DS12B20

ds12B20.c

#include <avr/io.h>
#include <avr/interrupt.h>
#define F_CPU 8000000UL
#include <util/delay.h>

#include <stdlib.h>

#include "ds18b20.h"

inline __attribute__((gnu_inline)) void therm_delay(uint16_t delay){
        while(delay--) asm volatile("nop");
}

uint8_t therm_reset() {
        uint8_t i;
        // Pull line low and wait for 480uS
        THERM_LOW();
        THERM_OUTPUT_MODE();
        //therm_delay(us(480));
        _delay_loop_2(960);

        //Release line and wait for 60uS
        THERM_INPUT_MODE();
        //therm_delay(us(60));
        _delay_loop_1(160);
        //Store line value and wait until the completion of 480uS period
        i=(THERM_PIN & (1<<THERM_DQ));
        //therm_delay(us(420));
        _delay_loop_2(840);
        //Return the value read from the presence pulse (0=OK, 1=WRONG)
        return i;
}

void therm_write_bit(uint8_t bit){
        //Pull line low for 1uS
        THERM_LOW();
        THERM_OUTPUT_MODE();
        //therm_delay(us(1));
        _delay_loop_1(3);
        //If we want to write 1, release the line (if not will keep low)
        if(bit) THERM_INPUT_MODE();
        //Wait for 60uS and release the line
        //therm_delay(us(60));
        _delay_loop_1(160);
        THERM_INPUT_MODE();
}

uint8_t therm_read_bit(void){
        uint8_t bit=0;
        //Pull line low for 1uS
        THERM_LOW();
        THERM_OUTPUT_MODE();
        //therm_delay(us(1));
        _delay_loop_1(3);

        //Release line and wait for 14uS
        THERM_INPUT_MODE();
        //therm_delay(us(14));
        _delay_loop_1(37);

        //Read line value
        if(THERM_PIN&(1<<THERM_DQ)) bit=1;
        //Wait for 45uS to end and return read value
        //therm_delay(us(45));
        _delay_loop_1(120);
        return bit;
}

uint8_t therm_read_byte(void){
        uint8_t i=8, n=0;
        while(i--){
                //Shift one position right and store read value
                n>>=1;
                n|=(therm_read_bit()<<7);
        }
        return n;
}

void therm_write_byte(uint8_t byte){
        uint8_t i=8;
        while(i--){
                //Write actual bit and shift one position right to make the next bit ready
                therm_write_bit(byte&1);
                byte>>=1;
        }
}


#define THERM_DECIMAL_STEPS_12BIT 625 //.0625
#define THERM_DECIMAL_STEPS_9BIT 500 //.500

void therm_read_temperature(int8_t *digit_part,  uint16_t *decimal_part){
        // Buffer length must be at least 12bytes long! ["+XXX.XXXX C"]
        uint8_t temperature[2];
        int8_t digit;
        uint16_t decimal;

        //Reset, skip ROM and start temperature conversion
        therm_reset();
        therm_write_byte(THERM_CMD_SKIPROM);
        therm_write_byte(THERM_CMD_CONVERTTEMP);
        //Wait until conversion is complete
        while(!therm_read_bit());
        //Reset, skip ROM and send command to read Scratchpad
        therm_reset();
        therm_write_byte(THERM_CMD_SKIPROM);
        therm_write_byte(THERM_CMD_RSCRATCHPAD);
        //Read Scratchpad (only 2 first bytes)
        temperature[0]=therm_read_byte();
        temperature[1]=therm_read_byte();
        therm_reset();

        //Store temperature integer digits and decimal digits
        digit=temperature[0]>>4;
        digit|=(temperature[1]&0x7)<<4;
        //Store decimal digits
        decimal=temperature[0]&0xf;
        decimal*=THERM_DECIMAL_STEPS_12BIT;

        *digit_part = digit;
        *decimal_part = decimal;

        //Format temperature into a string [+XXX.XXXX C]
        //sprintf(buffer, "%+d.%04u C", digit, decimal);

        //sprintf(buffer, "%d.%d\n",temperature[0]/2, (temperature[0]&1)*5 );
        //usart_write_str(buffer);
}

ds12B20.h

#ifndef DS18B20_H_
#define DS18B20_H_

#include <avr/io.h>
#include <avr/interrupt.h>

#ifndef F_CPU
#define F_CPU 8000000UL
#endif

#include <util/delay.h>
// LCD
#include <stdlib.h>
#include <avr/pgmspace.h>

#define LOOP_CYCLES     10      //Number of cycles that the loop takes
#define us(num)         (num/(LOOP_CYCLES*(1/(F_CPU/1000000.0))))

/* Thermometer Connections (At your choice) */
/*
#define THERM_PORT           PORTC
#define THERM_DDR            DDRC
#define THERM_PIN            PINC
#define THERM_DQ             PC0
*/
#define THERM_PORT           PORTE
#define THERM_DDR            DDRE
#define THERM_PIN            PINE
#define THERM_DQ             PE2

/* Utils */
#define THERM_INPUT_MODE()      THERM_DDR&=~(1<<THERM_DQ)
#define THERM_OUTPUT_MODE() THERM_DDR|=(1<<THERM_DQ)
#define THERM_LOW()                     THERM_PORT&=~(1<<THERM_DQ)
#define THERM_HIGH()            THERM_PORT|=(1<<THERM_DQ)

#define THERM_CMD_CONVERTTEMP   0x44
#define THERM_CMD_RSCRATCHPAD   0xbe
#define THERM_CMD_WSCRATCHPAD   0x4e
#define THERM_CMD_CPYSCRATCHPAD 0x48
#define THERM_CMD_RECEEPROM     0xb8
#define THERM_CMD_RPWRSUPPLY    0xb4
#define THERM_CMD_SEARCHROM     0xf0
#define THERM_CMD_READROM       0x33
#define THERM_CMD_MATCHROM      0x55
#define THERM_CMD_SKIPROM       0xcc
#define THERM_CMD_ALARMSEARCH   0xec

void therm_read_temperature(int8_t *digit_part,  uint16_t *decimal_part);
#endif /* */