C program for DS18B20 of STC microcontroller

Since the speed of STC microcontroller is faster than 8051, it belongs to 1 clock/machine cycle high-speed microcontroller. The high speed is of course its advantage, but for transplanting traditional 8051 programs, it is necessary to modify the timing to realize a certain function.

The following program is a simple driver for ds18b20. It was downloaded from the Internet. After a slight modification, it was debugged in STC12C5A32S2. Finally, the temperature is read and returned as an unsigned int. The lower 12 bits are the temperature data. The actual temperature value can be obtained by performing calculations in the main program. Hehe~~

/***********ds18b20 subroutine****************************/

/***********ds18b20 delay sub-function (crystal oscillator 11.0592MHz)*******/

void delay_18B20(unsigned int i)
{
while(i--);
}

/**********ds18b20 initialization function*************************/

void Init_DS18B20(void) 
{
unsigned char x=0;
DQ = 1; //DQ reset
delay_18B20(80); //Slight delay
DQ = 0; //MCU pulls DQ low
delay_18B20(800); //Precise delay greater than 480us
DQ = 1; //Pull the bus high
delay_18B20(140);
x=DQ; delay_18B20(200);
}

/***********ds18b20 reads a byte**************/

unsigned char ReadOneChar(void)
{
uchar i=0;
uchar dat = 0;
for (i=8;i>0;i--)
{
    DQ = 0; // give pulse signal
    dat>>=1;
    DQ = 1; // give pulse signal
    if(DQ)
    dat|=0x80;
    delay_18B20(40); //40
}
   return(dat);
}

/*************ds18b20 writes a byte****************/

void WriteOneChar(uchar dat)
{
   unsigned char i=0;
   for (i=8; i>0; i--)
   {
   DQ = 0;
    DQ = dat&0x01;
    delay_18B20(50); //50
    DQ = 1;
    dat>>=1;
}
}

/**************Read the current temperature of ds18b20************/

unsigned int ReadTemp(void)
{
unsigned char a=0;
unsigned char b=0;
unsigned int temp_value=0;

Init_DS18B20();
WriteOneChar(0xCC);     

WriteOneChar(0x44);  

delay_18B20(1000);      

Init_DS18B20();
WriteOneChar(0xCC);  
WriteOneChar(0xBE);  

delay_18B20(1000);

a=ReadOneChar(); //Read the low bit of the temperature value
b=ReadOneChar(); //Read the high bit of the temperature value

temp_value = b<<8;
temp_value |= a; 
return temp_value;
        
}