/*I want to read stm32 temperature using ADC1 with timer 2 configured.
I am getting temperature reading as 60 degrees when I configured
ADC1->SQR3=16;
and -275 degrees when ADC1->SQR3=18; Is any thing wrong? */
#include "stm32f4xx.h" // Device header
#include <stdio.h>
int UART2_write(int ch);
void UART2_Init(void);
void msdelay(unsigned int delay);
int data;
double voltage;
double celsius;
struct __FILE
{
int handle;
};
FILE __stdout ={1};
int fputc(int c, FILE *f)
{
return UART2_write(c);
}
int UART2_write(int ch)
{
/*Wait till TX buffer is filled with data */
while(!(USART2->SR & 0X0080));
USART2->DR = ch;
msdelay(100);
return ch;
}
void UART2_Init(void)
{
/*Enable GPIO clock for Port A since USART2 connected to PA2*/
RCC->AHB1ENR |=1;
/*Enable bit 17 of RCC_APB1ENR for USART2 Clock */
RCC->APB1ENR |= 0X20000;
/*USART2 connected to Alternate functin AF7 low register GPIOx_AFRL AF7(AFRL2) (PA2)=0111 = 0X0700 (doubt)*/
//PA0 (0 to 3 bits)->0000, PA1 (4 TO 7 bits)-> 0000, PA2 (AFRL2)8 to 11 ->0111
GPIOA->AFR[0]= 0x0700; // 0000 0111 0000 0000
/*Set PA2 to alternate function*/
GPIOA->MODER = 0X0020;
/*set baud rate @9600*/
USART2->BRR = 0X0683;
/*Enable the USART2 module UE bit */
USART2->CR1 |= 0x2000;
/*Enable USART2 Transmitter TE bit */
USART2->CR1 |= 0X0008;
}
int main(void)
{
RCC->AHB1ENR |=1;
RCC->APB1ENR|=1;
TIM2->PSC=1600-1;
TIM2->ARR=(10000)-1;
TIM2->CCMR1=0X6800;
TIM2->CCR2=50-1;
TIM2->CCER|=0x0010;
TIM2->CNT=0;
TIM2->CR1=1;
RCC->APB2ENR|= 0x100;
ADC->CCR&=~0x00400000 ; //clear VBAT to disable
ADC->CCR |=0x00800000 ; //Temperature sensor and VREFINT enable
ADC1->SQR3=16; //select channel 16 for ADC1
//Select a sampling time 100: 84 cycles 10us
ADC1->SMPR1= 0x04000000;
//1001: Timer 2 CC2 event for regular channels
ADC1->CR2=0x13000000;
ADC1->CR2|=1; //Start ADC
UART2_Init();
printf("STM32 Temperature \r\n");
while(1)
{
while(!(ADC1->SR)){};
data=ADC1->DR;
voltage=(double)data/4095*3.3;
celsius=(voltage-0.76)/0.0025+25;
printf("%d,%.2f\370C\r\n",data,celsius);
}
}
