/* Project Swift - High altitude balloon flight software */

/*=======================================================================*/

/* Copyright 2010-2012 Philip Heron <phil@sanslogic.co.uk> */

/* Nigel Smart <nigel@projectswift.co.uk> */

/* */

/* This program is free software: you can redistribute it and/or modify */

/* it under the terms of the GNU General Public License as published by */

/* the Free Software Foundation, either version 3 of the License, or */

/* (at your option) any later version. */

/* */

/* This program is distributed in the hope that it will be useful, */

/* but WITHOUT ANY WARRANTY; without even the implied warranty of */

/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the */

/* GNU General Public License for more details. */

/* */

/* You should have received a copy of the GNU General Public License */

/* along with this program. If not, see <http://www.gnu.org/licenses/>. */

#include "config.h"

#include <stdint.h>

#include <stdlib.h>

#include <avr/io.h>

#include <util/delay.h>

#include <util/crc16.h>

#include "ds18x20.h"

/* The port and pin to use for 1-wire */

#define PIN _BV(3)

#define OUT DDRA

#define IN PINA

#define PORT PORTA

/* Helpers for 1-wire communications */

#define PIN_LOW() (PORT &= ~PIN)

#define PIN_HIGH() (PORT |= PIN)

#define PIN_IN() (OUT &= ~PIN)

#define PIN_OUT() (OUT |= PIN)

#define READ_PIN() (IN & PIN)

/* Delay times */

#define RESET_PULSE (480)

#define RESET_WAIT_LOW (80)

#define BEGIN_TIMESLOT (5)

#define DELAY_TIMESLOT (5)

#define TIMESLOT (60)

#define RECOVERY (10)

/* DS18x20 sensor IDs */

#define DS18S20_ID (0x10)

#define DS1822_ID (0x22)

#define DS18B20_ID (0x28)

static int ds_reset()

{

/* Reset pulse - pull line low for at least 480us */

PIN_LOW();

PIN_OUT();

_delay_us(RESET_PULSE);

PIN_IN();

/* The sensor should respond by pulling the line low

* after 15us to 60us for 60us to 240us. Wait for

* 80us for the line to go low */

_delay_us(RESET_WAIT_LOW);

if(READ_PIN()) return(DS_TIMEOUT);

_delay_us(RESET_PULSE - RESET_WAIT_LOW);

if(!READ_PIN()) return(DS_TIMEOUT);

return(DS_OK);

}

static void ds_write_bit(uint8_t b)

{

/* Begin a read/write time slot

* pull line low for between 1us and 15us */

PIN_LOW();

PIN_OUT();

_delay_us(BEGIN_TIMESLOT);

/* "1" is written by releasing the line immediatly */

if(b) PIN_IN();

/* Wait for the write slot to end and then release the line */

_delay_us(TIMESLOT - BEGIN_TIMESLOT);

PIN_IN();

_delay_us(RECOVERY);

}

static uint8_t ds_read_bit()

{

uint8_t i, b = 1;

/* Begin a read/write time slot

* pull line low for between 1us and 15us */

PIN_LOW();

PIN_OUT();

_delay_us(BEGIN_TIMESLOT);

PIN_IN();

_delay_us(DELAY_TIMESLOT);

/* If the sensor pulls the line low within

* the time slot the bit is 0 */

for(i = 0; i < TIMESLOT - BEGIN_TIMESLOT; i++)

{

if(!READ_PIN()) b = 0;

_delay_us(1);

}

_delay_us(RECOVERY);

return(b);

}

static void ds_write_byte(uint8_t b)

{

uint8_t i;

for(i = 0; i < 8; i++)

{

ds_write_bit(b & 1);

b >>= 1;

}

}

static uint8_t ds_read_byte()

{

uint8_t i, b = 0;

for(i = 0; i < 8; i++)

{

b >>= 1;

if(ds_read_bit()) b |= 1 << 7;

}

return(b);

}

int ds_search_rom(uint8_t *id, uint8_t mask)

{

uint8_t r, i, j;

uint8_t crc, b1, b2;

/* Reset the sensor(s) */

r = ds_reset();

if(r != DS_OK) return(r);

/* Transmit the SEARCH ROM command */

ds_write_byte(0xF0);

/* An ID is made up of 8 bytes (7 + CRC) */

for(crc = i = 0; i < 8; i++)

{

*id = 0;

for(j = 0; j < 8; j++)

{

/* Read the bit and its complement */

b1 = ds_read_bit();

b2 = ds_read_bit();

/* Both bits should never be 1 */

if(b1 && b2) return(DS_ERROR);

/* Both bits are 0 when two or more sensors

* respond with a different value */

if(b1 == b2)

{

b1 = mask & 1;

mask >>= 1;

/* Test if this is the last ID on the bus */

if(!b1) r = DS_MORE;

}

/* Let the sensors know which direction we're going */

ds_write_bit(b1);

*id >>= 1;

if(b1) *id |= 1 << 7;

}

/* Update the CRC, compare with last byte */

if(i != 7) crc = _crc_ibutton_update(crc, *id);

else if(crc != *id) return(DS_BADCRC);

id++;

}

return(r);

}

static int ds_match_rom(uint8_t *id)

{

uint8_t i;

/* Reset the sensor(s) */

i = ds_reset();

if(i != DS_OK) return(i);

/* Transmit the MATCH ROM command */

ds_write_byte(0x55);

/* Transmit the ID */

for(i = 0; i < 8; i++)

ds_write_byte(id[i]);

return(DS_OK);

}

static int ds_convert()

{

uint8_t i;

/* Send the command to begin a single temperature conversion */

ds_write_byte(0x44);

/* Wait until the sensor has finished conversion */

for(i = 0; ds_read_bit() && i < 100; i++) _delay_ms(1);

if(i == 100) return(DS_TIMEOUT);

return(DS_OK);

}

static int ds_read_scratchpad(uint8_t *sp)

{

uint8_t i, crc;

/* Send the command to read the scratchpad */

ds_write_byte(0xBE);

/* Read the 8 bytes of the scratchpad */

for(crc = i = 0; i < 8; i++)

crc = _crc_ibutton_update(crc, *(sp++) = ds_read_byte());

/* Read and check the CRC */

if(crc != (*sp = ds_read_byte())) return(DS_BADCRC);

return(DS_OK);

}

int ds_read_temperature(int32_t *temperature, uint8_t *id)

{

uint8_t sp[9], i;

int16_t temp;

/* Select the sensor */

i = ds_match_rom(id);

if(i != DS_OK) return(i);

/* Issue the convert command and wait for completion */

i = ds_convert(id);

if(i != DS_OK) return(i);

/* Re-select the sensor */

i = ds_match_rom(id);

if(i != DS_OK) return(i);

/* Read the scratchpad data */

i = ds_read_scratchpad(sp);

if(i != DS_OK) return(i);

switch(id[0])

{

case DS18B20_ID:

/* Read the result from the scratchpad */

temp = sp[0] | (sp[1] << 8);

/* Convert to a 4dp fixed-point integer */

*temperature = temp * 625L;

break;

case DS18S20_ID:

/* Read the result from the scratchpad */

temp = sp[0] | (sp[1] << 8);

/* Convert to a 4dp fixed-point integer */

*temperature = temp * 5000L;

break;

case DS1822_ID:

*temperature = 0;

break;

}

return(DS_OK);

}