Pulse Density Modulation Interface

[polotomino]

Hi!

I'm trying to enable the PDM interface on a STM32WB55RGV with one microphone. Basically i followed the AN5027 application note, but I'm not able to start the clock on the proper GPIO.

The configuration from CUBE-MX seems ok, and I checked the registers value, so maybe I'm setting up the wrong API to start the streaming.

Any advice?

	MX_SAI1_Init();
 
	osDelay(10);
 
	//HAL_SAI_Receive_DMA(&hsai_BlockA1, (uint8_t *)mic_buff, MIC_BUFF_LEN);
	HAL_SAI_Receive(&hsai_BlockA1, (uint8_t *)mic_buff, MIC_BUFF_LEN, 100);
 
 
	/* start application */
	while (1){
		osDelay(1000);
	}

[waclawek.jan]

How is SAI clock set in RCC?

Read out and check/post content of relevant RCC, SAI and GPIO registers.

JW

[polotomino]

/**
  * @brief System Clock Configuration
  * @retval None
  */
void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
  RCC_PeriphCLKInitTypeDef PeriphClkInitStruct = {0};
 
  /** Configure the main internal regulator output voltage 
  */
  __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);
  /** Initializes the CPU, AHB and APB busses clocks 
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI|RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
  RCC_OscInitStruct.PLL.PLLM = RCC_PLLM_DIV1;
  RCC_OscInitStruct.PLL.PLLN = 8;
  RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV31;
  RCC_OscInitStruct.PLL.PLLR = RCC_PLLR_DIV2;
  RCC_OscInitStruct.PLL.PLLQ = RCC_PLLQ_DIV2;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    Error_Handler();
  }
  /** Configure the SYSCLKSource, HCLK, PCLK1 and PCLK2 clocks dividers 
  */
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK4|RCC_CLOCKTYPE_HCLK2
                              |RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
  RCC_ClkInitStruct.AHBCLK2Divider = RCC_SYSCLK_DIV2;
  RCC_ClkInitStruct.AHBCLK4Divider = RCC_SYSCLK_DIV1;
 
  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_3) != HAL_OK)
  {
    Error_Handler();
  }
  /** Initializes the peripherals clocks 
  */
  PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_SMPS|RCC_PERIPHCLK_SAI1
                              |RCC_PERIPHCLK_I2C1|RCC_PERIPHCLK_I2C3
                              |RCC_PERIPHCLK_ADC;
  PeriphClkInitStruct.PLLSAI1.PLLN = 6;
  PeriphClkInitStruct.PLLSAI1.PLLP = RCC_PLLP_DIV31;
  PeriphClkInitStruct.PLLSAI1.PLLQ = RCC_PLLQ_DIV2;
  PeriphClkInitStruct.PLLSAI1.PLLR = RCC_PLLR_DIV2;
  PeriphClkInitStruct.PLLSAI1.PLLSAI1ClockOut = RCC_PLLSAI1_SAI1CLK;
  PeriphClkInitStruct.I2c1ClockSelection = RCC_I2C1CLKSOURCE_PCLK1;
  PeriphClkInitStruct.I2c3ClockSelection = RCC_I2C3CLKSOURCE_PCLK1;
  PeriphClkInitStruct.Sai1ClockSelection = RCC_SAI1CLKSOURCE_PLLSAI1;
  PeriphClkInitStruct.AdcClockSelection = RCC_ADCCLKSOURCE_PLL;
  PeriphClkInitStruct.SmpsClockSelection = RCC_SMPSCLKSOURCE_HSI;
  PeriphClkInitStruct.SmpsDivSelection = RCC_SMPSCLKDIV_RANGE1;
 
  if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInitStruct) != HAL_OK)
  {
    Error_Handler();
  }
}

[waclawek.jan]

I don't use Cube and don't understand its gibberish.

It appears you are using the SAI PLL's output - is that PLL running? Maybe there's no simple way to test that on your STM32 model, then use for SAI for testing a clock you are sure it's running.

Read out and check/post content of relevant RCC, SAI and GPIO registers.

JW

[polotomino]

Thank you su much.

Here the SAI registers:

The RCC :

and lastly the GPIOs configuration:

PA10 is the SAI_D1 and PA8_SAI1_CK2

[waclawek.jan]

OK and GPIO_AFRx is set to the appropriate AF?

I have no experience with SAI with PDM, so you may want to check that yourself against the RM.

Did you make sure there is a valid clock input in RCC, maybe switching to a clock source which is known working (such as the main PLL)?

JW

[polotomino · Accepted solution]

Thanks waclawek.jan 

The issue comes from the RCC, selecting the PLLP clock source instead of PLLSAI1 the PDM peripheral works. It seems an CUBEMX bug generating the RCC config function.

[waclawek.jan]

OK so problem solved? Then please select your post as "Best" to mark the thread as solved.

JW

@Imen DAHMEN​  - so this appears that CubeMX does not generate code for initializing the PLLSAI for the 'WB55, can this please be checked?

[Khouloud ZEMMELI]

​Hello @Community member​  Did you mean by "  CubeMX does not generate code for initializing the PLLSAI for the 'WB55" that there's a missed  line of code ?

Thanks,

Khouloud

[Khouloud ZEMMELI]

​and if yes which lignes of code ?

Thanks  @Community member​ 

Khouloud