Learning about Arduino and Maxim Temperature Sensor (DS1820 / DS18x20 / DS18S20)
Project Log
( 9 April 2009 )
- Modified temperature conversion code (may not be correct but gave semi-sane range of temperatures):
//Tc_100 = (6 * TReading) + TReading / 4; // multiply by (100 * 0.0625) or 6.25 Tc_100 = (50 * TReading);
- Wired Gnd <--> Gnd / DQ <--> Pin 10 & DQ <--> 4.7K <--> 5V / Vdd (No connection) (see here for more)
- Full code:
#include <OneWire.h> /* DS18S20 Temperature chip i/o */ OneWire ds(10); // on pin 10 void setup(void) { // initialize inputs/outputs // start serial port Serial.begin(9600); } int HighByte, LowByte, TReading, SignBit, Tc_100, Whole, Fract; void loop(void) { byte i; byte present = 0; byte data[12]; byte addr[8]; if ( !ds.search(addr)) { Serial.print("No more addresses.\n"); ds.reset_search(); return; } Serial.print("R="); for( i = 0; i < 8; i++) { Serial.print(addr[i], HEX); Serial.print(" "); } if ( OneWire::crc8( addr, 7) != addr[7]) { Serial.print("CRC is not valid!\n"); return; } if ( addr[0] != 0x10) { Serial.print("Device is not a DS18S20 family device.\n"); return; } ds.reset(); ds.select(addr); ds.write(0x44,1); // start conversion, with parasite power on at the end delay(1000); // maybe 750ms is enough, maybe not // we might do a ds.depower() here, but the reset will take care of it. present = ds.reset(); ds.select(addr); ds.write(0xBE); // Read Scratchpad Serial.print("P="); Serial.print(present,HEX); Serial.print(" "); for ( i = 0; i < 9; i++) { // we need 9 bytes data[i] = ds.read(); Serial.print(data[i], HEX); Serial.print(" "); } Serial.print(" CRC="); Serial.print( OneWire::crc8( data, 8), HEX); Serial.println(); LowByte = data[0]; HighByte = data[1]; TReading = (HighByte << 8) + LowByte; SignBit = TReading & 0x8000; // test most sig bit if (SignBit) // negative { TReading = (TReading ^ 0xffff) + 1; // 2's comp } //Tc_100 = (6 * TReading) + TReading / 4; // multiply by (100 * 0.0625) or 6.25 Tc_100 = (50 * TReading); Whole = Tc_100 / 100; // separate off the whole and fractional portions Fract = Tc_100 % 100; if (SignBit) // If its negative { Serial.print("-"); } Serial.print(Whole); Serial.print("."); if (Fract < 10) { Serial.print("0"); } Serial.print(Fract); Serial.print("\n"); }