DS18B20 in Fahrenheit

Using an Arduino Nano + I2C LCD + DS18B20 temperature display example part 2:

Here is the temp converted from Celsius to Fahrenheit...

 iPhone photo - I2C LCD showing the DS18B20 in F

iPhone photo - I2C LCD showing the DS18B20 in F

The initial example was in Celsius but that makes life confusing when you live in an area where everything is measured in Fahrenheit. I wanted to see how complex the conversion between C & F was so I tweaked my code from the last example.

//Initial I2C LCD example from:
// http://arduino-info.wikispaces.com/LCD-Blue-I2C

// Initial DS18B20 example from:
// http://bildr.org/2011/07/ds18b20-arduino/

// Read the DS18B20 and then write to an I2C LCD and serial monitor
// http://www.hoaglun.com/blog/2013/1/31/ds18b20-in-fahrenheit

//The formula to convert Celsius to Fahrenheit
//Ftemp = (CTemp * 9.0)/ 5.0 + 32.0;


#include <Wire.h>
#include <OneWire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27,16,2); // set the LCD address to 0x27 for a 16 chars and 2 line display


int DS18S20_Pin = 2; //DS18S20 Signal pin on digital 2

//Temperature chip i/o
OneWire ds(DS18S20_Pin); // on digital pin 2

void setup(void) {
Serial.begin(9600);
lcd.init(); // initialize the lcd

// Print a message to the LCD.
lcd.backlight();
lcd.setCursor(0, 0);
lcd.print("Nano+I2C+DS18B20");
// lcd.setCursor(0, 1);
// lcd.print("Second Line");



}

void loop(void) {
float tempC = getTemp();
float tempF = (tempC * 9.0)/ 5.0 + 32.0;
Serial.println(tempF);
lcd.setCursor(0, 1);
lcd.print(tempF);
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;

}

To find the formula and implement it took about 10 minutes. It would probably be shorter if I actually worked with this platform often enough to retain the structure in my brain.  :-)

73 de NG0R