STM32F091 ADC DMA problem

[JuM]

Problem with ADC reading at 100 kHz via DMA.

MCU runs @ 48 MHz, ADC @ 14 MHz. Configured via CubeMX.

Trying to read one ADC channel (1.5 cycles), triggered by Timer 15 (100 kHz) using HAL.

Cannot reach 100 kHz (see pictures)​. Blue are DMA interrupts (half=rising, complete=falling edge), yellow is Timer 15 interrupt (toggle).

First step with this one line Timer15 ISR:

void TIM15_IRQHandler(void) {

   HAL_GPIO_TogglePin (GPIOC, GPIO_PIN_8);

}

Rem.: 100 kHz ok.

Then add call to HAL_ADC_Start_DMA ()

void TIM15_IRQHandler(void){

   HAL_GPIO_TogglePin (GPIOC, GPIO_PIN_8);

   HAL_ADC_Start_DMA (&hadc, adc32_dma, 1);

}

Rem.: Timer frequency dropped to 56.2 kHz…

Rem.: DMA needs 4.4 µsec (incl. 1.6 µsec for DMA ISRs), not 1/2.6 µsec…

What goes wrong here?

[JuM]

[JuM]

[T J]

You dont want to do this:

 void TIM15_IRQHandler(void){
 
   HAL_GPIO_TogglePin (GPIOC, GPIO_PIN_8);
 
   HAL_ADC_Start_DMA (&hadc, adc32_dma, 1);
 
}

this is 100KHz of 5uSeconds delay you only have 10uS in 100KHz...

I run this line Once on startup, and never again:

    MAIN:
 
    ADC_RowCounter = 0;  // gather 16 rows of data
    Ave_ADC_ChannelCounter = 0;
    ADC_ChannelsCounter = ADC_ChannelCount;  // 15 ADC channels
    HAL_ADC_Start_DMA(&hadc, (uint32_t *)ADC_DMABuffer, ADC_ChannelCount); 
 
while(1){
...

[Tesla DeLorean]

>>What goes wrong here?

Decimate the interrupt loading, buffer 10 samples via DMA