[STM32H5] ADC clock configuration for different ADCs

[Anusha]

Hi,

I am using both ADC1 and ADC2 for my project. I want both the ADCs to be configured with different Prescalar .

But by doing so I am observing ADC2 working with the ADC1 Prescalar. Why am I facing this issue?

Is it possible to configure both the ADCs with different Prescalar?

Thankyou

[SofLit]

Hello,

You need to provide more details: 

The exact MCU part number.

A screenshot of the issue or the code or what else showing it.

[Anusha]

Hi,

I am using STM32H563VIT6 board. 

ADC configuration used for ADC1 :

hadc1.Instance = ADC1;

hadc1.Init.ClockPrescaler = ADC_CLOCK_ASYNC_DIV8;

hadc1.Init.Resolution = ADC_RESOLUTION_12B;

hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;

hadc1.Init.ScanConvMode = ADC_SCAN_ENABLE;

hadc1.Init.EOCSelection = ADC_EOC_SEQ_CONV;

hadc1.Init.LowPowerAutoWait = DISABLE;

hadc1.Init.ContinuousConvMode = ENABLE;

hadc1.Init.NbrOfConversion = 6;

hadc1.Init.DiscontinuousConvMode = DISABLE;

hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;

hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;

hadc1.Init.DMAContinuousRequests = DISABLE;

hadc1.Init.SamplingMode = ADC_SAMPLING_MODE_NORMAL;

hadc1.Init.Overrun = ADC_OVR_DATA_PRESERVED;

hadc1.Init.OversamplingMode = DISABLE;

if (HAL_ADC_Init(&hadc1) != HAL_OK)

Error_Handler();

Configuration used for ADC2:

hadc2.Instance = ADC2;

hadc2.Init.ClockPrescaler = ADC_CLOCK_ASYNC_DIV256;

hadc2.Init.Resolution = ADC_RESOLUTION_12B;

hadc2.Init.DataAlign = ADC_DATAALIGN_RIGHT;

hadc2.Init.ScanConvMode = ADC_SCAN_ENABLE;

hadc2.Init.EOCSelection = ADC_EOC_SINGLE_CONV;

hadc2.Init.LowPowerAutoWait = DISABLE;

hadc2.Init.ContinuousConvMode = ENABLE;

hadc2.Init.NbrOfConversion = 2;

hadc2.Init.DiscontinuousConvMode = DISABLE;

hadc2.Init.ExternalTrigConv = ADC_SOFTWARE_START;

hadc2.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;

hadc2.Init.DMAContinuousRequests = ENABLE;

hadc2.Init.SamplingMode = ADC_SAMPLING_MODE_NORMAL;

hadc2.Init.Overrun = ADC_OVR_DATA_PRESERVED;

hadc2.Init.OversamplingMode = DISABLE;

if (HAL_ADC_Init(&hadc2) != HAL_OK)

Error_Handler();

The ADC clock selected is HCLK which is 240Mhz.

Therefore for for ADC1 clock should be (240/8)MHz.

for ADC2 it should be (240/256)MHz.

Both the ADC is configured in DMA mode hence if I do a timing measurement of ADC data collection
both ADC1 and ADC2 is configured at (240/8)Mhz.

WHY???

Can 2 ADC be configured with different prescalar??

[SofLit]

Hello,

I think it's linked to this constraint on ADC clocks (from RM0481):

So you can't set different prescalers for different ADCs. 

[AScha.3]

Hi,

see from rm:  clock/divider -> serving both ADC analog blocks