Nucleo F401RE ADC sampling Time

Question

I would like to know how many samples I have per second for the ADC and what is its maximum samples per second and can I achieve a sample per 1 µs?

Clock : 84 Mhz

The board is Nucleo F401RE

Here is the ADC configuration with DMA :

 void ConfigureDMA_ADC() {
 __DMA2_CLK_ENABLE()
;
g_DmaHandle.Instance = DMA2_Stream4;

g_DmaHandle.Init.Channel = DMA_CHANNEL_0;
g_DmaHandle.Init.Direction = DMA_PERIPH_TO_MEMORY;
g_DmaHandle.Init.PeriphInc = DMA_PINC_DISABLE;
g_DmaHandle.Init.MemInc = DMA_MINC_ENABLE;
g_DmaHandle.Init.PeriphDataAlignment = DMA_PDATAALIGN_WORD;
g_DmaHandle.Init.MemDataAlignment = DMA_MDATAALIGN_WORD;
g_DmaHandle.Init.Mode = DMA_CIRCULAR;
g_DmaHandle.Init.Priority = DMA_PRIORITY_HIGH;
g_DmaHandle.Init.FIFOMode = DMA_FIFOMODE_DISABLE;
g_DmaHandle.Init.FIFOThreshold = DMA_FIFO_THRESHOLD_HALFFULL;
g_DmaHandle.Init.MemBurst = DMA_MBURST_SINGLE;
g_DmaHandle.Init.PeriphBurst = DMA_PBURST_SINGLE;

HAL_DMA_Init(&g_DmaHandle);

__HAL_LINKDMA(&g_AdcHandle, DMA_Handle, g_DmaHandle);

HAL_NVIC_SetPriority(DMA2_Stream4_IRQn, 0, 0);
HAL_NVIC_EnableIRQ(DMA2_Stream4_IRQn);
}

void ConfigureADC() {
GPIO_InitTypeDef gpioInit;

__GPIOA_CLK_ENABLE()
;
__ADC1_CLK_ENABLE()
;

gpioInit.Pin = GPIO_PIN_1;
gpioInit.Mode = GPIO_MODE_ANALOG;
gpioInit.Pull = GPIO_NOPULL;
HAL_GPIO_Init(GPIOA, &gpioInit);

HAL_NVIC_SetPriority(ADC_IRQn, 0, 0);
HAL_NVIC_EnableIRQ(ADC_IRQn);

ADC_ChannelConfTypeDef adcChannel;

g_AdcHandle.Instance = ADC1;

g_AdcHandle.Init.ClockPrescaler = ADC_CLOCKPRESCALER_PCLK_DIV2;
g_AdcHandle.Init.Resolution = ADC_RESOLUTION_12B;
g_AdcHandle.Init.ScanConvMode = DISABLE;
g_AdcHandle.Init.ContinuousConvMode = ENABLE;
g_AdcHandle.Init.DiscontinuousConvMode = DISABLE;
g_AdcHandle.Init.NbrOfDiscConversion = 0;
g_AdcHandle.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
g_AdcHandle.Init.ExternalTrigConv = ADC_EXTERNALTRIGCONV_T1_CC1;
g_AdcHandle.Init.DataAlign = ADC_DATAALIGN_RIGHT;
g_AdcHandle.Init.NbrOfConversion = 1;
g_AdcHandle.Init.DMAContinuousRequests = ENABLE;
g_AdcHandle.Init.EOCSelection = DISABLE;

HAL_ADC_Init(&g_AdcHandle);

adcChannel.Channel = ADC_CHANNEL_1;
adcChannel.Rank = 1;
adcChannel.SamplingTime = ADC_SAMPLETIME_144CYCLES;
adcChannel.Offset = 0;

if (HAL_ADC_ConfigChannel(&g_AdcHandle, &adcChannel) != HAL_OK) {
    asm("bkpt 255");
   }
}

Answer 1

The datasheet for STM32F401 says in Table 66. ADC characteristics (continued) for Sampling rate (fADC = 30 MHz, and tS = 3 ADC cycles) and 12-bit resolution Single ADC 2 Msps, so yes, it could achieve 1µs/sample.

However, that uses a sampling time of 3 ADC-clock cycles, a 30MHz ADC-clock, and relies on a relatively low impedance source (under 1k IIRC)

For an 84MHz clock, the ADC-clock will be 21MHz.
The maximum ADC-clock is 30MHz, but it is derived from the main clock by dividing by 2, 4, 6 or 8, and 4 is the smallest divider that keeps it within 30MHz.

So, it's going to get about 2/3rds of 2Msps, specifically \$2 \times 21/30 = 1.4\$Msps, which is still better than 1µs.