[SOLVED] Ds1820+PIC18f452+Hyperterminal----- Problem

[abdul991]

I'm using mplab -pickit 2 for programing single Ds1820+PIC18f452+Hyperterminal. I'm new to this 1-wire concept.
The problem is i'm unable to receive the output-low presence pulse after i send reset pulse for more than 480usec to the ds1820

This is my code. Please help. i'm doing my engg. project

while(1)
   { 
    
    DS1820_DelayUs(10000);
       
    serialSend1(resetTx());serial Transmit
           
   }

bool input_func(void)
{
    TRISBbits.TRISB3 = 1;     
    return PORTBbits.RB3;
}

bool resetTx()
{
   bool bPresPulse;
   
   TRISBbits.TRISB3 = 0;
   PORTBbits.RB3 = 0                 
   DS1820_DelayUs(500);
   serialSendRst(input_func());   // serial Transmit 
   DS1820_DelayUs(40);

   /* get presence pulse */
   
   DS1820_DelayUs(100);
   bPresPulse = input_func();
   
   return bPresPulse;
}


// 12Mhz clock = > ( 1/12M)secs  per clock cycle.
// 1 inst = 4 clock cycle = 4*1/12M = 0.333 usec

// 1usec delay = 1/.333 = 3


void DS1820_DelayUs(long delayUs)
{
int i,j;
for (i=0;i<delayUs;i++)
for (j=0;j<3;j++);
}

 

[abdul991]

i've somehow understood the problem is with the delay......

so i altered the code but the result is...... pr= 1 pr= 1 pr= 1..... i should have got pr=1 pr=0.... continuously... at Hyperterminal

 #define input(pin)   input_func()  // <----this func is defined in previous post
#define output_low(pin)     TRISBbits.TRISB3 = 0;PORTBbits.RB3 = 0
main(){
while(1)

    DS1820_DelayMs(1000);
    serialSendRst(input(pin));    
    DS1820_DelayMs(1000);
    serialSendRst(resetTx());
          
   }
}
              
/***************************************************/

/*

The bus master transmits (TX) a reset pulse (a low signal
for a minimum of 480 usec). The bus master then
releases the line and goes into a receive mode (RX).
The 1–Wire bus is pulled to a high state via the 5K
pull–up resistor . After detecting the rising edge on the
I/O pin, the DS1820 waits 15–60 usec and then transmits
the presence pulse (a low signal for 60–240 usec).

*/

bool resetTx()
{
   bool bPresPulse;
   
   output_low(pin);                 
   DS1820_DelayUs(24);    //24*20usec = 480
 
   bPresPulse = input(pin);
                             // uses 15 + serTx baudrate delay
   DS1820_DelayUs(5);
   /* get presence pulse */
   
   bPresPulse = input(pin);
   
   return bPresPulse;

}

/****************************************************/

// 12Mhz = > ( 1/12M) sec per clock cycle.
// 1 inst = 4 clock cycle = 4*1/12M = 0.333 usec

// 1usec delay = 1/.333 = 3

// As per Modified-Delay :- 1 delayUs =  6.66usec *3 Inst  =  20 useconds.

void DS1820_DelayUs(long delayUs)
{
int i,j;
for (i=0;i<delayUs;i++)
for (j=0;j<3;j++);
}

/****************************************************/