void ADC_Init (void)
{
    DEBUG("ADC GPIO init\n");
    RCC->AHBENR |= RCC_AHBENR_GPIOAEN;                /* enable periperal clock for GPIOA */
    GPIO_MODER_CLEAR(GPIOA,5);                        /* clerar PIN5 mode                    */
    GPIO_MODER_SET(GPIOA, 5, GPIO_MODER_ANALOG);    /* set PIN5 as analog input         */    

  /* Setup and initialize ADC converter                                       */

    RCC->APB2ENR |= RCC_APB2ENR_ADCEN;            /* enable periperal clock for ADC1          */
    
    DEBUG("ADC configure\n");
    ADC1->CFGR2 &= ~ADC_CFGR2_CKMODE;
    ADC1->CFGR2 = ADC_CFGR2_CKMODE_1;             /* ADC clock PCLK/4                            */
    
    ADC1->CFGR1 = 0;                            /* Clear register. 12bits bode as default    */

    ADC1->CFGR1 |= 5UL<<26;                        /* Set ADC input to input 5                 */
    ADC1->CFGR1 |= ADC_CFGR1_CONT;                /* Continues mode                             */
    
    ADC1->SMPR = 0x07;                            /* 239.5 ADC clock cycles                   */
    
    ADC1->CR |= ADC_CR_ADCAL;                    /* Enable calibration                */
    while (ADC1->CR & ADC_CR_ADCAL);
    ADC1->CR |= ADC_CR_ADEN;                    /* Enable ADC                        */
    
    while(!(ADC1->ISR & ADC_ISR_ADRDY));
    DEBUG("ADC init done\n");

    ADC1->IER |= ADC_IER_EOCIE;                    /* enable for EOC Interrupt         */
    NVIC_EnableIRQ(ADC1_COMP_IRQn);                /* enable ADC Interrupt             */

    ADC_StartCnv();
}


void ADC_StartCnv (void)
{
    ADC1->CR |= ADC_CR_ADSTART;            /* Start A/D conversion             */
}


void ADC1_COMP_IRQHandler(void) {

    if (ADC1->ISR & ADC_ISR_EOC) {            /* ADC1 EOC interrupt?                */
        AD_last = ADC1->DR;
        AD_done = 1;
        ADC1->ISR |= ADC_ISR_EOC;
    }
}

void init_ADC(void)
{
WORD val;

ADC->CCR = (1 << 22) | (1 << 23);
ADC1->CFGR2 = (2 << 30UL);

// Калибровка АЦП
ADC1->CR = 0;
ADC1->CR = (1UL << 31UL) | (1 << 0UL);
while(ADC1->CR & (1UL << 31UL));

val = ADC1->DR;

ADC1->CR = (1 << 0UL);
while(!(ADC1->ISR & (1 << 0UL)));

ADC1->ISR = (1 << 0UL);

ADC1->CFGR1 = 0;
ADC1->SMPR = (7 << 0UL);

ADC1->CHSELR = (1 << 16UL);
ADC1->CR = (1 << 2UL);

}

Запуск:

ADC1->CHSELR = (1 << adc_channels[adc_channel]);
ADC1->CR = (1 << 2UL);