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MAX6875 Temp Sensor example
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‎libraries/MAX6675/MAX6675.cpp

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/*
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MAX6675.cpp - Library for reading temperature from a MAX6675.
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This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.
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http://creativecommons.org/licenses/by-sa/3.0/
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*/
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#include <MAX6675.h>
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MAX6675::MAX6675(uint8_t CS_pin, uint8_t SO_pin, uint8_t SCK_pin, uint8_t units)
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{
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pinMode(CS_pin, OUTPUT);
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pinMode(SO_pin, INPUT);
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pinMode(SCK_pin, OUTPUT);
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digitalWrite(CS_pin, HIGH);
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_CS_pin = CS_pin;
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_SO_pin = SO_pin;
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_SCK_pin = SCK_pin;
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_units = units;
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}
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float MAX6675::read_temp()
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{
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uint16_t value = 0;
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uint8_t error_tc = 0;
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float temp = 0.0;
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/*
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Initiate a temperature conversion. According to MAX's tech notes FAQ's
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for the chip, Line going high initiates a conversion, which means, we
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need to clock the chip low to high to initiate the conversion, then wait
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for the conversion to be complete before trying to read the data from
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the chip.
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*/
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digitalWrite(_CS_pin,LOW);
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delay(2);
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digitalWrite(_CS_pin,HIGH);
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delay(220);
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/* Read the chip and return the raw temperature value */
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/*
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Bring CS pin low to allow us to read the data from
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the conversion process
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*/
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digitalWrite(_CS_pin,LOW);
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/* Cycle the clock for dummy bit 15 */
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digitalWrite(_SCK_pin,HIGH);
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delay(1);
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digitalWrite(_SCK_pin,LOW);
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/*
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Read bits 14-3 from MAX6675 for the Temp. Loop for each bit reading
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the value and storing the final value in 'temp'
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*/
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for (int i=11; i>=0; i--) {
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digitalWrite(_SCK_pin,HIGH);
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value += digitalRead(_SO_pin) << i;
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digitalWrite(_SCK_pin,LOW);
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}
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/* Read the TC Input inp to check for TC Errors */
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digitalWrite(_SCK_pin,HIGH);
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error_tc = digitalRead(_SO_pin);
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digitalWrite(_SCK_pin,LOW);
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/*
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Read the last two bits from the chip, faliure to do so will result
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in erratic readings from the chip.
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*/
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for (int i=1; i>=0; i--) {
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digitalWrite(_SCK_pin,HIGH);
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delay(1);
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digitalWrite(_SCK_pin,LOW);
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}
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// Disable Device
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digitalWrite(_CS_pin, HIGH);
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/*
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Keep in mind that the temp that was just read is on the digital scale
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from 0˚C to 1023.75˚C at a resolution of 2^12. We now need to convert
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to an actual readable temperature (this drove me nuts until I figured
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this out!). Now multiply by 0.25. I tried to avoid float math but
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it is tough to do a good conversion to ˚F. THe final value is converted
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to an int and returned at x10 power.
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2 = temp in deg F
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1 = temp in deg C
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0 = raw chip value 0-4095
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*/
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if(_units == 2) {
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temp = (value*0.25) * 9.0/5.0 + 32.0;
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} else if(_units == 1) {
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temp = (value*0.25);
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} else {
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temp = value;
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}
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/* Output negative of CS_pin if there is a TC error, otherwise return 'temp' */
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if(error_tc != 0) {
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return -_CS_pin;
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} else {
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return temp;
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}
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}

‎libraries/MAX6675/MAX6675.h

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/*
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MAX6675.h - Library for reading temperature from a MAX6675.
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This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.
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http://creativecommons.org/licenses/by-sa/3.0/
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*/
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#ifndef MAX6675_h
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#define MAX6675_h
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#if defined(ARDUINO) && ARDUINO >= 100
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#include "Arduino.h"
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#else
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#include "WProgram.h"
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#endif
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class MAX6675
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{
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public:
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MAX6675(uint8_t CS_pin, uint8_t SO_pin, uint8_t SCK_pin, uint8_t units);
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float read_temp();
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private:
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uint8_t _CS_pin;
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uint8_t _SO_pin;
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uint8_t _SCK_pin;
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uint8_t _units;
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uint8_t chip_read(uint8_t CS_pin, uint8_t &error_tc);
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};
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#endif

‎libraries/MAX6675/README.markdown

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MAX6675 Arduino Library
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=======================
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Version: **2.0.1**
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This work is licensed under a <a rel="license" href="http://creativecommons.org/licenses/by-sa/3.0/">Creative Commons Attribution-ShareAlike 3.0 Unported License</a>.
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Summary
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-------
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The primary use of the library is to easily interface with a MAX6675 chip via it's SPI interface. Use the following code to initialize the library. V2 also greatly improves performance and timing of the chip for more accurate reads. Thanks Ed!
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MAX6675 temp0(CS,SO,SCK,units);
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Variables:
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* CS is chip select pin of chip
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* SO is data out of the chip
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* SCK is the clock pin of the chip
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* units is one of the following:
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* 0 = raw 0-4095 value
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* 1 = temp in ˚C
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* 2 = temp in ˚F
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Following this you can use the _read_temp()_ function to return the temperature as a float.
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temperature = temp0.read_temp();
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‎libraries/MAX6675/examples/read_temp/read_temp.pde

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/*
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Single_Temp.pde - Example using the MAX6675 Library.
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Created by Ryan McLaughlin <[email protected]>
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This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.
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http://creativecommons.org/licenses/by-sa/3.0/
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*/
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#include <MAX6675.h>
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int LED1 = 9; // Status LED Pin
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int CS = 10; // CS pin on MAX6675
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int SO = 12; // SO pin of MAX6675
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int SCK = 13; // SCK pin of MAX6675
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int units = 2; // Units to readout temp (0 = raw, 1 = ˚C, 2 = ˚F)
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float temperature = 0.0; // Temperature output variable
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// Initialize the MAX6675 Library for our chip
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MAX6675 temp(CS,SO,SCK,units);
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// Setup Serial output and LED Pin
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// MAX6675 Library already sets pin modes for MAX6675 chip!
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void setup() {
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Serial.begin(9600);
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pinMode(LED1, OUTPUT);
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}
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void loop() {
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// Read the temp from the MAX6675
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temperature = temp.read_temp();
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if(temperature < 0) {
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// If there is an error with the TC, temperature will be < 0
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Serial.print("Thermocouple Error on CS");
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Serial.println( temperature );
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digitalWrite(LED1, HIGH);
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} else {
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Serial.print("Current Temperature: ");
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Serial.println( temperature );
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digitalWrite(LED1, LOW);
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}
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// Wait one second before reading again
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delay(1000);
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}

‎libraries/MAX6675/keywords.txt

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#######################################
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# Syntax Coloring Map For MAX6675
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#######################################
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#######################################
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# Datatypes (KEYWORD1)
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#######################################
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MAX6675 KEYWORD1
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#######################################
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# Methods and Functions (KEYWORD2)
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#######################################
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read_temp KEYWORD2
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‎libraries/MySensors/examples/MAX6875TemperatureSensor/MAX6875TemperatureSensor.ino

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// MAX6875 Hight temperature sensor with range: -200 degC - +1300 degC
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// Contribution by MrLynx
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// http://forum.mysensors.org/topic/641/max6675
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//
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// Connect:
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// MAX6675 - Arduino
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// CS0 - 4
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// SO - 3
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// SCLK - 5
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// VCC - 5V
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// GND - GND
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#include <MySensor.h>
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#include <MAX6675.h>
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#include <SPI.h>
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uint8_t CS0 = 4; // CS pin on MAX6675
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uint8_t SO = 3; // SO pin of MAX6675
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uint8_t SCLK = 5; // SCK pin of MAX6675
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uint8_t units = 1; // Units to readout temp (0 = ˚F, 1 = ˚C)
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float temperature = 0.0; // Temperature output variable
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float lastTemperature;
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unsigned long SLEEP_TIME = 30000;
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boolean metric = true;
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MySensor gw;
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MyMessage msg(0, V_TEMP);
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// Initialize the MAX6675 Library for our chip
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MAX6675 temp0(CS0, SO, SCLK, units);
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void setup()
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{
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// Startup and initialize MySensors library. Set callback for incoming messages.
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gw.begin();
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// Send the sketch version information to the gateway and Controller
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gw.sendSketchInfo("Max6675 Temp Sensor", "1.0");
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// Present all sensors to controller
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gw.present(0, S_TEMP);
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}
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void loop()
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{
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// Process incoming messages (like config from server)
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gw.process();
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temperature = temp0.read_temp(); // Read the temp
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if (temperature < 0) { // If there is an error with the TC, temperature will be < 0
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Serial.println("Thermocouple Error!!"); // There is a thermocouple error
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} else {
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Serial.print("Current Temperature: ");
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Serial.println( temperature ); // Print the temperature to Serial
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if (temperature != lastTemperature)
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gw.send(msg.setSensor(0).set(temperature, 1));
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lastTemperature = temperature;
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}
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gw.sleep(SLEEP_TIME);
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}

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