File content as of revision 0:32705e4af4b9:

#include <L298_H.h>
#include <mbed.h>
Ticker tic;
Timer t1;      //Timer used to record the time duration
DigitalOut trigpin(E2);
DigitalIn echopin(E3);
DigitalOut trigpin2(E4);
DigitalIn echopin2(E5);
bool dirL;
bool dirR;
float speed;
bool echo_flag;

int getDis (DigitalIn echopin) {
Timer t;
int distance;
float duration;
while (!echopin);         // read the duration time
    t.start();
    while (echopin);
    t.stop();
    duration = t.read_us(); 
    distance = (duration/2) / 29.1;  
    t.reset();
    //printf("distance: %d\n",distance); //read the distance
    return distance;
}

void inter_r(){
    echo_flag=1;
    }

int main() {
L298 controlLeft(PTA12,PTA4,PTA5);
L298 controlRight(PTA13,PTD5,PTD0);
dirR=1;
dirL=1;
speed=0.2;
int distance;
int distance2;
int totalT;
controlLeft.SetDirection(dirL);
controlRight.SetDirection(dirR);
controlLeft.SetSpeed(speed);
controlRight.SetSpeed(speed);
tic.attach(&inter_r,1.0);// call the function every 1 second
  while (1) {
    if(echo_flag == true){
    __disable_irq(); 
    t1.start();   //t1 used to indicate the total time of this code
    //Trig sensor 1 
    distance = 0;
    trigpin = 0; 
    wait_us(2);
    trigpin = 1;
    wait_us(10);
    trigpin = 0; 
    distance = getDis(echopin);
    //Trig sensor 2   
    distance2=0;
    trigpin2 = 0;
    wait_us(2);
    trigpin2 = 1;
    wait_us(10);
    trigpin2 = 0;
    distance2 = getDis(echopin2);
    
    __enable_irq(); 
        
    if (distance < 20|| distance2 <20) { 
      speed = 0;
      controlLeft.SetSpeed(speed);
      controlRight.SetSpeed(speed);
      if (distance>distance2){
          dirR=1;
          dirL=0;
          controlLeft.SetDirection(dirL);
          controlRight.SetDirection(dirR);   //obstacle on the right, turn left
          speed = 0.2;
          controlLeft.SetSpeed(speed);
          controlRight.SetSpeed(speed);
          }
      else {                 //obstacle on the left or in the middle, turn right
          dirR=0;
          dirL=1;          
          controlLeft.SetDirection(dirL);
          controlRight.SetDirection(dirR);
          speed = 0.2;
          controlLeft.SetSpeed(speed);
          controlRight.SetSpeed(speed);
          }
    }
    else {
      dirR=1;
      dirL=1;
      controlLeft.SetDirection(dirL);
      controlRight.SetDirection(dirR);
      speed = 0.2;
      controlLeft.SetSpeed(speed);
      controlRight.SetSpeed(speed);
    }
    t1.stop();
    totalT= t1.read_us();
    //printf("totalTime: %d \n",totalT);
    t1.reset();
    echo_flag=0;
    }
}
}