/*
* Copyright (c) 2015, Copyright Per Lindgren <per.o.lindgren@gmail.com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* This file is part of the Contiki operating system.
*
*
* Author : Per Lindgren <per.o.lindgren@gmail.com>
* Hacked by: Robert Olsson robert@radio-sensors.com
* Created : 2015-11-22
*/
#include "contiki.h"
#include "dev/temp-sensor.h"
#include <util/delay_basic.h>
#define delay_us(us) (_delay_loop_2(1 + (us * F_CPU) / 4000000UL))
const struct sensors_sensor temp_mcu_sensor;
/* probe_for_ds18b20 probes for the sensor. Returns 0 on failure, 1 on success
* Assumptions: only one sensor on the "1-wire bus", on port WSN_DS18B20_PORT
* BUG: THIS CODE DOES NOT WORK AS INTENDED! IT RETURNS "1" EVEN WHEN THERE
* IS NO SENSOR CONNECTED.
*/
uint8_t
ds18b20_probe(void)
{
uint8_t result = 0;
/* Reset 1W-bus */
/* Pull PIN low for 480 microseconds (us)
* Start with setting bit DS18B20_1_PIN to 0 */
OW_SET_PIN_LOW();
/* then set direction to OUT by setting DS18B20_1_DDR bit to 1 */
OW_SET_OUTPUT();
/* Delay 480 us */
clock_delay_usec(480);
/* See if sensor responds. First release the bus and switch to INput mode
* by setting DS18B20_1_DDR bit to 0 */
OW_SET_INPUT();
/* Activate internal pull-up by setting pin to HIGH (when in INput mode)
* OW_SET_PIN_HIGH();
* Wait for the pin to go HIGH for 64 us */
clock_delay_usec(64);
/* Now the sensor, if present, pulls the pin LOW for 60-240 us
* Detect 0 on PIND bit DS18B20_1_PIN. Invert the result so a presence
* (aka * a 0) sets "result" to 1 (for success) */
result = !OW_GET_PIN_STATE();
/* The sensor releases the pin so it goes HIGH after 240 us, add some
for the signal to stabilize, say 300 usecs to be on the safe side? */
if(result) {
clock_delay_usec(300);
/* Now the bus should be HIGH again */
result = OW_GET_PIN_STATE();
}
return result;
}
/* Write 1 or 0 on the bus */
void
write_bit(uint8_t bit)
{
/* Set pin to 0 */
OW_SET_OUTPUT();
OW_SET_PIN_LOW();
/* Pin should be 0 for at least 1 us */
clock_delay_usec(2);
/* If we're writing a 1, let interna pull-up pull the bus high
* within 15 us of setting the bus to low */
if(bit) {
/* Internal pull-up is activated by setting direction to IN and the
* setting the pin to HIGH */
OW_SET_INPUT();
OW_SET_PIN_HIGH();
}
/* OK, now the bus is either LOW, or pulled HIGH by the internal pull-up
* Let this state remain for 60 us, then release the bus */
clock_delay_usec(60);
/* Release the bus */
OW_SET_PIN_HIGH();
OW_SET_INPUT();
/* Allow > 1 us between read/write operations */
clock_delay_usec(2);
}
/* Read one bit of information from the bus, and return it as 1 or 0 */
uint8_t
read_bit(void)
{
uint8_t bit = 0;
/* Set pin to 0 */
OW_SET_OUTPUT();
OW_SET_PIN_LOW();
/* Pin should be 0 for at least 1 us */
clock_delay_usec(2);
/* Now read the bus, start by setting in/out direction and activating
* internal pull-up resistor */
OW_SET_INPUT();
OW_SET_PIN_HIGH();
/* ds18b20 either keeps the pin down or releases the bus and the
* bus then goes high because of the interna pull-up resistor
* Check whichever happens before 15 us has passed */
clock_delay_usec(15 - 2 - 1);
bit = OW_GET_PIN_STATE();
/* The complete read cycle must last at least 60 us. We have now spent
* about 14-15 us in delays, so add another delay to reach >= 60 us */
clock_delay_usec(50);
/* Release bus */
OW_SET_PIN_HIGH();
OW_SET_INPUT();
/* Allow > 1 us between read/write operations */
clock_delay_usec(2);
return bit ? 1 : 0;
}
/* Read one byte of information. A byte is read least significant bit first */
uint8_t
read_byte(void)
{
uint8_t result = 0;
uint8_t bit;
int i;
for(i = 0; i < 8; i++) {
bit = read_bit();
result += (bit << i);
}
return result;
}
/* Write one byte of information. A byte is written least significant bit first */
void
write_byte(uint8_t byte)
{
int i;
for(i = 0; i < 8; i++) {
write_bit((byte >> i) & 1);
}
}
/* ds18b20_get_temp returns the temperature in "temp" (in degrees celsius)
* Returns 0 on failure (and then "temp" is left unchanged
* Returns 1 on success, and sets temp */
uint8_t
ds18b20_get_temp(double *temp)
{
uint8_t result = 0;
/* Reset bus by probing. Probe returns 1 on success/presence of sensor */
if(ds18b20_probe()) {
/* write command "skip rom" since we only have one sensor on the wire! */
write_byte(DS18B20_COMMAND_SKIP_ROM);
/* write command to start measurement */
write_byte(DS18B20_COMMAND_START_CONVERSION);
/* Wait for conversion to complete. Conversion is 12-bit by default.
* Since we have external power to the sensor (ie not in "parasitic power"
* mode) the bus is held LOW by the sensor while the conversion is going
* on, and then HIGH when conversion is finished. */
OW_SET_INPUT();
int count = 0;
while(!OW_GET_PIN_STATE()) {
clock_delay_msec(10);
count++;
/* Longest conversion time is 750 ms (12-bit resolution)
* So if count > 80 (for a little margin!), we return -274.0
* which indicates failure to read the temperature. */
if(count > 80) {
return 0;
}
}
/* The result is stored in the "scratch pad", a 9 byte memory block.
* The first two bytes are the conversion result. Reading the scratch pad
* can be terminated by sending a reset signal (but we read all 9 bytes) */
(void)ds18b20_probe();
write_byte(DS18B20_COMMAND_SKIP_ROM);
write_byte(DS18B20_COMMAND_READ_SCRATCH_PAD);
uint8_t i, sp_arr[9];
for(i = 0; i < 9; i++) {
sp_arr[i] = read_byte();
}
/* Check CRC, if mismatch, return 0 (failure to read temperature) */
uint8_t crc_cal = crc8_ds18b20(sp_arr, 8);
if(crc_cal != sp_arr[8]) {
return 0;
}
/* OK, now decode what the temperature reading is. This code assumes
* 12-bit resolution, so this must be modified if the code is modified
* to use any other resolution! */
int16_t temp_res;
uint8_t temp_lsb = sp_arr[0];
uint8_t temp_msb = sp_arr[1];
temp_res = (int16_t)temp_msb << 8 | temp_lsb;
*temp = (double)temp_res * 0.0625;
result = 1;
}
return result;
}
/* crc8 algorithm for ds18b20 */
/* http://www.miscel.dk/MiscEl/CRCcalculations.html */
uint8_t
crc8_ds18b20(uint8_t *buf, uint8_t buf_len)
{
uint8_t result = 0;
uint8_t i, b;
for(i = 0; i < buf_len; i++) {
result = result ^ buf[i];
for(b = 1; b < 9; b++) {
if(result & 0x1) {
result = (result >> 1) ^ 0x8C;
} else {
result = result >> 1;
}
}
}
return result;
}
static int
value(int type)
{
double t;
int ret;
ret = ds18b20_get_temp(&t);
/* Return temp multiplied by 100 for two decimals */
if(ret)
return (int) (t * 100);
/* Error return largest negative value */
return 0x8000;
}
static int
configure(int type, int c)
{
ds18b20_probe();
return 0;
}
static int
status(int type)
{
return 1;
}
SENSORS_SENSOR(temp_sensor, TEMP_SENSOR, value, configure, status);