== DS18S20/DS18B20 == The DS18S20 and DS18P20 are two temperature sensors from Dallas. They function on a one-wire bus which mean that for communication you need just a single wire. == Code to detect temperature sensors on a one-wire bus == The code for doing this : [code,c] ------ #include <OneWire.h> //init the one wire interface on pin 10 OneWire ow(10); void setup(void) { Serial.begin(9600); lookUpSensors(); } void lookUpSensors(){ byte address[8]; int i=0; byte ok = 0, tmp = 0; //start the search Serial.println("--Search started--"); while (ow.search(address)){ tmp = 0; //0x10 = DS18S20 if (address[0] == 0x10){ Serial.print("Device is a DS18S20 : "); tmp = 1; } else { //0x28 = DS18B20 if (address[0] == 0x28){ Serial.print("Device is a DS18B20 : "); tmp = 1; } } //display the address, if tmp is ok if (tmp == 1){ if (OneWire::crc8(address, 7) != address[7]){ Serial.println("but it doesn't have a valid CRC!"); } else { //all is ok, display it for (i=0;i<8;i++){ if (address[i] < 9){ Serial.print("0"); } Serial.print(address[i],HEX); if (i<7){ Serial.print("-"); } } Serial.println(""); ok = 1; } }//end if tmp }//end while if (ok == 0){ Serial.println("No devices were found"); } Serial.println("--Search ended--"); } void loop(void) { //do nothing :) } ------ and an output sample : [code,text] ------ --Search started-- Device is a DS18S20 : 10-1D-30-F9-01-08-00-51 --Search ended-- ------ == Read the temperature in Celsius and Fahrenheit degrees == The code for reading the temperature from the temperature sensors : [code,c] ------ #include <OneWire.h> //init the one wire interface on pin 10 OneWire ow(10); //write here the address you receive from the other program byte sensor[8] = {0x10, 0x1D, 0x30, 0xF9, 0x01, 0x08, 0x00, 0x51}; void setup(void) { Serial.begin(9600); } void writeTimeToScratchpad(byte* address){ //reset the bus ow.reset(); //select our sensor ow.select(address); //CONVERT T function call (44h) which puts the temperature into the scratchpad ow.write(0x44,1); //sleep a second for the write to take place delay(1000); } void readTimeFromScratchpad(byte* address, byte* data){ //reset the bus ow.reset(); //select our sensor ow.select(address); //read the scratchpad (BEh) ow.write(0xBE); for (byte i=0;i<9;i++){ data[i] = ow.read(); } } float getTemperature(byte* address){ int tr; byte data[12]; writeTimeToScratchpad(address); readTimeFromScratchpad(address,data); //put in temp all the 8 bits of LSB (least significant byte) tr = data[0]; //check for negative temperature if (data[1] > 0x80){ tr = !tr + 1; //two's complement adjustment tr = tr * -1; //flip value negative. } //COUNT PER Celsius degree (10h) int cpc = data[7]; //COUNT REMAIN (0Ch) int cr = data[6]; //drop bit 0 tr = tr >> 1; //calculate the temperature based on this formula : //TEMPERATURE = TEMP READ - 0.25 + (COUNT PER Celsius Degree - COUNT REMAIN) / (COUNT PER Celsius Degree) return tr - (float)0.25 + (cpc - cr)/(float)cpc; } //fahrenheit to celsius conversion float f2c(float val){ float aux = val - 32; return (aux * 5 / 9); } //celsius to fahrenheit conversion float c2f(float val){ float aux = (val * 9 / 5); return (aux + 32); } void loop(void) { float temp; float tmp2; tmp2 = getTemperature(sensor); temp = c2f(tmp2); Serial.print("Temp = "); Serial.print(temp); Serial.print(" F or "); Serial.print(tmp2); Serial.println(" C"); //wait 30 seconds delay(30000); } ------ == An image of the project == Here is an image of the project : image:http://stuff.nekhbet.ro/wp-content/uploads/2009/08/real-scheme-ds18s20.jpg[http://stuff.nekhbet.ro/wp-content/uploads/2009/08/real-scheme-ds18s20.jpg]

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