Điện áp analog được đưa vào chân ADC (ví dụ PA0, PA1, PA2…).

ADC 12-bit của STM32 sẽ chuyển đổi:

ADC_Value = V_in/V_ref *4095

Trong đó:

• V_in: điện áp đầu vào
• V_ref: điện áp tham chiếu (thường 3.3V)
• 4095 = 2^12-1

Ví dụ:

Vin	Giá trị ADC
0V	0
1.65V	≈2048
3.3V	4095

Code tham khảo:

#include "stm32f10x.h"                  // Device header

//#include "math.h"

uint8_t Maled[10] = {0xC0, 0xF9, 0xA4, 0xB0, 0x99, 0x92, 0x82, 0xF8, 0x80, 0x90};

uint8_t Tim2_flag=0;

uint8_t HC,HDV,so;

int count=0;

void delay();

void Tim2_Config();

void TIM2_IRQHandler(void);

void ADC_Config(void);

uint16_t ADC_Read(void);

void Tim3_Config(void);

void TIM3_IRQHandler(void);

uint16_t preset_speed;

int main(void)

{

              int count1;       

              RCC->APB2ENR |=(1<<2)|(1<<4)|(1<<3);

              GPIOA->CRL &= ~(0xff<<0);

              GPIOA->CRL |=(8<<0)|(8<<4);

              GPIOB->CRL =0;

              GPIOB->CRL |=0x33333333;

              GPIOB->CRH =0;

              GPIOB->CRH |=0x33333333;   

              GPIOA->CRL |=(8<<4);

              GPIOC->CRH  &=~(0xf<<20);

              GPIOC->CRH  |=(3<<20);

              // cau hin timer2 dinh thoi 100ms, quan ly bang ngat

                           ADC_Config();

              Tim2_Config();

              Tim3_Config();

              //HDV=3;

              while(1)

              { 

              if(GPIOA->IDR & (1<<0))

              {

                           while(GPIOA->IDR & (1<<0));

                           so++;

              //           HC=5;

                           HC=so/10;

                           HDV=so%10;                                        

              }

              if(GPIOA->IDR & (1<<1))

              {

                           while(GPIOA->IDR & (1<<1));

                           so--;

              //           HC=5;

                           HC=so/10;

                           HDV=so%10;                              

              }

              }           

}           

void delay()

{

              int i;

              for(i=0;i<1000;i++)

              {     

              }

}

void Tim2_Config()

{

              //dinh thoi 100ms

              RCC->APB1ENR |=(1<<0); //TIM1_ENABLE=1: Kích hoat Timer 2

              TIM2->PSC =8000;//Chia tan so 8 MHz xuong còn 10 kHz

              TIM2->ARR =20-1;// dinh thoi 100ms

              TIM2->DIER |= (1<<0);

              TIM2->CR1 |=(1<<0);

              NVIC_EnableIRQ(TIM2_IRQn);          // Bat ngat Timer 2

}

void TIM2_IRQHandler(void)

{

               if (TIM2->SR & 1<<0)

                            {

        TIM2->SR &= ~1<<0;          // Xóa co ngat

                                          count++;

                                           if(count==1)

                                                       {

                                                                     GPIOB->ODR &= ~(0x3ff);

                                                                     GPIOB->ODR |= (1 << 8);         // Bat hàng chuc

                                                                       GPIOB->ODR &= ~(1 << 9);

                                                                     //GPIOB->ODR |=(1<<8);

                                                                     GPIOB->ODR |=Maled[HC];

                                                                    

                                                       }

                                                       else

                                                       {

                                                                     GPIOB->ODR &= ~(0x3ff);

                                                       //              GPIOB->ODR |=(1<<9);

                                                                     GPIOB->ODR |= (1 << 9);         // Bat hàng chuc

                                                         GPIOB->ODR &= ~(1 << 8);

                                                                     GPIOB->ODR |=Maled[HDV];

                                                                     count=0;

                                                       }                                 

                            }

}

void ADC_Config(void)

{

    // Kich hoat clock cho Port A va ADC1

    RCC->APB2ENR |= (1 << 2);   // IOPAEN: Bat clock cho GPIOA

    RCC->APB2ENR |= (1 << 9);   // ADC1EN: Bat clock cho ADC1

    GPIOA->CRL &= ~(0xF << (4 * 4)); // Xoa cac bit tuong ung voi PA4

    // Cau hinh ADC

    ADC1->SQR1 &= ~(0xF << 20); 

    ADC1->SQR3 &= ~(0x1F);

    ADC1->SQR3 |= (4 << 0);

    ADC1->SMPR2 &= ~(0x7 << (3 * 4));

    ADC1->SMPR2 |= (7 << (3 * 4));

    ADC1->CR2 |= (1 << 0);       // ADON: Bat ADC1

    ADC1->CR2 |= (1 << 2);       // CAL: Bat dau hieu chuan ADC

    while (ADC1->CR2 & (1 << 2)); // Doi hieu chuan hoan tat

}

 //Ham doc gia tri ADC

uint16_t ADC_Read(void) {

    ADC1->CR2 |= (1 << 0);       // Bat ADC1 (ADON)

    ADC1->CR2 |= (1 << 22);      // SWSTART: Bat dau chuyen doi phan mem

               GPIOC->CRH |=(1<<13);

    while (!(ADC1->SR & (1 << 1)));

    return ADC1->DR;

}

void Tim3_Config(void) {

    // Kich hoat clock cho Timer 3

    RCC->APB1ENR |= (1 << 1);  // Bit 1: Kich hoat clock cho TIM3

    TIM3->PSC = 8000 ;  // Prescaler = 8000: PSC = 8000 - 1

    TIM3->ARR = 50-1; 

    // Cho phep ngat khi tran

    TIM3->DIER |= (1 << 0);  // Bit UIE: Cho phep ngat khi tran

    // Bat Timer 3

    TIM3->CR1 |= (1 << 0);    // Bit CEN: Bat Timer 3

    // Kich hoat ngat cho TIM3 trong NVIC

    NVIC_EnableIRQ(TIM3_IRQn);   // Kich hoat ngat TIM3 trong NVIC

}

void TIM3_IRQHandler(void)

{

              uint16_t adc_value;

 if (TIM3->SR & 1<<0)

               {  // Bit UIF: Kiem tra co ngat tran

                          //Tinh toan gia tri ADC

                           dc_value = ADC_Read(); // Doc gia tri ADC

                preset_speed = (adc_value * 100) / 4095;

   HC=preset_speed/10;

               HDV=preset_speed%10;

                           // HC=1;

                           // HDV=3;

                             TIM3->SR &= ~(1 << 0);  // Xoa co ngat tran

}              

}