Sampling Frequency of ADC on STM32F4 Discovery

[kyaw]

Posted on November 07, 2015 at 11:42

Hi. I'm fairly new to the concepts of ADC and currently, I'm using STM32F4 Discovery. For ADC, I have these settings for my ADC settings in my ADC_init() (source codes from an author online).

ADC_CommonInitStruct.ADC_DMAAccessMode = ADC_DMAAccessMode_Disabled; ADC_CommonInitStruct.ADC_Mode = ADC_Mode_Independent; ADC_CommonInitStruct.ADC_Prescaler = ADC_Prescaler_Div4; ADC_CommonInitStruct.ADC_TwoSamplingDelay = ADC_TwoSamplingDelay_5Cycles; ADC_CommonInit(&ADC_CommonInitStruct);and my ADC channel config is:ADC_RegularChannelConfig(ADC1, channel, 1, ADC_SampleTime_15Cycles);How do I calculate sampling frequency of my ADC from these values? #adc #adc-sampling-rate #stm32f4-discovery

[Tesla DeLorean]

Posted on November 07, 2015 at 15:39

For 12-bit sampling

SAMPFREQ = (APBFREQ / 4) / (12 + 15)

[kyaw]

Posted on November 08, 2015 at 04:13

Hi. May I know what APBFREQ is and where I can find its set value?

[Tesla DeLorean]

Posted on November 08, 2015 at 16:53

The speed the APB (peripheral bus) to which the ADC is connected. So on the F4, APB2, probably 84 MHz depending on how you have configured it.

{  RCC_ClocksTypeDef  RCC_ClockFreq;

  RCC_GetClocksFreq(&RCC_ClockFreq);

  printf(''%d\n'', RCC_ClockFreq.PCLK2_Frequency);}