ADC and DAC (Bare-Metal)

Purpose

Configure ADC and DAC peripherals: channel selection, sampling times, calibration sequences, DMA circular buffers, and DAC static/dynamic output.

When to Use

Reading analog sensors (temperature, voltage)
Audio or control voltage output via DAC
Continuous sampling with DMA
Post-reset ADC calibration on STM32

Workflow

1. STM32 ADC single conversion

/* Enable ADC1 and GPIOA clock; PA0 analog mode */
ADC1->CR2 |= ADC_CR2_ADON;
for (volatile int i = 0; i < 10000; i++);  /* stabilization — RM value */

ADC1->SMPR2 |= ADC_SMPR2_SMP0_2;  /* 84 cycles sample time ch0 */
ADC1->SQR3   = 0;                 /* channel 0, 1 conversion */
ADC1->CR2   |= ADC_CR2_SWSTART;

while (!(ADC1->SR & ADC_SR_EOC))
    ;
uint16_t sample = ADC1->DR;

Run ADC_Calibration() / ADC_CR2_RSTCAL/CAL per RM on F1/F4 families.

2. DMA circular ADC

/* ADC1 → DMA2 Stream0, circular mode into buffer[64] */
/* Configure DMA: periph-to-mem, halfword, increment mem, circular */
ADC1->CR2 |= ADC_CR2_DMA | ADC_CR2_CONT;
DMA2_Stream0->CR |= DMA_SxCR_EN;

Half-transfer / transfer-complete IRQs for double buffering.

3. DAC output (STM32)

RCC->APB1ENR |= RCC_APB1ENR_DACEN;
DAC->CR |= DAC_CR_EN1;
DAC->DHR12R1 = 2048;  /* mid-scale 3.3V reference */

4. Agent usage

/adc-dac-baremetal Set up ADC1 channel 0 with DMA circular buffer

Common Problems

Symptom	Cause	Fix
Noisy readings	Short sample time	Increase SMP bits
Stuck EOC	Clock not enabled	RCC ADC enable
Wrong voltage	Vref not 3.3V	Measure VDDA; calibrate
DMA corrupt	Buffer alignment	Use `uint16_t` aligned buffer

Related Skills

skills/baremetal/dma-baremetal — ADC DMA streams
skills/baremetal/timers-pwm-baremetal — ADC external trigger
skills/baremetal/gpio-baremetal — analog pin mode