added getPT() to get both simultaneously

This can get both pressure and temperature simultaneously, saving a
little time and eliminating repetitive code in getPressure() and
getTemperature() while retaining the functionality.

Adafruit_MPL115A2.cpp

@@ -17,6 +17,7 @@
 
     v1.0 - First release
     v1.1 - Rick Sellens added casts to make bit shifts work below 22.6C
+         - get both P and T with a single call to getPT
 */
 /**************************************************************************/
 #if ARDUINO >= 100
@@ -65,10 +66,10 @@ void Adafruit_MPL115A2::readCoefficients() {
   Wire.endTransmission();
 
   Wire.requestFrom(MPL115A2_ADDRESS, 8);
-  a0coeff = ((i2cread() << 8) | i2cread());
-  b1coeff = ((i2cread() << 8) | i2cread());
-  b2coeff = ((i2cread() << 8) | i2cread());
-  c12coeff = (((i2cread() << 8) | i2cread())) >> 2;
+  a0coeff = (( (uint16_t) i2cread() << 8) | i2cread());
+  b1coeff = (( (uint16_t) i2cread() << 8) | i2cread());
+  b2coeff = (( (uint16_t) i2cread() << 8) | i2cread());
+  c12coeff = (( (uint16_t) (i2cread() << 8) | i2cread())) >> 2;
 
   /*  
   Serial.print("A0 = "); Serial.println(a0coeff, HEX);
@@ -120,31 +121,10 @@ void Adafruit_MPL115A2::begin() {
 */
 /**************************************************************************/
 float Adafruit_MPL115A2::getPressure() {
-  uint16_t 	pressure, temp;
-  float     pressureComp;
-
-  // Get raw pressure and temperature settings
-  Wire.beginTransmission(MPL115A2_ADDRESS);
-  i2cwrite((uint8_t)MPL115A2_REGISTER_STARTCONVERSION);
-  i2cwrite((uint8_t)0x00);
-  Wire.endTransmission();
-
-  // Wait a bit for the conversion to complete (3ms max)
-  delay(5);
-
-  Wire.beginTransmission(MPL115A2_ADDRESS);
-  i2cwrite((uint8_t)MPL115A2_REGISTER_PRESSURE_MSB);  // Register
-  Wire.endTransmission();
-
-  Wire.requestFrom(MPL115A2_ADDRESS, 4);
-  pressure = (( (uint16_t) i2cread() << 8) | i2cread()) >> 6;
-  temp = (( (uint16_t) i2cread() << 8) | i2cread()) >> 6;
+  float     pressureComp,centigrade;
 
-  // See datasheet p.6 for evaluation sequence
-  pressureComp = _mpl115a2_a0 + (_mpl115a2_b1 + _mpl115a2_c12 * temp ) * pressure + _mpl115a2_b2 * temp;
-
-  // Return pressure as floating point value
-  return ((65.0F / 1023.0F)*(float)pressureComp) + 50;
+  getPT(&pressureComp, &centigrade);
+  return pressureComp;
 }
 
 
@@ -154,6 +134,18 @@ float Adafruit_MPL115A2::getPressure() {
 */
 /**************************************************************************/
 float Adafruit_MPL115A2::getTemperature() {
+  float     pressureComp, centigrade;
+
+  getPT(&pressureComp, &centigrade);
+  return centigrade;
+}
+
+/**************************************************************************/
+/*!
+    @brief  Gets both at once and saves a little time
+*/
+/**************************************************************************/
+void Adafruit_MPL115A2::getPT(float *P, float *T) {
   uint16_t 	pressure, temp;
   float     pressureComp;
 
@@ -171,16 +163,17 @@ float Adafruit_MPL115A2::getTemperature() {
   Wire.endTransmission();
 
   Wire.requestFrom(MPL115A2_ADDRESS, 4);
-
   pressure = (( (uint16_t) i2cread() << 8) | i2cread()) >> 6;
   temp = (( (uint16_t) i2cread() << 8) | i2cread()) >> 6;
-  //Serial.print("t = "); Serial.println(temp, HEX);
-  float centigrade = temp;
-  centigrade -= 498;
-  centigrade /= -5.35;
-  centigrade += 25;
+
+  // See datasheet p.6 for evaluation sequence
+  pressureComp = _mpl115a2_a0 + (_mpl115a2_b1 + _mpl115a2_c12 * temp ) * pressure + _mpl115a2_b2 * temp;
+
+  // Return pressure and temperature as floating point values
+  *P = ((65.0F / 1023.0F) * pressureComp) + 50.0F;        // kPa
+  *T = ((float) temp - 498.0F) / -5.35F +25.0F;           // C
 
-  return centigrade;
 }
 
 
+

Adafruit_MPL115A2.h

@@ -55,6 +55,7 @@ class Adafruit_MPL115A2{
   void begin(void);
   float getPressure(void);
   float getTemperature(void);
+  void getPT(float *P, float *T);
 
  private:
   float _mpl115a2_a0;

examples/getPT/getPT.ino

@@ -0,0 +1,30 @@
+#include <Wire.h>
+#include <Adafruit_MPL115A2.h>
+
+Adafruit_MPL115A2 mpl115a2;
+
+void setup(void) 
+{
+  Serial.begin(9600);
+  Serial.println("Hello!");
+
+  Serial.println("Getting barometric pressure ...");
+  mpl115a2.begin();
+}
+
+void loop(void) 
+{
+  float pressureKPA = 0, temperatureC = 0;    
+
+  mpl115a2.getPT(&pressureKPA,&temperatureC);
+  Serial.print("Pressure (kPa): "); Serial.print(pressureKPA, 4); Serial.print(" kPa  ");
+  Serial.print("Temp (*C): "); Serial.print(temperatureC, 1); Serial.println(" *C both measured together");
+
+  pressureKPA = mpl115a2.getPressure();  
+  Serial.print("Pressure (kPa): "); Serial.print(pressureKPA, 4); Serial.println(" kPa");
+
+  temperatureC = mpl115a2.getTemperature();  
+  Serial.print("Temp (*C): "); Serial.print(temperatureC, 1); Serial.println(" *C");
+
+  delay(1000);
+}