T05 - ADC

Write a program for Nucleo STM32F401RE to measure voltage using ADC.

1. See template, how to use ADC.
2. Modify template to send measured data to PC via USART.
3. Modify template to show measured value on display.

stm32-adc.pdf

Project: adc.zip

#define BIT8
#define LOSAMP
 
void initGPIO()
{
    RCC->AHB1ENR |= 0x01;
 
    /* configure PA0 as ADC_IN0 */
    GPIOA->MODER   |=  0x03;     /* analog mode */
    GPIOA->OSPEEDR |=  0x03;     /* high speed */
}
 
void initADC1()
{
    // initialize the HSI clock
    setbit(RCC->CR, 0);         // enable HSI
    while (!getbit(RCC->CR, 1));// wait until HSI stable
 
    // initialize the ADC
    setbit(RCC->APB2ENR, 8);     // enable ADC1 peripheral clock
    ADC->CCR = 0;                 // disable temperature sensor, ADC prescaler = HSI/2
    clearbit(ADC1->SQR3, 0);    // 1st conversion in regular sequence will be from channel0
    clearbit(ADC1->SQR3, 1);    // reset state - all conversions from channel0 (PA_0)
    clearbit(ADC1->SQR3, 2);    // this is just an example
    clearbit(ADC1->SQR3, 3);
    clearbit(ADC1->SQR3, 4);
#ifdef BIT12
    clearbit(ADC1->CR1, 24);     // 12-bit resolution (Tconv = 15 ADCCLK cycles)
    clearbit(ADC1->CR1, 25);    // reset state
#endif
#ifdef BIT10
    setbit(ADC1->CR1, 24);        // 10-bit resolution (Tconv = 13 ADCCLK cycles)
#endif
#ifdef BIT8
    setbit(ADC1->CR1, 25);         // 8-bit resolution (Tconv =  11 ADCCLK cycles)
#endif
    clearbit(ADC1->CR2, 11);     // right alignment, reset state
#ifdef LOSAMP
    clearbit(ADC1->SMPR2, 0);    // channel0 sample rate: 3 cycles
    clearbit(ADC1->SMPR2, 1);    // reset state
    clearbit(ADC1->SMPR2, 2);
#endif
#ifdef HISAMP
    setbit(ADC1->SMPR2, 0);     // channel0 sample rate: 480 cycles
    setbit(ADC1->SMPR2, 1);
    setbit(ADC1->SMPR2, 2);
#endif
    setbit(ADC1->CR2, 0); // enable the ADC
}
 
void delay(int x)
{
    volatile int i;
    for (i = 0; i < 1000*x; i++);
}
 
int main()
{
    int i = 0;
 
    initGPIO();
    initADC1();
 
    while(1)
    {
        // single conversion mode, sec. 11.3.4 in RM (p. 841)
        setbit(ADC1->CR2, 30);             // software ADC start
        while (!getbit(ADC1->SR, 1));     // wait until conversion end
        i = ADC1->DR;
        delay(10);
    }
}