Source forum: here
I find that the codes available in this site for DS18S20 & DS18B20 is a bit messy and complicated.
Below is the simple version of the codes which works. It also take care of negative temperature.
However, due to its simplicity, this will only work with one DS1820 connected to the 1-wire bus of the PIC. This code will not work with 2 or more DS1820 sharing the same 1-wire bus.
1wire.c
| Code: |
// (C) copyright 2003 j.d.sandoz / jds-pic !at! losdos.dyndns.org // released under the GNU GENERAL PUBLIC LICENSE (GPL) // refer to http://www.gnu.org/licenses/gpl.txt // 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 2 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, write to the Free Software // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA /***********************1Wire Class***************/ /*Description: This class handles all communication */ /* between the processor and the 1wire */ /* sensors. /****************************************************/ /*-------1-wire definitions-------*/ #define ONE_WIRE_PIN PIN_A0 /********1-wire communication functions***********/ /*******onewire_reset*******************************/ /*This function initiates the 1wire bus */ /* */ /*PARAMETERS: */ /*RETURNS: */ /****************************************************/ void onewire_reset() // OK if just using a single permanently connected device { output_low(ONE_WIRE_PIN); delay_us( 500 ); // pull 1-wire low for reset pulse output_float(ONE_WIRE_PIN); // float 1-wire high delay_us( 500 ); // wait-out remaining initialisation window. output_float(ONE_WIRE_PIN); } /************** onewire_write() **********************/ /*This function writes a byte to the sensor.*/ /* */ /*Parameters: byte - the byte to be written to the 1-wire */ /*Returns: */ /*******************************************************/ void onewire_write(int data) { int count; for (count=0; count<8; ++count) { output_low(ONE_WIRE_PIN); delay_us( 2 ); // pull 1-wire low to initiate write time-slot. output_bit(ONE_WIRE_PIN, shift_right(&data,1,0)); // set output bit on 1-wire delay_us( 60 ); // wait until end of write slot. output_float(ONE_WIRE_PIN); // set 1-wire high again, delay_us( 2 ); // for more than 1us minimum. } } /**************** read1wire() ********************/ /*This function reads the 8 -bit data via the 1-wire sensor. */ /* */ /*Parameters: */ /*Returns: 8-bit (1-byte) data from sensor */ /**************************************************/ int onewire_read() { int count, data; for (count=0; count<8; ++count) { output_low(ONE_WIRE_PIN); delay_us( 2 ); // pull 1-wire low to initiate read time-slot. output_float(ONE_WIRE_PIN); // now let 1-wire float high, delay_us( 8 ); // let device state stabilise, shift_right(&data,1,input(ONE_WIRE_PIN)); // and load result. delay_us( 120 ); // wait until end of read slot. } return( data ); } |
ds1820.c
| Code: |
float ds1820_read() { int8 busy=0, temp1, temp2; signed int16 temp3; float result; onewire_reset(); onewire_write(0xCC); onewire_write(0x44); while (busy == 0) busy = onewire_read(); onewire_reset(); onewire_write(0xCC); onewire_write(0xBE); temp1 = onewire_read(); temp2 = onewire_read(); temp3 = make16(temp2, temp1); result = (float) temp3 / 2.0; //Calculation for DS18S20 with 0.5 deg C resolution // result = (float) temp3 / 16.0; //Calculation for DS18B20 with 0.1 deg C resolution delay_ms(200); return(result); } |
Main code
| Code: |
#include <16F877A.h> #device *=16 #device adc=8 #FUSES NOWDT, HS, PUT, NOPROTECT, NODEBUG, BROWNOUT, NOLVP, NOCPD, NOWRT #use delay(clock=20000000) #include<1wire.c> #include<lcd.c> #include<ds1820.c> void main() { float temperature; setup_adc_ports(NO_ANALOGS); setup_adc(ADC_OFF); setup_psp(PSP_DISABLED); setup_spi(FALSE); setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1); setup_timer_1(T1_DISABLED); setup_timer_2(T2_DISABLED,0,1); setup_comparator(NC_NC_NC_NC); setup_vref(VREF_LOW|-2); lcd_init(); lcd_putc("\f"); while (1) { temperature = ds1820_read(); lcd_gotoxy(1,1); printf(lcd_putc,"TEMP: %3.1f ", temperature); lcd_putc(223); lcd_putc("C "); lcd_gotoxy(1,2); if(temperature >= 29.0) printf(lcd_putc,"Hot! "); else if( temperature >= 20 && temperature < 29.0) printf(lcd_putc,"Comfort!"); else printf(lcd_putc,"Cold! "); } } |
Last edited by hansolo on Sun Oct 15, 2006 5:56 pm; edited 1 time in total