Why Can't My DS18B20 Always Initialize?

// Delay 2 microseconds subroutine (12MHZ)

void delay_2us (unsigned char i)

{while (-i);}

void init_ds18b20 ()

{

uchar x = 0;

DQ = 1; / * First pull high to prepare for reset * /

delay_2us (24); / * delay it a bit * /

DQ = 0; / * pull the level low, delay at least 480us * /

delay_2us (240); / * Delay here 480us * /

DQ = 1; / * After the reset signal is given, pull the level high and wait for the existence pulse * /

delay_2us (30); / * Delay 15 ~ 60us, here delay 60us, give the existence pulse time * /

x = DQ; / * Read existence pulse * /

delay_2us (240); / * Read the presence pulse, the low-level signal whose presence pulse is at least 60us to 240us, here 480us * /

while (1)

{

if (x == 1)

display (1,1,1,1); Initialization failed to display 1111

else

display (0,0,0,0); // Display 0000 after initialization

}

DQ = 1; / * After reading, the signal is reset, DS18B20 is initialized, and data exchange protocol is generated * /

}

After tuning for a long time, it still shows 1111.

What is the reason?