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Capturing values in ultrasonic sensor using lpc2148

Started by akashh 3 years ago3 replieslatest reply 3 years ago466 views

Hi everyone, I'm trying to capture the value to determine the distance of an object using ultrasonic sensor,but getting the distance as 0 on lcd, checked the status of trigger pin in oscilloscope getting the pulse in this pin but not on echo pin.

Assigned Trigger as Output & Echo as Input, below is the code:

Connected  ECHO_PIN to PIN 16 & TRIGGER_PIN to PIN 12

uC: LPC2148
Compiler : Keil uvision 5.1

Pclk: 60Mhz

#include<LPC214x.h>
#include<stdio.h>
#include "lcd.h"

#define PRESCALE 60
#define TIMER_TICK_1_MS (59999) /* VPB at 60 MHz clock */

#define ECHO_PIN (1 << 16)     //INPUT PIN[PIN 16]
#define TRIGGER_PIN (1 << 17)  //OUTPUT PIN[PIN 12]

void initTimer(void);
void delay3(int);
unsigned char buf[16] = {0};
void delay_ms(unsigned int count);


void initTimer()
{

 T1TCR = 0x00;  /* ensure timer 1 is off */
 /* set timer counter and prescale counter */
 T1TC = 0x0;
 T1PC = 0x0;

 /* set prescale and match values to give 1 ms "tick" */
 T1PR = 0x0;
 T1MR0 = TIMER_TICK_1_MS;

 /* set control to interrupt on MR0 match, and reset to 0 (i.e. "tick") */
 T1MCR = 0x3;

 /* go start timer 1... */
 T1TCR = 0x1;

}

void delay_ms(unsigned int count)
{
  unsigned int j=0,i=0;
  for(j=0;j<count;j++)
  {
    for(i=0;i<3000;i++);
  }
}

int main()
{
init_lcd();

IO1DIR &= ~(1<<16); //Echo pin
IO1DIR |= (1<<17); //trigger pin

initTimer();
lcd_clear();

        while(1)
        {
    long time,dist;
               

    IO1SET = 1<<17; //send high on trigger pin

    delay_ms(1000); //delay for 10us
    IO1CLR = 1<<17; // send low after 10us

    T1TCR = 0x01;  //Enable Timer1
    if(T1CR0 == 0)
    {
    delay_ms(100);
    } //wait for rising edge to occur on echo pin
    delay_ms(3);          //wait for debounce
    if(T1CR0 == 0)
    {
    time = T1CR0; //read value of CR0 reg
    dist = (time*340)/2; //dist in meters
    IO1SET = 1<<16;
    delay_ms(100);
    IO1CLR = 1<<16;
    sprintf((char *)buf, "dist:%d cm",dist);
    lcd_putstring(1, (char *)buf);
    }
     else

    T1TCR = 0x00; //disable Timer1

        }
    
}


Thank you,

Akashh




[ - ]
Reply by janneJuly 8, 2017

Why don't you get a pulse on the echo pin?

Is the trigger pulse within specification?

Have you understood your sensor?


[ - ]
Reply by akashhJuly 10, 2017

Thank you for the response sir, and have referred the working principle 

of sensor, will work on the echo pin.



[ - ]
Reply by SpiderKennyJuly 10, 2017

>>delay_ms(1000); //delay for 10us

That is not a 10 us delay - that would be 1 second!