ds18b20.c File Reference

#include "ds18b20.h"

Go to the source code of this file.

Functions
void	DS18B20_Init (void)
	Initialize DS18B20.
__BIT	DS18B20_Reset (void)
	Reset DS18B20.
__BIT	DS18B20_ReadBit (void)
	Read one bit from DS18B20.
uint8_t	DS18B20_ReadByte (void)
	Read one byte from DS18B20.
void	DS18B20_WriteBit (__BIT b)
	Write one bit to DS18B20.
void	DS18B20_WriteByte (uint8_t byte)
	Write one byte to DS18B20.
void	DS18B20_ReadScratchpad (uint8_t *buf)
	Read SRAM scratchpad.
uint8_t	DS18B20_Crc (uint8_t *addr, uint8_t len)
	8-bit CRC calculation
void	DS18B20_StartAll (void)
	Start conversion on all slaves.
__BIT	DS18B20_AllDone (void)
	If read bit is low, then device is not finished yet with calculation temperature.
void	DS18B20_ReadRom (uint8_t *buf)
	Read 64-bit ROM: 8-bit family code "0x28", unique 48-bit serial number, 8-bit CRC.
void	DS18B20_Select (const uint8_t *addr)
	Select a slave on the bus.
void	DS18B20_Start (const uint8_t *addr)
	Start conversion on selected slave.
void	DS18B20_ReadScratchpadFromAddr (const uint8_t *addr, uint8_t *buf)
	Read SRAM scratchpad from selected slave.
uint8_t	DS18B20_Search (uint8_t *buff, uint8_t *stack, uint8_t split_point)
	Perform one ROM search.

Function Documentation

DS18B20_AllDone()

__BIT DS18B20_AllDone

(

void

)

If read bit is low, then device is not finished yet with calculation temperature.

Returns

bit value

Definition at line 183 of file ds18b20.c.

{
    /* If read bit is low, then device is not finished yet with calculation temperature */
    return DS18B20_ReadBit();
}

DS18B20_Crc()

uint8_t DS18B20_Crc	(	uint8_t *	addr,
		uint8_t	len
	)

8-bit CRC calculation

Parameters

addr
len

Returns

crc result

Definition at line 151 of file ds18b20.c.

{
    uint8_t crc = 0, inbyte, i, mix;
 
    while (len--) 
    {
        inbyte = *addr++;
        for (i = 8; i; i--) 
        {
            mix = (crc ^ inbyte) & 0x01;
            crc >>= 1;
            if (mix) 
            {
                crc ^= 0x8C;
            }
            inbyte >>= 1;
        }
    }
    /* Return calculated CRC */
    return crc;
}

DS18B20_Init()

void DS18B20_Init

(

void

)

Initialize DS18B20.

Definition at line 17 of file ds18b20.c.

{
    /* Pull up 2 seconds for possible capacitor charging */
    DS18B20_DQ_PULLUP();
    DS18B20_DQ_OUTPUT();
    DS18B20_DQ = SET;
    SYS_Delay(1000);
    DS18B20_DQ = RESET;
    SYS_Delay(1);
    DS18B20_DQ = SET;
    SYS_Delay(1000);
}

DS18B20_ReadBit()

__BIT DS18B20_ReadBit

(

void

)

Read one bit from DS18B20.

Returns

bit value

Definition at line 49 of file ds18b20.c.

{
    __BIT b = RESET;
 
    /* Line low */
    DS18B20_DQ = RESET;
    DS18B20_DQ_OUTPUT();
    SYS_DelayUs(2);
 
    /* Release line */
    DS18B20_DQ_INPUT();
    SYS_DelayUs(10);
 
    /* Read line value */
    if (DS18B20_DQ) {
        /* Bit is HIGH */
        b = SET;
    }
 
    /* Wait 50us to complete 60us period */
    SYS_DelayUs(50);
    
    /* Return bit value */
    return b;
}

DS18B20_ReadByte()

uint8_t DS18B20_ReadByte

(

void

)

Read one byte from DS18B20.

Returns

byte value

Definition at line 75 of file ds18b20.c.

{
    uint8_t i = 8, byte = 0;
    while (i--) 
    {
        byte >>= 1;
        if (DS18B20_ReadBit())
        {
            byte |= 0x80;
        }
    }
    return byte;
}

DS18B20_ReadRom()

void DS18B20_ReadRom

(

uint8_t *

buf

)

Read 64-bit ROM: 8-bit family code "0x28", unique 48-bit serial number, 8-bit CRC.

Note

This command can only be used if there is a single DS18B20 on the bus. If multiple slaves are present, a data collision will occur(a wired AND result).

Parameters

buf	a 8-byte buffer

Definition at line 189 of file ds18b20.c.

{
    uint8_t i = 0;
    /* Reset pulse */
    DS18B20_Reset();
    /* Read rom */
    DS18B20_WriteByte(ONEWIRE_CMD_READROM);
    /* Get data */
    for (i = 0; i < 8; i++) 
    {
        /* Read byte by byte */
        *buf++ = DS18B20_ReadByte();
    }
}

DS18B20_ReadScratchpad()

void DS18B20_ReadScratchpad

(

uint8_t *

buf

)

Read SRAM scratchpad.

Parameters

buf	a 9-byte buffer, Byte 8 contains the CRC code for bytes 0 through 7

Definition at line 133 of file ds18b20.c.

{
    uint8_t i = 0;
    /* Reset line */
    DS18B20_Reset();
    /* Skip ROM */
    DS18B20_WriteByte(ONEWIRE_CMD_SKIPROM);
    /* Read scratchpad command by onewire protocol */
    DS18B20_WriteByte(ONEWIRE_CMD_RSCRATCHPAD);
 
    /* Get data */
    for (i = 0; i < 9; i++) 
    {
        /* Read byte by byte */
        *buf++ = DS18B20_ReadByte();
    }
}

DS18B20_ReadScratchpadFromAddr()

void DS18B20_ReadScratchpadFromAddr	(	const uint8_t *	addr,
		uint8_t *	buf
	)

Read SRAM scratchpad from selected slave.

Parameters

addr	64-bit ROM code
buf	a 9-byte buffer, Byte 8 contains the CRC code for bytes 0 through 7

Definition at line 224 of file ds18b20.c.

{
    uint8_t i = 0;
    /* Reset line */
    DS18B20_Reset();
    /* Select ROM number */
    DS18B20_Select(addr);
    /* Read scratchpad command by onewire protocol */
    DS18B20_WriteByte(ONEWIRE_CMD_RSCRATCHPAD);
 
    /* Get data */
    for (i = 0; i < 9; i++) 
    {
        /* Read byte by byte */
        *buf++ = DS18B20_ReadByte();
    }
}

DS18B20_Reset()

__BIT DS18B20_Reset

(

void

)

Reset DS18B20.

Returns

bit value

Definition at line 30 of file ds18b20.c.

{
    __BIT b;
 
    /* Line low, and wait 480us */
    DS18B20_DQ = RESET;
    DS18B20_DQ_OUTPUT();
    SYS_DelayUs(500);
    /* Release line and wait for 70us */
    DS18B20_DQ_INPUT();
    SYS_DelayUs(70);
    /* Check bit value, success if low */
    b = DS18B20_DQ;
    /* Delay for 410 us */
    SYS_DelayUs(410);
    /* Return value of presence pulse, 0 = OK, 1 = ERROR */
    return b;
}

DS18B20_Search()

uint8_t DS18B20_Search	(	uint8_t *	buff,
		uint8_t *	stack,
		uint8_t	split_point
	)

Perform one ROM search.

Parameters

buff	8-byte array for ROM bytes
stack	8-byte array for search stack
split_point	deepest split point of last search

Returns

new split point

Definition at line 242 of file ds18b20.c.

{
    uint8_t len = 64, pos = 0;
    /* Start from deepest point */
    split_point = (split_point == 0x00)? 0xFF : split_point;
    /* Reset line */
    DS18B20_Reset();
    /* Start searching */
    DS18B20_WriteByte(ONEWIRE_CMD_SEARCHROM);
 
    while (len--)
    {
        // Read the value and its complement value of this bit
        __BIT pb = DS18B20_ReadBit();
        __BIT cb = DS18B20_ReadBit();
        if (pb && cb) // no device
        {
            return 0;
        }
        else if (pb) // bit = 1
        {
            *(buff + pos / 8) |= 0x01 << (pos % 8);
            DS18B20_WriteBit(SET);
            // confirm: set this bit to 1
            *(stack + pos / 8) |= 0x01 << (pos % 8);
        }
        else if (cb) // bit = 0
        {
            *(buff + pos / 8) &= ~(0x01 << (pos % 8));
            DS18B20_WriteBit(RESET);
            // confirm: set this bit to 1
            *(stack + pos / 8) |= 0x01 << (pos % 8);
        }
        else // bit can be 0 or 1, possible split point
        {
            if (split_point == 0xFF || pos > split_point)
            {
                // new split point, try 0
                *(buff + pos / 8) &= ~(0x01 << (pos % 8));
                DS18B20_WriteBit(RESET);
                // unconfirm: set this bit to 0
                *(stack + pos / 8) &= ~(0x01 << (pos % 8));
                // record this new split point
                split_point = pos;
            }
            else if (pos == split_point)
            {
                // reach split point, try 1
                *(buff + pos / 8) |= 0x01 << (pos % 8);
                DS18B20_WriteBit(SET);
                // confirm: set this bit to 1
                *(stack + pos / 8) |= 0x01 << (pos % 8);
            }
            else // middle point, use existing bit
            {
                DS18B20_WriteBit(*(buff + pos / 8) >> (pos % 8) & 0x01);
            }
        }
        pos++;
    }
    // Relocate split point, move it to the last *unconfirmed* bit of stack
    while (split_point > 0 && *(stack + split_point / 8) >> (split_point % 8) & 0x01 == 0x01) split_point--;
    return split_point;
}

DS18B20_Select()

void DS18B20_Select

(

const uint8_t *

addr

)

Select a slave on the bus.

Note

Only the slave that exactly matches the 64-bit ROM code sequence will respond to the function command issued by the master; all other slaves on the bus will wait for a reset pulse.

Parameters

addr	64-bit ROM code

Definition at line 204 of file ds18b20.c.

{
    uint8_t len = 8;
    DS18B20_WriteByte(ONEWIRE_CMD_MATCHROM);
    while (len--)
    {
        DS18B20_WriteByte(*addr++);
    }
}

DS18B20_Start()

void DS18B20_Start

(

const uint8_t *

addr

)

Start conversion on selected slave.

Parameters

addr	64-bit ROM code

Definition at line 214 of file ds18b20.c.

{
    /* Reset pulse */
    DS18B20_Reset();
    /* Select ROM number */
    DS18B20_Select(addr);
    /* Start conversion on selected device */
    DS18B20_WriteByte(DS18B20_CMD_CONVERTTEMP);
}

DS18B20_StartAll()

void DS18B20_StartAll

(

void

)

Start conversion on all slaves.

Definition at line 173 of file ds18b20.c.

{
    /* Reset pulse */
    DS18B20_Reset();
    /* Skip rom */
    DS18B20_WriteByte(ONEWIRE_CMD_SKIPROM);
    /* Start conversion on all connected devices */
    DS18B20_WriteByte(DS18B20_CMD_CONVERTTEMP);
}

DS18B20_WriteBit()

void DS18B20_WriteBit

(

__BIT

b

)

Write one bit to DS18B20.

Parameters

b

bit value

Definition at line 89 of file ds18b20.c.

{
    if (b)
    {
        /* Set line low */
        DS18B20_DQ = RESET;
        DS18B20_DQ_OUTPUT();
        SYS_DelayUs(10);
 
        /* Bit high */
        DS18B20_DQ_INPUT();
        
        /* Wait for 55 us and release the line */
        SYS_DelayUs(55);
        DS18B20_DQ_INPUT();
    } 
    else 
    {
        /* Set line low */
        DS18B20_DQ = RESET;
        DS18B20_DQ_OUTPUT();
        SYS_DelayUs(65);
        
        /* Bit high */
        DS18B20_DQ_INPUT();
        
        /* Wait for 5 us and release the line */
        SYS_DelayUs(5);
        DS18B20_DQ_INPUT();
    }
}

DS18B20_WriteByte()

void DS18B20_WriteByte

(

uint8_t

byte

)

Write one byte to DS18B20.

Parameters

byte	byte value

Definition at line 121 of file ds18b20.c.

{
    uint8_t i = 8;
    /* Write 8 bits */
    while (i--) 
    {
        /* LSB bit is first */
        DS18B20_WriteBit(byte & 0x01);
        byte >>= 1;
    }
}