Temperature Sensor DS18B20 Arduino

Posted: February 10, 2013 by Rinanda Febriani in Bahasa C, Microcontroller

Pada posting yang lalu telah dibahas sebuah sensor suhu LM35DZ, yaitu sebuah sensor yang biasa digunakan untuk pengukuran suhu tubuh dalam termometer. DS18B20 merupakan sebuah sensor suhu dimana akurasi nilai suhu dan kecepatan pengukuran memiliki kestabilan yang jauh lebih baik dari sensor LM35DZ. DS18B20 adalah sensor suhu digital yang dikeluarkan oleh Dallas Semiconductor. Untuk pembacaan suhu, sensor menngunakan protokol 1 wire communication. DS18B20 memilki 3 pin yang terdiri dari +5V, Ground dan Data Input/Output.

Image

Berikut datasheet DS18B20  http://www.wvshare.com/datasheet/DALLAS_PDF/DS18B20.PDF

Temperature sensor DS18B20 beroperasi pada suhu -55 º celcius hingga +125 º celcius. Keunggulan DS18B20 yaitu output berupa data digital dengan nilai ketelitian 0.5 º celcius selama kisaran temperature 10 º celcius sampai + 85 º celcius  hingga mempermudah pembacaan oleh mikrokontroller. Dalam pemograman DS18B20, terdiri atas library OneWire.cpp dan OneWire.h.

Berikut program pengukur suhu tubuh pada DS18B20

#include "OneWire.h"
int DS18S20_Pin = 3; //DS18S20 Signal pin on digital 3

//Temperature chip i/o
OneWire ds(DS18S20_Pin); // on digital pin 3
void setup(void) {
 Serial.begin(9600);
}
void loop(void) {

 float temperature = getTemp();
 Serial.println(temperature);

 delay(100); //just here to slow down the output so it is easier to read

}

float getTemp(){
 //returns the temperature from one DS18S20 in DEG Celsius
byte data[12];
 byte addr[8];
if ( !ds.search(addr)) {
 //no more sensors on chain, reset search
 ds.reset_search();
 return -1000;
 }
if ( OneWire::crc8( addr, 7) != addr[7]) {
 Serial.println("CRC is not valid!");
 return -1000;
 }
if ( addr[0] != 0x10 && addr[0] != 0x28) {
 Serial.print("Device is not recognized");
 return -1000;
 }
ds.reset();
 ds.select(addr);
 ds.write(0x44,1); // start conversion, with parasite power on at the end
byte present = ds.reset();
 ds.select(addr); 
 ds.write(0xBE); // Read Scratchpad

 for (int i = 0; i < 9; i++) { // we need 9 bytes
 data[i] = ds.read();
 }

 ds.reset_search();

 byte MSB = data[1];
 byte LSB = data[0];
float tempRead = ((MSB << 8) | LSB); //using two's compliment
 float TemperatureSum = tempRead / 16;

 return TemperatureSum;

}

Dan berikut library yang digunakan pada program pengukuran DS18B20, karena Sensor ini menggunakan komunikasi 1 wire yaitu OneWire.cpp dan OneWire.h

/*
Copyright (c) 2007, Jim Studt
Updated to work with arduino-0008 and to include skip() as of
2007/07/06. --RJL20
Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:
The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
Much of the code was inspired by Derek Yerger's code, though I don't
think much of that remains. In any event that was..
 (copyleft) 2006 by Derek Yerger - Free to distribute freely.
The CRC code was excerpted and inspired by the Dallas Semiconductor 
sample code bearing this copyright.
//---------------------------------------------------------------------------
// Copyright (C) 2000 Dallas Semiconductor Corporation, All Rights Reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
// IN NO EVENT SHALL DALLAS SEMICONDUCTOR BE LIABLE FOR ANY CLAIM, DAMAGES
// OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
// OTHER DEALINGS IN THE SOFTWARE.
//
// Except as contained in this notice, the name of Dallas Semiconductor
// shall not be used except as stated in the Dallas Semiconductor
// Branding Policy.
//--------------------------------------------------------------------------
*/
#include "OneWire.h"
extern "C" {
#if (ARDUINO >= 100)
#include <Arduino.h>
#else
#include <WProgram.h>
#endif
#include <avr/io.h>
#include "pins_arduino.h"
}

OneWire::OneWire( uint8_t pinArg)
{
 pin = pinArg;
 port = digitalPinToPort(pin);
 bitmask = digitalPinToBitMask(pin);
 outputReg = portOutputRegister(port);
 inputReg = portInputRegister(port);
 modeReg = portModeRegister(port);
#if ONEWIRE_SEARCH
 reset_search();
#endif
}
//
// Perform the onewire reset function. We will wait up to 250uS for
// the bus to come high, if it doesn't then it is broken or shorted
// and we return a 0;
//
// Returns 1 if a device asserted a presence pulse, 0 otherwise.
//
uint8_t OneWire::reset() {
 uint8_t r;
 uint8_t retries = 125;
// wait until the wire is high... just in case
 pinMode(pin,INPUT);
 do {
 if ( retries-- == 0) return 0;
 delayMicroseconds(2); 
 } while( !digitalRead( pin));

 digitalWrite(pin,0); // pull low for 500uS
 pinMode(pin,OUTPUT);
 delayMicroseconds(500);
 pinMode(pin,INPUT);
 delayMicroseconds(65);
 r = !digitalRead(pin);
 delayMicroseconds(490);
 return r;
}
//
// Write a bit. Port and bit is used to cut lookup time and provide
// more certain timing.
//
void OneWire::write_bit(uint8_t v) {
 static uint8_t lowTime[] = { 55, 5 };
 static uint8_t highTime[] = { 5, 55};

 v = (v&1);
 *modeReg |= bitmask; // make pin an output, do first since we
 // expect to be at 1
 *outputReg &= ~bitmask; // zero
 delayMicroseconds(lowTime[v]);
 *outputReg |= bitmask; // one, push pin up - important for
 // parasites, they might start in here
 delayMicroseconds(highTime[v]);
}
//
// Read a bit. Port and bit is used to cut lookup time and provide
// more certain timing.
//
uint8_t OneWire::read_bit() {
 uint8_t r;

 *modeReg |= bitmask; // make pin an output, do first since we expect to be at 1
 *outputReg &= ~bitmask; // zero
 delayMicroseconds(1);
 *modeReg &= ~bitmask; // let pin float, pull up will raise
 delayMicroseconds(5); // A "read slot" is when 1mcs > t > 2mcs
 r = ( *inputReg & bitmask) ? 1 : 0; // check the bit
 delayMicroseconds(50); // whole bit slot is 60-120uS, need to give some time

 return r;
}
//
// Write a byte. The writing code uses the active drivers to raise the
// pin high, if you need power after the write (e.g. DS18S20 in
// parasite power mode) then set 'power' to 1, otherwise the pin will
// go tri-state at the end of the write to avoid heating in a short or
// other mishap.
//
void OneWire::write(uint8_t v, uint8_t power) {
 uint8_t bitMask;

 for (bitMask = 0x01; bitMask; bitMask <<= 1) {
 OneWire::write_bit( (bitMask & v)?1:0);
 }
 if ( !power) {
 pinMode(pin,INPUT);
 digitalWrite(pin,0);
 }
}
//
// Read a byte
//
uint8_t OneWire::read() {
 uint8_t bitMask;
 uint8_t r = 0;

 for (bitMask = 0x01; bitMask; bitMask <<= 1) {
 if ( OneWire::read_bit()) r |= bitMask;
 }
 return r;
}
//
// Do a ROM select
//
void OneWire::select( uint8_t rom[8])
{
 int i;
write(0x55,0); // Choose ROM
for( i = 0; i < 8; i++) write(rom[i],0);
}
//
// Do a ROM skip
//
void OneWire::skip()
{
 write(0xCC,0); // Skip ROM
}
void OneWire::depower()
{
 pinMode(pin,INPUT);
}
#if ONEWIRE_SEARCH
//
// You need to use this function to start a search again from the beginning.
// You do not need to do it for the first search, though you could.
//
void OneWire::reset_search()
{
 uint8_t i;

 searchJunction = -1;
 searchExhausted = 0;
 for( i = 7; ; i--) {
 address[i] = 0;
 if ( i == 0) break;
 }
}
//
// Perform a search. If this function returns a '1' then it has
// enumerated the next device and you may retrieve the ROM from the
// OneWire::address variable. If there are no devices, no further
// devices, or something horrible happens in the middle of the
// enumeration then a 0 is returned. If a new device is found then
// its address is copied to newAddr. Use OneWire::reset_search() to
// start over.
// 
uint8_t OneWire::search(uint8_t *newAddr)
{
 uint8_t i;
 char lastJunction = -1;
 uint8_t done = 1;

 if ( searchExhausted) return 0;

 if ( !reset()) return 0;
 write( 0xf0, 0);

 for( i = 0; i < 64; i++) {
 uint8_t a = read_bit( );
 uint8_t nota = read_bit( );
 uint8_t ibyte = i/8;
 uint8_t ibit = 1<<(i&7);

 if ( a && nota) return 0; // I don't think this should happen, this means nothing responded, but maybe if
 // something vanishes during the search it will come up.
 if ( !a && !nota) {
 if ( i == searchJunction) { // this is our time to decide differently, we went zero last time, go one.
 a = 1;
 searchJunction = lastJunction;
 } else if ( i < searchJunction) { // take whatever we took last time, look in address
 if ( address[ ibyte]&ibit) a = 1;
 else { // Only 0s count as pending junctions, we've already exhasuted the 0 side of 1s
 a = 0;
 done = 0;
 lastJunction = i;
 }
 } else { // we are blazing new tree, take the 0
 a = 0;
 searchJunction = i;
 done = 0;
 }
 lastJunction = i;
 }
 if ( a) address[ ibyte] |= ibit;
 else address[ ibyte] &= ~ibit;

 write_bit( a);
 }
 if ( done) searchExhausted = 1;
 for ( i = 0; i < 8; i++) newAddr[i] = address[i];
 return 1; 
}
#endif
// This table comes from Dallas sample code where it is freely reusable, though Copyright (C) 2000 Dallas Semiconductor Corporation
static uint8_t dscrc_table[] = {
 0, 94,188,226, 97, 63,221,131,194,156,126, 32,163,253, 31, 65,
 157,195, 33,127,252,162, 64, 30, 95, 1,227,189, 62, 96,130,220,
 35,125,159,193, 66, 28,254,160,225,191, 93, 3,128,222, 60, 98,
 190,224, 2, 92,223,129, 99, 61,124, 34,192,158, 29, 67,161,255,
 70, 24,250,164, 39,121,155,197,132,218, 56,102,229,187, 89, 7,
 219,133,103, 57,186,228, 6, 88, 25, 71,165,251,120, 38,196,154,
 101, 59,217,135, 4, 90,184,230,167,249, 27, 69,198,152,122, 36,
 248,166, 68, 26,153,199, 37,123, 58,100,134,216, 91, 5,231,185,
 140,210, 48,110,237,179, 81, 15, 78, 16,242,172, 47,113,147,205,
 17, 79,173,243,112, 46,204,146,211,141,111, 49,178,236, 14, 80,
 175,241, 19, 77,206,144,114, 44,109, 51,209,143, 12, 82,176,238,
 50,108,142,208, 83, 13,239,177,240,174, 76, 18,145,207, 45,115,
 202,148,118, 40,171,245, 23, 73, 8, 86,180,234,105, 55,213,139,
 87, 9,235,181, 54,104,138,212,149,203, 41,119,244,170, 72, 22,
 233,183, 85, 11,136,214, 52,106, 43,117,151,201, 74, 20,246,168,
 116, 42,200,150, 21, 75,169,247,182,232, 10, 84,215,137,107, 53};
//
// Compute a Dallas Semiconductor 8 bit CRC. These show up in the ROM
// and the registers. (note: this might better be done without to
// table, it would probably be smaller and certainly fast enough
// compared to all those delayMicrosecond() calls. But I got
// confused, so I use this table from the examples.) 
//
uint8_t OneWire::crc8( uint8_t *addr, uint8_t len)
{
 uint8_t i;
 uint8_t crc = 0;

 for ( i = 0; i < len; i++) {
 crc = dscrc_table[ crc ^ addr[i] ];
 }
 return crc;
}
#if ONEWIRE_CRC16
static short oddparity[16] = { 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0 };
//
// Compute a Dallas Semiconductor 16 bit CRC. I have never seen one of
// these, but here it is.
//
unsigned short OneWire::crc16(unsigned short *data, unsigned short len)
{
 unsigned short i;
 unsigned short crc = 0;

 for ( i = 0; i < len; i++) {
 unsigned short cdata = data[len];

 cdata = (cdata ^ (crc & 0xff)) & 0xff;
 crc >>= 8;

 if (oddparity[cdata & 0xf] ^ oddparity[cdata >> 4]) crc ^= 0xc001;

 cdata <<= 6;
 crc ^= cdata;
 cdata <<= 1;
 crc ^= cdata;
 }
 return crc;
}
#endif

Dan sebuah library OneWire.h

#ifndef OneWire_h
#define OneWire_h
#if (ARDUINO >= 100)
#include <Arduino.h>
#else
#include <WProgram.h>
#endif
#include <inttypes.h>
// you can exclude onewire_search by defining that to 0
#ifndef ONEWIRE_SEARCH
#define ONEWIRE_SEARCH 1
#endif
// You can exclude onewire_crc16 by defining that to 0
#ifndef ONEWIRE_CRC16
#define ONEWIRE_CRC16 0
#endif
class OneWire
{
 private:
#if ONEWIRE_SEARCH
 uint8_t address[8];
 char searchJunction;
 uint8_t searchExhausted;
#endif
 uint8_t pin;
 uint8_t port;
 uint8_t bitmask;
 volatile uint8_t *outputReg;
 volatile uint8_t *inputReg;
 volatile uint8_t *modeReg;
public:
 OneWire( uint8_t pin);

 // Perform a 1-Wire reset cycle. Returns 1 if a device responds
 // with a presence pulse. Returns 0 if there is no device or the
 // bus is shorted or otherwise held low for more than 250uS
 uint8_t reset();
// Issue a 1-Wire rom select command, you do the reset first.
 void select( uint8_t rom[8]);
// Issue a 1-Wire rom skip command, to address all on bus.
 void skip();
// Write a byte. If 'power' is one then the wire is held high at
 // the end for parasitically powered devices. You are responsible
 // for eventually depowering it by calling depower() or doing
 // another read or write.
 void write( uint8_t v, uint8_t power = 0);
// Read a byte.
 uint8_t read();
// Write a bit. The bus is always left powered at the end, see
 // note in write() about that.
 void write_bit( uint8_t v);
// Read a bit.
 uint8_t read_bit();
// Stop forcing power onto the bus. You only need to do this if
 // you used the 'power' flag to write() or used a write_bit() call
 // and aren't about to do another read or write. You would rather
 // not leave this powered if you don't have to, just in case
 // someone shorts your bus.
 void depower();
#if ONEWIRE_SEARCH
 // Clear the search state so that if will start from the beginning again.
 void reset_search();
// Look for the next device. Returns 1 if a new address has been
 // returned. A zero might mean that the bus is shorted, there are
 // no devices, or you have already retrieved all of them. It
 // might be a good idea to check the CRC to make sure you didn't
 // get garbage. The order is deterministic. You will always get
 // the same devices in the same order.
 uint8_t search(uint8_t *newAddr);
#endif
// Compute a Dallas Semiconductor 8 bit CRC, these are used in the
 // ROM and scratchpad registers.
 static uint8_t crc8( uint8_t *addr, uint8_t len);
#if ONEWIRE_CRC16
 // Compute a Dallas Semiconductor 16 bit CRC. Maybe. I don't have
 // any devices that use this so this might be wrong. I just copied
 // it from their sample code.
 static unsigned short crc16(unsigned short *data, unsigned short len);
#endif
};
#endif

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