+ added offset for temperature (constant)

+ added demo4 + updated demo3

Author: RobTillaart

libraries/MAX31855/MAX31855.cpp

@@ -1,11 +1,16 @@
 //
 // FILE: MAX31855.cpp
 // AUTHOR: Rob Tillaart
-// VERSION: 0.1.01
+// VERSION: 0.1.02
 // PURPOSE: MAX31855 - Thermocouple
 // DATE: 2014-01-01
 // URL:
 //
+// HISTORY: 
+// 0.1.02 added offset
+// 0.1.01 refactored speed/performance
+// 0.1.00 initial version.
+//
 // Released to the public domain
 //
 
@@ -16,6 +21,7 @@ MAX31855::MAX31855(uint8_t sclk, uint8_t cs, uint8_t miso)
  _sclk = sclk;
  _cs = cs;
  _miso = miso;
+ _offset = 0;
 }
 
 void MAX31855::begin()
@@ -53,6 +59,7 @@ uint8_t MAX31855::read()
  // process temperature bit 18-31
  _temperature = (value & 0x1FFF) * 0.25;
  if (value & 0x2000) _temperature *= -1;
+ if (_offset != 0) _temperature += _offset;
 
  return _status;
 }
@@ -67,8 +74,10 @@ uint32_t MAX31855::_read(void)
  {
  value <<= 1;
  digitalWrite(_sclk, LOW);
+ // delayMicroseconds(1); // DUE
  if ( digitalRead(_miso) ) value += 1;
  digitalWrite(_sclk, HIGH);
+ // delayMicroseconds(1); // DUE
  }
 
  digitalWrite(_cs, HIGH);

libraries/MAX31855/MAX31855.h

@@ -3,7 +3,7 @@
 //
 // FILE: MAX31855.h
 // AUTHOR: Rob Tillaart
-// VERSION: 0.1.01
+// VERSION: 0.1.02
 // PURPOSE: MAX31855 - Thermocouple
 // DATE: 2014-01-01
 // URL:
@@ -17,7 +17,7 @@
 #include "Arduino.h"
 #endif
 
-#define MAX31855_VERSION "0.1.01"
+#define MAX31855_VERSION "0.1.02"
 
 #define STATUS_OK 0x00
 #define STATUS_OPEN_CIRCUIT 0x01
@@ -32,14 +32,19 @@ class MAX31855
  uint8_t read();
  float getInternal(void) { return _internal; };
  // Celsius
- float getTemperature(void) { return _temperature; } ;
- uint8_t getStatus(void) {return _status; } ;
+ float getTemperature(void) { return _temperature; };
+ uint8_t getStatus(void) {return _status; };
+ 
+ void setOffset(float t) { _offset = t; };
+ float getOffset(float t) { return _offset; };
+ 
 
 private:
  uint32_t _read();
  float _internal;
  float _temperature;
  uint8_t _status;
+ float _offset;
 
  uint8_t _sclk;
  uint8_t _miso;

libraries/MAX31855/examples/max31855_demo3/max31855_demo3.ino

@@ -1,5 +1,5 @@
 //
-// FILE: max31855_demo2.ino
+// FILE: max31855_demo3.ino
 // AUTHOR: Rob Tillaart
 // VERSION: 0.1.01
 // PURPOSE: thermocouple lib demo application
@@ -20,16 +20,16 @@ MAX31855 tc(clPin, csPin, doPin);
 void setup() 
 {
  Serial.begin(115200);
- Serial.print("Start max31855_demo: ");
+ Serial.print("Start max31855_demo3: ");
  Serial.println(MAX31855_VERSION);
  Serial.println();
 
  tc.begin();
 
  uint32_t start = micros();
- tc.read();
+ for (int i=0; i< 10; i++) tc.read();
  uint32_t stop = micros();
- Serial.print("read:\t");
+ Serial.print("10x read:\t");
  Serial.println(stop - start);
 
  start = micros();
@@ -39,19 +39,46 @@ void setup()
  Serial.println(stop - start);
 
  start = micros();
- tc.getInternal();
+ float t2 = tc.getInternal();
  stop = micros();
  Serial.print("getInternal:\t");
  Serial.println(stop - start);
 
- Serial.println(t1,2);
+ Serial.println();
+ Serial.println(t1, 2);
+ Serial.println(t2, 2);
+ Serial.println();
 }
 
 void loop() 
 {
+ // this loop returns multiples of about 73mSec (counter multiples of ~143)
+ // so the # measurements per second is about 14?
+ uint32_t counter = 0;
+ float t1 = tc.getTemperature();
+ float t2 = t1;
+
+ uint32_t start = micros();
+ while (t2 == t1)
+ {
+ tc.read();
+ t1 = tc.getTemperature();
+ counter++;
+ }
+ uint32_t stop = micros();
+
+ Serial.print("change:\t");
+ Serial.println(stop - start);
+ Serial.print("counter:\t");
+ Serial.println(counter);
+ Serial.println(t2, 2);
+ Serial.println(t1, 2);
+ Serial.println();
 }
 
 
 
 
 
+
+

libraries/MAX31855/examples/max31855_demo4/max31855_demo4.ino

@@ -0,0 +1,80 @@
+//
+// FILE: max31855_demo4.ino
+// AUTHOR: Rob Tillaart
+// VERSION: 0.1.00
+// PURPOSE: thermocouple lib demo application
+// DATE: 2014-01-02
+// URL:
+//
+// Released to the public domain
+//
+
+#include "MAX31855.h"
+
+const int doPin = 7;
+const int csPin = 6;
+const int clPin = 5;
+
+MAX31855 tc(clPin, csPin, doPin);
+
+void setup() 
+{
+ Serial.begin(115200);
+ Serial.print("Start max31855_demo4: ");
+ Serial.println(MAX31855_VERSION);
+ Serial.println();
+
+ tc.begin();
+
+ uint32_t start = micros();
+ for (int i=0; i< 10; i++) tc.read();
+ uint32_t stop = micros();
+ Serial.print("10x read:\t");
+ Serial.println(stop - start);
+
+
+ start = micros();
+ float t1 = tc.getTemperature();
+ stop = micros();
+ Serial.print("getTemperature:\t");
+ Serial.println(stop - start);
+ Serial.println(t1, 2);
+ Serial.println();
+
+
+ start = micros();
+ tc.setOffset(2.0);
+ stop = micros();
+ Serial.print("setOffset:\t");
+ Serial.println(stop - start);
+
+ tc.read();
+ start = micros();
+ t1 = tc.getTemperature();
+ stop = micros();
+ Serial.print("getTemperature:\t");
+ Serial.println(stop - start);
+ Serial.println(t1, 2);
+ Serial.println();
+
+
+ start = micros();
+ float t2 = tc.getInternal();
+ stop = micros();
+ Serial.print("getInternal:\t");
+ Serial.println(stop - start);
+ Serial.println(t2, 4);
+ Serial.println();
+}
+
+void loop() 
+{
+}
+
+
+
+
+
+
+
+