Need very slow ADC readings on STM32G474

[ValterMatos]

I'm using the STM32G474 at 170MHz.

Is it possible to simulate hadc1.Init.ClockPrescaler = ADC_CLOCK_ASYNC_DIV512; since the G474  only recognizes up to ADC_CLOCK_ASYNC_DIV256;

I need very slow readings from the ADC.

Thank you

Valter

[TDK]

Sure, slow down the ADC clock or use software oversampling. Note that there is a minimum FADC requirement of 140 kHz that you need to be at/above. You can use software oversampling to achieve lower effective values.

[mƎALLEm]

Hello,

Use a timer to trigger the ADC readings.

[ValterMatos]

Not yet. I've tried several programming alternatives and still haven't been able to solve it. Oversampling didn't work correctly.
I'll try a timer to trigger the ADC readings.
I need to simulate a 512 pressscaler on the ADC readings because the G474 only accepts up to 256.
I wouldn't like to reduce the clock speed.

[TDK · Accepted solution]

> Oversampling didn't work correctly.

Then you didn't do it right.

x = (x0 + x1) / 2

[MasterT]

G474 has an option to choose clock for ADC, 

  RCC_PeriphCLKInitTypeDef PeriphClkInit  = {0};

  PeriphClkInit.PeriphClockSelection      = RCC_PERIPHCLK_ADC12;
  //PeriphClkInit.Adc12ClockSelection       = RCC_ADC12CLKSOURCE_SYSCLK;
  PeriphClkInit.Adc12ClockSelection       = RCC_ADC12CLKSOURCE_PLL;

 Using PLL instead of SYSCLK allows to generate any clock, simply changing M and N PLL's settings.

I tested this mode not for lower, but higher speed, overdriving ADC up to 168 MHz. And it works.

[ValterMatos]

Very good.

I'll review the code.
Thank you for the suggestion.