.1 · Accepted solution]

Yes you can close the current topic as well. For the code, I took one from this link https://github.com/YetAnotherElectronicsChannel/STM32_PDM_Microphone/blob/master/code/Src/main.c#L200 and modified so it works as I intended.