Change ADC clock in STM32H7

[halbeeee]

Hello, i'm using an STM32H7 but unfortunately for a known bug of the firmware package i'm not able to select the ADC prescaler. Uprading to a newer firmware package is not considered.

At the moment i resolved applying a prescaler with the line

hadc1.Init.ClockPrescaler = ADC_CLOCK_SYNC_PCLK_DIV1;

The problem is that this only works with the synchronous clock, if i try the asynchronous clock the ADC doesn't work, like if the clock is not enabled.

My idea is that i have to enable PLL2P because is disabled, how can i do it with code since i'm not able to manage it througth cube ide?

Thank you in advice

[LCE · Accepted solution]

Find SystemClock_Config() and modify.

Here's some clock setup for a Nucleo H723, including ADC from PLL3:

But better check the values for your application.

/**
  * @brief System Clock Configuration
  * @retval None
  */
/* notes:
 *	Power:
 *		- voltage scaling for core:
 *			VOS0 ~1.36 V - "boosted performance" - highest freq -> highest power
 *			VOS1 ~1.21 V - "high performance"
 *			VOS2 ~1.10 V - "medium performance"
 *		-> in these voltage ranges SAI, I2S, OctoSPI can work with at least up to
 *			113 MHz (RM0468, pg 336)
 *
 *	PLLs:
 *		- main PLL input range: 2 .. 16 MHz
 *		- PLL2 & 3 input range: 1 ..  2 MHz
 */
void SystemClock_Config(void)
{
	RCC_OscInitTypeDef RCC_OscInitStruct = { 0 };
	RCC_ClkInitTypeDef RCC_ClkInitStruct = { 0 };
 
	/* supply configuration update enable */
	HAL_PWREx_ConfigSupply(PWR_LDO_SUPPLY);
 
	/* configure the main internal regulator output voltage */
	__HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);
 
	while( 0 == __HAL_PWR_GET_FLAG(PWR_FLAG_VOSRDY) );
 
	/* configure LSE Drive Capability */
	HAL_PWR_EnableBkUpAccess();
	__HAL_RCC_LSEDRIVE_CONFIG(RCC_LSEDRIVE_LOW);
 
	/* Macro to configure the PLL clock source */
	__HAL_RCC_PLL_PLLSOURCE_CONFIG(RCC_PLLSOURCE_HSE);
 
 
	/* initialize RCC oscillators and PLL 1 for core and peripheral busses
	 */
	RCC_OscInitStruct.OscillatorType 	= RCC_OSCILLATORTYPE_HSE | RCC_OSCILLATORTYPE_LSE;
	RCC_OscInitStruct.HSEState 			= RCC_HSE_BYPASS;
	RCC_OscInitStruct.LSEState 			= RCC_LSE_ON;
	RCC_OscInitStruct.PLL.PLLState 		= RCC_PLL_ON;
	RCC_OscInitStruct.PLL.PLLSource 	= RCC_PLLSOURCE_HSE;
 
/* NUCLEO_H723: 8.333 MHz input from ST-LINK */
	RCC_OscInitStruct.PLL.PLLM 			= 4;	/* -> 8 MHz / 4 = 2 MHz */
	RCC_OscInitStruct.PLL.PLLN 			= 192;	/* -> 400 MHz */
	RCC_OscInitStruct.PLL.PLLP 			= 1;		/* 400 MHz */
	RCC_OscInitStruct.PLL.PLLQ 			= 5;		/*  80 MHz for FDCAN */
	RCC_OscInitStruct.PLL.PLLR 			= 4;		/* 100 MHz */
	RCC_OscInitStruct.PLL.PLLRGE 		= RCC_PLL1VCIRANGE_1;
	RCC_OscInitStruct.PLL.PLLVCOSEL 	= RCC_PLL1VCOWIDE;
	RCC_OscInitStruct.PLL.PLLFRACN 		= 0;
 
	if( HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK ) Error_Handler();
 
	/** Initializes the CPU, AHB and APB buses clocks
	*/
	RCC_ClkInitStruct.ClockType 		= RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_SYSCLK
											| RCC_CLOCKTYPE_PCLK1 | RCC_CLOCKTYPE_PCLK2
											| RCC_CLOCKTYPE_D3PCLK1 | RCC_CLOCKTYPE_D1PCLK1;
	RCC_ClkInitStruct.SYSCLKSource 		= RCC_SYSCLKSOURCE_PLLCLK;
	RCC_ClkInitStruct.SYSCLKDivider 	= RCC_SYSCLK_DIV1;
	RCC_ClkInitStruct.AHBCLKDivider 	= RCC_HCLK_DIV2;
	RCC_ClkInitStruct.APB1CLKDivider 	= RCC_APB1_DIV2;
	RCC_ClkInitStruct.APB2CLKDivider 	= RCC_APB2_DIV2;
	RCC_ClkInitStruct.APB3CLKDivider 	= RCC_APB3_DIV2;
	RCC_ClkInitStruct.APB4CLKDivider 	= RCC_APB4_DIV2;
 
	if( HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK ) Error_Handler();
}
 
/**
  * @brief Peripherals Common Clock Configuration
  * @retval None
  */
void PeriphCommonClock_Config(void)
{
	RCC_PeriphCLKInitTypeDef PeriphClkInitStruct = { 0 };
 
/* NUCLEO_H723: 8.333 MHz input from ST-LINK */
 
/* PLL2: base for 400 kHz / x sampling rate */
	PeriphClkInitStruct.PLL2.PLL2M 		= 2;
	PeriphClkInitStruct.PLL2.PLL2N 		= 122;
	PeriphClkInitStruct.PLL2.PLL2P 		= 5;	/* 102.4 MHz */
	PeriphClkInitStruct.PLL2.PLL2Q 		= 5;	/* 102.4 MHz */
	PeriphClkInitStruct.PLL2.PLL2R 		= 10;	/* 51.2 MHz */
	PeriphClkInitStruct.PLL2.PLL2RGE 	= RCC_PLL2VCIRANGE_2;
	PeriphClkInitStruct.PLL2.PLL2VCOSEL = RCC_PLL2VCOWIDE;
	PeriphClkInitStruct.PLL2.PLL2FRACN 	= PLL_FRACN_BASE_8M3_51M2;
 
/* PLL3: base for 192 kHz / x sampling rate */
	PeriphClkInitStruct.PLL3.PLL3M 		= 5;
	PeriphClkInitStruct.PLL3.PLL3N 		= 235;
	PeriphClkInitStruct.PLL3.PLL3P 		= 4;	/* 98.304 MHz */
	PeriphClkInitStruct.PLL3.PLL3Q 		= 4;	/* 98.304 MHz */
	PeriphClkInitStruct.PLL3.PLL3R 		= 8;	/* 49.152 MHz */
	PeriphClkInitStruct.PLL3.PLL3RGE 	= RCC_PLL3VCIRANGE_0;
	PeriphClkInitStruct.PLL3.PLL3VCOSEL = RCC_PLL3VCOMEDIUM;
	PeriphClkInitStruct.PLL3.PLL3FRACN 	= PLL_FRACN_BASE_8M3_98M3;
 
/* SAI 1, SAI 4 */
	PeriphClkInitStruct.PeriphClockSelection |= ( RCC_PERIPHCLK_SAI1 | RCC_PERIPHCLK_SAI4A | RCC_PERIPHCLK_SAI4B );
/* SPI 1, SPI 2, SPI 6 */
	PeriphClkInitStruct.PeriphClockSelection |= ( RCC_PERIPHCLK_SPI1 | RCC_PERIPHCLK_SPI2 | RCC_PERIPHCLK_SPI6 );
 
	PeriphClkInitStruct.Sai1ClockSelection 		= RCC_SAI1CLKSOURCE_PLL2;
	PeriphClkInitStruct.Sai4AClockSelection 	= RCC_SAI4ACLKSOURCE_PLL2;
	PeriphClkInitStruct.Spi123ClockSelection 	= RCC_SPI123CLKSOURCE_PLL2;
	PeriphClkInitStruct.Spi6ClockSelection 		= RCC_SPI6CLKSOURCE_PLL2;
 
/* ADC */
	PeriphClkInitStruct.PeriphClockSelection |= RCC_PERIPHCLK_ADC;
	PeriphClkInitStruct.AdcClockSelection 	 = RCC_ADCCLKSOURCE_PLL3;
 
	if( HAL_RCCEx_PeriphCLKConfig(&PeriphClkInitStruct) != HAL_OK ) Error_Handler();
}

[halbeeee]

[]

[halbeeee]

Thank for your answer, very useful. The only question is that you told me to modify the SystemClock_Config(), but looking on your code seems like that the function that i need to modify is PeriphCommonClock_Config(), which i don't have. Is there a way to make it appear or do i need to write by hand and then call it?

[LCE]

Oops... okay, it's in RCC_PeriphCLKInitTypeDef ()

However you like, it's no big deal to integrate that into SystemClock_Config().