Digital thermometer based on 51 microcontroller

Solution block diagram: Schematic design description
Power supply section:
Display section:
Temperature detection section:
Alarm circuit:
51 minimum system:
PCB design description
There is nothing particularly noteworthy, except that P0 needs to be connected to an external pull-up resistor.
Software Description
Note: The software can use nested code blocks. It's not necessary to explain all parts of the software; only the important parts need to be explained. Code Block:
#include
void main()
{ unsigned char high, low; init_ds18b20(); // Initialize DS18B20 write_byte(0xcc); // Skip ROM operations write_byte(0x44); // Start temperature conversion delay(1000); // Wait for conversion to complete init_ds18b20(); // Initialize DS18B20 write_byte(0xcc); // Skip ROM operations write_byte(0xbe); // Read temperature register low = read_byte(); // Read low byte of temperature high = read_byte(); // Read high byte of temperature // Calculate temperature value printf("Temperature: %d.%d Celsius
", high, low); while(1);
printf(""/n);
}
void delay(unsigned int t) // Delay function { while(t--);}



void init_ds18b20() // Initialize DS18B20 { DQ = 1; // Pull the line high delay(8); // Delay 480us DQ = 0; // Send reset pulse delay(80); // Delay 4800us DQ = 1; // Release the bus delay(8); // Delay 480us }



unsigned char read_byte() // Read a byte { unsigned char i, dat = 0; for(i = 0; i { dat >>= 1; // Read data from high to low bits DQ = 0; // Send read command _nop_(); _nop_(); DQ = 1; // Release the bus _nop_(); _nop_(); if(DQ) // Read data dat |= 0x80; delay(8); // Delay } return dat;}



void write_byte(unsigned char dat) // Write a byte { unsigned char i; for(i = 0; i { DQ = 0; // Send write command DQ = dat & 0x01; _nop_(); _nop_(); DQ = 1; // Release bus dat >>= 1; // Next bit } delay(8); // Delay }





Physical demonstration
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