In input capture function , i am trying to interface HC-sr04 Ultrasonic sensor to STM32F401. I am giving input to TRIG pin with 10 micro seconds ON and Need to Measure Pulse from ECHO pin of the Sensor and not getting Exact Width.
The Pulse width value of the waveform in input capture is not matching with orginal Pulse from sensor output .
Please help.
#include<NEW.h>
#include<stdio.h>
#include<stdarg.h>
void Ultra_setting();
void delay(int val);
void Tim3_Capture();
void Uart1_config();
void uart_printf(const char *fmt, ...);
uint32_t timeStamp1 = 0,timeStamp2=0,width=0,Distance=0;
unsigned int flag=0;
void TIM3_IRQHandler()
{
uint32_t time = TIM3->CCR1;
if (flag==0)
{
timeStamp1=time;
}
else
{
timeStamp2= time;
if(timeStamp2>timeStamp1)
{
width= timeStamp2-timeStamp1;
}
else if(timeStamp2<timeStamp1)
{
width= (0xffff - timeStamp1) + timeStamp2;
}
Distance = width *(.034/2);
flag=0;
WRITE(NVIC_ISER0 ,(0<<29));/*Disabling TIM3 Interrupt */
TIM3->CR1=0;/*Disable Counter */
uart_printf("The distance is %d %d %d %d\n", Distance,timeStamp1,timeStamp2,width);
}
flag++;
}
int main()
{
//GPIO A configuration
SystemInit();
Ultra_setting();
Uart1_config();
Tim3_Capture();/*Enable Tim3 capture*/
GPIOA->ODR |=1<<12;/* Turning ON PA12pin */
delay(100);/* 10 microseconds ON*/
GPIOA->ODR &=~(1<<12);/* Turning ON PA12 pin */
while(1);
}
char buf[512];
void uart_printf(const char *fmt, ...)
{
int ret;
va_list args;
va_start(args, fmt);
ret = vsnprintf(buf, 512, fmt, args);
va_end(args);
if (ret > 0)
{
for (int i =0; i < ret; i++)
{
USART1->SR = 0;
USART1->DR = buf[i];
while(!(USART1->SR & (1<<6)) );
}
}
}
void Uart1_config()
{
RCC->APB2ENR |=USART1_CLK;
RCC->AHB1ENR |=1;
GPIOA->MODER |=2<<18;/* Enabling Mode of PA9 */
GPIOA->MODER |=2<<20;/*Enabling Mode of PA9 */
GPIOA->OSPEEDR |=3<<18;/* Enabling High speed of PA9*/
GPIOA->OSPEEDR |=3<<20;/* Enabling High speed of PA10*/
GPIOA->AFR[1] |=7<<4;/*Enabling AFR7 of PA9 */
GPIOA->AFR[1] |=7<<8;/*Enabling AFR8 of PA10 */
USART1->CR1 |=USART1_EN;
USART1->BRR =((3<<0) | (0x68<<4)); /*9600 Baud Rate*/
USART1->CR1 |=USART1_RE;
USART1->CR1 |=USART1_TE;
}
void Tim3_Capture()
{
//input capture mode
RCC->APB1ENR |= 2; //ENABLE TIMER 3
TIM3->PSC = 16; /*divide by 16 - 1 Mhz*/
TIM3->CCMR1 |=TIM2_CCIS;//01: CC1 channel is configured as input, IC1 is mapped on TI1.
TIM3->CCER |=1; //enable CH1 input capture
TIM3->CCER |=5<<1; //enable 11: noninverted/both edges
WRITE(NVIC_ISER0 ,(1<<29));//Enable timer Interrupt.
TIM3->DIER =1<<1; //Bit 1 CC1IE: Capture/Compare 1 interrupt enable
TIM3->CR1 = 1; //enable TIM3
TIM3->CNT=0;
}
void Ultra_setting()
{
RCC->AHB1ENR |=1; /* Enabling clock for GPIOA port*/
GPIOA->MODER |=2<<12;/*Alternative function in PA6 pORT*/
GPIOA->MODER |=1<<24;/*General Purpose output function in PA12 Port*/
GPIOA->AFR[0]|=2<<24; /* Alternate function low register is AF1 is TIM3_CH1 */
GPIOA->OSPEEDR|=1<<12;/*Medium speed */
}
void delay(int val)
{
RCC->APB1ENR |=1<<0; /* TIM2 clock enabled*/
TIM2->CNT=0;
TIM2->PSC=1;
TIM2->CR1 |=1;
while(TIM2->CNT < val);
TIM2->SR=0;
}