Piotr Galek

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12 years, 9 months ago.

Reading data from sensors and not getting results

Hi

I am just working on line follower using LPC1768 and I have problem with driving a motor and at the same time reading sensors. With my implementation, it seems that while motors are running, reading from sensors do not change. On the other when I only implement reading sensors they work fine. Here is my code could you tell me what could be a problem. Many thanks!

#include "mbed.h"

//------MOTOR----------
I2C i2c(p9, p10);        // sda, scl

PwmOut pwm0(p22);
PwmOut pwm1(p23);

const int addr = 0x40; // define the I2C Address

DigitalOut   led(LED1);                                  // status LED
DigitalOut   test(p27);                                  // test pin

DigitalInOut ir_rx0(p11);  // IR recieves
DigitalInOut ir_rx1(p12);  // IR recieves
DigitalInOut ir_rx2(p15);  // IR recieves
DigitalInOut ir_rx3(p16);  // IR recieves
DigitalInOut ir_rx4(p17);  // IR recieves
DigitalInOut ir_rx5(p18);  // IR recieves
DigitalInOut ir_rx6(p25);  // IR recieves
DigitalInOut ir_rx7(p26);  // IR recieves

PwmOut ir_tx(p24);                                       // IR transmitter

Serial pc(USBTX, USBRX);                                 // USB serial port
 
// Black  : 4.2x200us   = 840us
// White  : 2 x 100us   = 200us
// Silver : 1.2 x 100us = 120us
          
int main() {

  bool ir_set[8];
  int  ir_value[8];
  
  int  ir_buffer;
  int  i, j, k;
   
  ir_tx.period_us(100);       // a 20ms period
  ir_tx.pulsewidth_us(100);    // 
  
  led  = 1;   
  test = 0;
  
  
  char cmd[2];
  pwm0.period_ms(50);     
  pwm0.pulsewidth_ms(5);  
    
  pwm1.period_ms(50);      
  pwm1.pulsewidth_ms(5);  

  while(true)
  {
  
    pc.printf("Drive Motor\n");
    
    cmd[0] = 0x99;           
    cmd[1] = 0x00;           
    i2c.write(addr, cmd, 1); 
    
    
    
    ir_rx0.output();
    ir_rx1.output();
    ir_rx2.output();
    ir_rx3.output(); 
    ir_rx4.output();
    ir_rx5.output();
    ir_rx6.output();
    ir_rx7.output(); 
  
    ir_rx0 = 1;
    ir_rx1 = 1;
    ir_rx2 = 1;
    ir_rx3 = 1;
    ir_rx4 = 1;
    ir_rx5 = 1;
    ir_rx6 = 1;
    ir_rx7 = 1; 
    
    for(i=0; i<8; i++)
    {
      ir_set[i]=true;
      ir_value[i]=0;
    }

    wait_us(50);
    
    ir_rx0.input(); 
    ir_rx1.input();  
    ir_rx2.input(); 
    ir_rx3.input(); 
    ir_rx4.input(); 
    ir_rx5.input();  
    ir_rx6.input(); 
    ir_rx7.input(); 
         
    test = 1;
    
    for(i=0; i<20; i++)
    {
      wait_us(50);
      
      if ((ir_buffer && 0x01) == 0)
        test = 0;
        
      if((ir_rx0==0) & ir_set[0])
      {
        ir_set[0]=false; ir_value[0]=i; 
      }  
      if((ir_rx1==0) & ir_set[1])
      {
        ir_set[1]=false; ir_value[1]=i; 
      }  
      if((ir_rx2==0) & ir_set[2])
      {
        ir_set[2]=false; ir_value[2]=i; 
      }  
      if((ir_rx3==0) & ir_set[3])
      {
        ir_set[3]=false; ir_value[3]=i; 
      }  
      if((ir_rx4==0) & ir_set[4])
      {
        ir_set[4]=false; ir_value[4]=i; 
      }  
      if((ir_rx5==0) & ir_set[5])
      {
        ir_set[5]=false; ir_value[5]=i; 
      }  
      if((ir_rx6==0) & ir_set[6])
      {
        ir_set[6]=false; ir_value[6]=i; 
      }  
      if((ir_rx7==0) & ir_set[7])
      {
        ir_set[7]=false; ir_value[7]=i; 
      }  
         
    }
    
    
    printf( "ADC conversion\n" );
    printf( "chan 0 = %d\n", ir_value[0] );  
    printf( "chan 1 = %d\n", ir_value[1] );     
    printf( "chan 2 = %d\n", ir_value[2] );  
    printf( "chan 3 = %d\n", ir_value[3] );          
    printf( "chan 4 = %d\n", ir_value[4] );  
    printf( "chan 5 = %d\n", ir_value[5] );     
    printf( "chan 6 = %d\n", ir_value[6] );  
    printf( "chan 7 = %d\n", ir_value[7] );      
      
    wait(1);

  }
}

2 Answers

Wim Huiskamp
12 years, 9 months ago.

All PWM channels (so both your motor outputs and your ir_tx) will have the same period. The last period value that you set will apply to all channels. I guess the IR receivers wont work anymore when you use the motor at 20ms because the IR transmitter is at a very low freq.

Accepted Answer
Piotr Galek
poster
12 years, 9 months ago.

Hi

I understand the problem. So what could be the possible solution? Making the period for PWM the same as IR? I have done this but this hasn't solved the problem.