MPL3115A2 - Library to wrapper most of the functions on the M…

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Library to wrapper most of the functions on the MPL3115A2 pressure and temperature sensor.

Dependents: WeatherBalloon4180 WeatherBalloon4180 mbed_rifletool Smart_Watch_4180_Final_Design ... more

MPL3115A2 Precision Altimeter

This class wraps the functions of the MPL3115A2 sensor into a usable class that exposes most functions to your project. Functions that are not exposed can easily be added using the existing functions in this library. Specifically, I did not add any functions to handle FIFO logging or the use of either of the pin interrupts. This should not be too difficult to add if you need those features.

The motivation here was to get a set of support classes together that supported the chip and could be expanded on. With this library you can extract all relevant data from the sensor.

Be sure to download the DATASHEET and the App Note AN4519.

This library was created using the mbed NXP LPC11U24. Pins p27 and p28 were used for the I2C functions. Be sure to install 1K pull-up resistors on both lines. Also, if you're not using the SparkFun breakout board, be sure to use the right caps on the power pin. If you don't, the jitter can cause problems.

This library was inspired by the similar library available for the Arduino written by Nathan Seidle at SparkFun. I copied some of the number crunching routines and tried to follow his style of coding for the library. That way users of Arduinos could step into this library a little easier.

Below is some sample code that outputs the sensor data to a serial debug terminal window. If you have a logic analyzer, like the Saleae Logic, then you might not need the debug terminal window. If you still need the serial driver for your mbed, you can get it here.

Sample Code

#include "mbed.h"
#include "MPL3115A2.h"

I2C i2c(p28, p27);       // sda, scl

// Comment out all of the references to 'pc' on this page if you don't have the 
// serial debug driver for your mbed board installed on your computer. If you do,
// I personally like to use Putty as the terminal window to capture debug messages.
Serial pc(USBTX, USBRX); // tx, rx

// Again, remove the '&pc' parameter is you're not debugging.
MPL3115A2 sensor(&i2c, &pc);

DigitalOut myled(LED1);     // Sanity check to make sure the program is working.
DigitalOut powerPin(p21);   // <-- I powered the sensor from a pin. You don't have to.

int main() {
    
    powerPin = 1;
    wait_ms(300);

    pc.printf("** MPL3115A2 SENSOR **\r\n");

    sensor.init();

    pc.printf("Who Am I: 0x%X\r\n", sensor.whoAmI());

    Altitude a;
    Temperature t;
    Pressure p;
    
    // Offsets for Dacula, GA
    sensor.setOffsetAltitude(83);
    sensor.setOffsetTemperature(20);
    sensor.setOffsetPressure(-32);
    
    while(1) 
    {
        sensor.readAltitude(&a);
        sensor.readTemperature(&t);
        
        sensor.setModeStandby();
        sensor.setModeBarometer();
        sensor.setModeActive();
        sensor.readPressure(&p);
        
        pc.printf("Altitude: %sft, Temp: %sºF, Pressure: %sPa\r\n", a.print(), t.print(), p.print());
        pc.printf("OFF_H: 0x%X, OFF_T: 0x%X, OFF_P: 0x%X\r\n", sensor.offsetAltitude(), sensor.offsetTemperature(), sensor.offsetPressure());
    
        myled = 1;
        wait(5);
        myled = 0;
        wait(5);

        sensor.setModeStandby();
        sensor.setModeAltimeter();
        sensor.setModeActive();
    }
}

Files at this revision

API Documentation at this revision

Revision 0:beb43bc3d6d4, committed 2014-04-01

Comitter:: sophtware
Date:: Tue Apr 01 21:35:23 2014 +0000
Child:: 1:a011ae93a350
Commit message:: Initial Checkin

Changed in this revision

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Altitude.cpp	Tue Apr 01 21:35:23 2014 +0000
@@ -0,0 +1,64 @@
+#include "Altitude.h"
+#include "mbed.h"
+
+Altitude::Altitude()
+{
+    _altitude = 0.0;
+
+    _compressed[0] = 0;
+    _compressed[1] = 0;
+    _compressed[2] = 0;
+}
+
+Altitude::Altitude(float a, unitsType units)
+{
+    setAltitude(a, units);
+}
+    
+Altitude::Altitude(const char* compressed)
+{
+    setAltitude(compressed);
+}
+
+Altitude::Altitude(const char msb, const char csb, const char lsb)
+{
+    setAltitude(msb, csb, lsb);
+}
+
+void Altitude::setAltitude()
+{
+    setAltitude(_compressed[0], _compressed[1], _compressed[2]);
+}
+
+void Altitude::setAltitude(float a, unitsType units)
+{
+    // TODO:
+}
+    
+void Altitude::setAltitude(const char* compressed)
+{
+    setAltitude(compressed[0], compressed[1], compressed[2]);
+}
+
+void Altitude::setAltitude(const char msb, const char csb, const char lsb)
+{
+    float tempcsb = (lsb>>4) / 16.0;
+    _altitude = (float)((msb << 8) | csb) + tempcsb;
+}
+
+float Altitude::altitude(unitsType units)
+{
+    switch (units)
+    {
+        case FEET:
+            return MetersToFeet(_altitude);
+    }
+    
+    return _altitude;
+}
+
+const char* Altitude::print(unitsType units)
+{
+    sprintf(_printBuffer, "%.0f", altitude(units));
+    return _printBuffer;
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Altitude.h	Tue Apr 01 21:35:23 2014 +0000
@@ -0,0 +1,53 @@
+/*
+    MPL3115A2 Barometric Pressure and Tempurature Sensor Library
+    By: Michael Lange
+    Date: March 31, 2014
+    License: This code is public domain.
+ 
+    This class encapsulates an altitude reading from the sensor.
+ 
+ */
+ 
+ 
+#ifndef ALTITUDE_H
+#define ALTITUDE_H
+
+#include "mbed.h"
+
+// Casting truncates, therefore negative numbers become positive.
+// This will only cast properly in the range -128 to 127.
+#define float_to_char(x) (((x)<0)?(-(char)(x)):((char)(x)))
+
+class Altitude
+{
+public:
+
+    static const int size = 3;
+    enum unitsType { METERS, FEET };
+
+    Altitude();
+    Altitude(float a, unitsType units = FEET);
+    Altitude(const char* compressed);
+    Altitude(const char msb, const char csb, const char lsb);
+
+    operator char*(void) { return _compressed; }
+    operator float(void) { return _altitude; }
+
+    float altitude(unitsType units = FEET);
+    void setAltitude();
+    void setAltitude(const char* compressed);
+    void setAltitude(const char msb, const char csb, const char lsb);
+    void setAltitude(float a, unitsType units = FEET);
+
+    const char* print(unitsType units = FEET);
+    
+    static float MetersToFeet(float meters) { return meters * 3.28084; }
+    static float FeetToMeters(float feet) { return feet / 3.28084; }
+    
+private:
+    float _altitude;
+    char  _compressed[3];
+    char  _printBuffer[9];
+};
+
+#endif // ALTITUDE_H
\ No newline at end of file

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/MPL3115A2.cpp	Tue Apr 01 21:35:23 2014 +0000
@@ -0,0 +1,219 @@
+#include "MPL3115A2.h"
+#include "mbed.h"
+
+#include "stdarg.h" // For debugOut use of the ... parameter and va_list
+
+MPL3115A2::MPL3115A2(I2C *i2c, Serial *pc) : _i2c(i2c), _debug(pc)
+{
+}
+
+// By default I set the sensor to altimeter mode. I inserted a 1ms pause 
+// between each call to allow logic capture if needed. This give a small
+// gap between captures on the bus to make working with the data easier.
+void MPL3115A2::init()
+{
+    setModeStandby();
+    wait_ms(1);
+    setModeAltimeter();
+    wait_ms(1);
+    setOversampleRate(7);
+    wait_ms(1);
+    enableEventFlags();
+    wait_ms(1);
+    setModeActive();
+    wait_ms(1);
+}
+
+// This method wait for a specified amount of time for one of the data
+// ready flags to be set. You need to pass in the correct data ready
+// mask for this to work. See page 22 of the datasheet.
+int MPL3115A2::dataReady(const char mask)
+{
+    int attempts = 0;
+ 
+    while ((i2cRead(STATUS) & mask) == 0)
+    {
+        attempts++;
+        
+        if(attempts > MAX_DATA_READY_ATTEMPTS) 
+            return 0; // Failed
+            
+        wait_ms(1);
+    }
+    
+    return 1; // Success
+}
+
+Altitude* MPL3115A2::readAltitude(Altitude* a)
+{
+    // Force the sensor to take a new reading.
+    toggleOneShot();
+    
+    // Wait for the data to be ready.
+    if (!pressureDataReady())
+    {
+        debugOut("MPL3115A2::readAltitude: Sensor failed to generate an altitude reading in a reasonable time.\r\n");
+        
+        // We leave the altitude object as is if we encounter an error.
+        return a;
+    }
+        
+    // Get the new data from the sensor.
+    _i2c->start();                              // Start
+    if (_i2c->write(MPL3115A2_ADDRESS) != 1)    // A write to device
+        debugOut("MPL3115A2::readAltitude: Sensor failed to respond to write request at address 0x%X\r\n", MPL3115A2_ADDRESS);
+    
+    if (_i2c->write(OUT_P_MSB) != 1)            // Register to read
+        debugOut("MPL3115A2::readAltitude: Sensor at address 0x%X did not acknowledge register 0x%X\r\n", MPL3115A2_ADDRESS, OUT_P_MSB);
+    
+    // Write the data directly into our Altitude object. This object
+    // takes care of converting the compressed data from the sensor, and
+    // provides functions to get the data in various units. And it also
+    // has a print function to output the data as a string.
+    _i2c->read(MPL3115A2_ADDRESS, (*a), Altitude::size);
+    a->setAltitude();
+
+    return a;
+}
+
+// See readAltitude for comments about this function.
+Pressure* MPL3115A2::readPressure(Pressure* p)
+{
+    toggleOneShot();
+    
+    if (!pressureDataReady())
+    {
+        debugOut("MPL3115A2::readPressure: Sensor failed to generate a pressure reading in a reasonable time.\r\n");
+        return p;
+    }
+
+    _i2c->start(); 
+    if (_i2c->write(MPL3115A2_ADDRESS) != 1)
+        debugOut("MPL3115A2::readPressure: Sensor failed to respond to write request at address 0x%X\r\n", MPL3115A2_ADDRESS);
+    
+    if (_i2c->write(OUT_P_MSB) != 1) 
+        debugOut("MPL3115A2::readPressure: Sensor at address 0x%X did not acknowledge register 0x%X\r\n", MPL3115A2_ADDRESS, OUT_P_MSB);
+    
+    _i2c->read(MPL3115A2_ADDRESS, (*p), Pressure::size);
+    p->setPressure();
+
+    return p;
+}
+
+// See readAltitude for comments about this function.
+Temperature* MPL3115A2::readTemperature(Temperature* t)
+{
+    toggleOneShot();
+
+    if (!temperatureDataReady())
+    {
+        debugOut("MPL3115A2::readTemperature: Sensor failed to generate a temperature reading in a reasonable time.\r\n");
+        return t;
+    }
+
+    _i2c->start();  
+    if (_i2c->write(MPL3115A2_ADDRESS) != 1)
+        debugOut("MPL3115A2::readTemperature: Sensor failed to respond to write request at address 0x%X\r\n", MPL3115A2_ADDRESS);
+    
+    if (_i2c->write(OUT_T_MSB) != 1)        
+        debugOut("MPL3115A2::readTemperature: Sensor at address 0x%X did not acknowledge register 0x%X\r\n", MPL3115A2_ADDRESS, OUT_P_MSB);
+    
+    _i2c->read(MPL3115A2_ADDRESS, (*t), Temperature::size);
+    t->setTemperature();
+    
+    return t;
+}
+
+void MPL3115A2::setModeAltimeter()
+{
+    setRegisterBit(CTRL_REG1, 0x80);    // Set ALT bit
+}
+
+void MPL3115A2::setModeBarometer()
+{
+    clearRegisterBit(CTRL_REG1, 0x80);  // Clear ALT bit
+}
+
+void MPL3115A2::setModeStandby()
+{
+    clearRegisterBit(CTRL_REG1, 0x01);  // Clear SBYB bit for Standby mode
+}
+void MPL3115A2::setModeActive()
+{
+    setRegisterBit(CTRL_REG1, 0x01);    // Set SBYB bit for Active mode
+}
+
+void MPL3115A2::setOversampleRate(char sampleRate)
+{
+    if(sampleRate > 7) 
+        sampleRate = 7;                 // OS cannot be larger than 0b.0111
+    
+    sampleRate <<= 3;                   // Align it for the CTRL_REG1 register
+  
+    char temp = i2cRead(CTRL_REG1);     // Read current settings
+    temp &= 0xC7;                       // Clear out old OS bits
+    temp |= sampleRate;                 // Mask in new OS bits
+    i2cWrite(CTRL_REG1, temp);
+}
+
+void MPL3115A2::enableEventFlags()
+{
+    i2cWrite(PT_DATA_CFG, 0x07); // Enable all three pressure and temp event flags 
+}
+
+void MPL3115A2::toggleOneShot(void)
+{
+    clearRegisterBit(CTRL_REG1, 0x02);  // Clear OST bit
+    setRegisterBit(CTRL_REG1, 0x02);    // Set the OST bit.
+}
+
+void MPL3115A2::clearRegisterBit(const char regAddr, const char bitMask)
+{
+    char temp = i2cRead(regAddr);   // Read the current register value
+    temp &= ~bitMask;               // Clear the bit from the value
+    i2cWrite(regAddr, temp);        // Write register value back
+}
+
+void MPL3115A2::setRegisterBit(const char regAddr, const char bitMask)
+{
+    char temp = i2cRead(regAddr);   // Read the current register value
+    temp |= bitMask;                // Set the bit in the value
+    i2cWrite(regAddr, temp);        // Write register value back
+}
+
+char MPL3115A2::i2cRead(char regAddr)
+{
+    _i2c->start();                              // Start
+    if (_i2c->write(MPL3115A2_ADDRESS)!=1)      // A write to device
+        debugOut("MPL3115A2::i2cRead: Sensor failed to respond to write request at address 0x%X\r\n", MPL3115A2_ADDRESS);
+    
+    if (_i2c->write(regAddr)!=1)                // Register to read
+        debugOut("MPL3115A2::i2cRead: Sensor at address 0x%X did not acknowledge register 0x%X\r\n", MPL3115A2_ADDRESS, regAddr);
+    
+    _i2c->start();                  
+    if (_i2c->write(MPL3115A2_ADDRESS|0x01)!=1) // Read from device
+        debugOut("MPL3115A2::i2cRead: Sensor failed to respond to read request at address 0x%X\r\n", MPL3115A2_ADDRESS);
+
+    char result = _i2c->read(READ_NAK);         // Read the data
+    _i2c->stop();
+    
+    return result;  
+}
+
+void MPL3115A2::i2cWrite(char regAddr, char value)
+{
+    char cmd[2];
+    cmd[0] = regAddr;
+    cmd[1] = value;
+    if (_i2c->write(MPL3115A2_ADDRESS, cmd, 2) != 0)
+        debugOut("MPL3115A2::i2cWrite: Failed writing value (%d, 0x%X) to register 0x%X\r\n", value, regAddr);    
+}
+
+void MPL3115A2::debugOut(const char * format, ...)
+{
+    if (_debug == NULL)
+        return;
+        
+    va_list arg;
+    _debug->printf(format, arg);
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/MPL3115A2.h	Tue Apr 01 21:35:23 2014 +0000
@@ -0,0 +1,172 @@
+/*
+    MPL3115A2 Barometric Pressure and Tempurature Sensor Library
+    By: Michael Lange
+    Date: March 31, 2014
+    License: This code is public domain.
+ 
+    This class wraps the functions of the MPL3115A2 sensor into 
+    a usable class that exposes most functions to your project.
+    Functions that are not exposed can easily be added using the
+    existing functions in this library. Specifically, I did not
+    add any funtions to handle FIFO logging or the use of either
+    of the pin interrupts. This should not be too difficult to
+    add if you need those features.
+    
+    The motivation here was to get a set of support classes 
+    together that supported the chip and could be expanded on.
+    With this library you can extract all relevant data from the
+    sensor.
+    
+    Be sure to download the DATASHEET and the App Note AN4519.
+    
+    This libraray was created using the mbed NXP LPC11U24. Pins
+    p27 and p28 were used for the I2C functions. Be sure to install
+    1K pull-up resistors on both lines. Also, if you're not using
+    the SparkFun breakout board, be sure to use the right caps on 
+    the power pin. If you don't, the jitter can cause problems.
+    
+    This library was inspired by the similar library available for
+    the Arduino written by Nathan Seidle at SparkFun. I copied
+    some of the number crunching routines and tried to follow his
+    style of coding for the library. That way users of Arduinos
+    cound step into this library a little easier.
+ 
+ */
+ 
+ 
+#ifndef MPL3115A2_H
+#define MPL3115A2_H
+
+#include "mbed.h"
+
+#include "Altitude.h"               // Our classes to handle compressed data from the sensor.
+#include "Temperature.h"
+#include "Pressure.h"
+
+#define MPL3115A2_ADDRESS   0xC0    // Shifted 7-bit I2C address for sensor
+
+#define READ_ACK 1                  // For mbed I2C Read method.
+#define READ_NAK 0 
+
+#define MAX_DATA_READY_ATTEMPTS 512 // How many times we loop waiting for data before giving up.
+
+//      DEFINE             |REGISTER |RESET |RESET    |TYPE |AUTO-INC      |NAME/COMMENT
+//                         |         |      |STBY2ACT |     |ADDRESS       |
+#define STATUS              0x00 //  | 0x00 | Yes     | R   | 0x01         | Sensor Status Register (Alias for DR_STATUS or F_STATUS)
+#define OUT_P_MSB           0x01 //  | 0x00 | Yes     | R   | 0x02 | 0x01  | Pressure Data Out MSB (Bits 12-19 of 20-bit real-time Pressure sample | Root pointer t oPressure and Tempurature FIFO data)
+#define OUT_P_CSB           0x02 //  | 0x00 | Yes     | R   | 0x03         | Pressure Data out CSB (Bits 0-3 of 20-bit real-time Pressure sample)
+#define OUT_P_LSB           0x03 //  | 0x00 |         |     | 0x           |
+#define OUT_T_MSB           0x04 //  | 0x00 |         |     | 0x           |
+#define OUT_T_LSB           0x05 //  | 0x00 |         |     | 0x           |
+#define DR_STATUS           0x06 //  | 0x00 |         |     | 0x           |
+#define OUT_P_DELTA_MSB     0x07 //  | 0x00 |         |     | 0x           |
+#define OUT_P_DELTA_CSB     0x08 //  | 0x00 |         |     | 0x           |
+#define OUT_P_DELTA_LSB     0x09 //  | 0x00 |         |     | 0x           |
+#define OUT_T_DELTA_MSB     0x0A //  | 0x00 |         |     | 0x           |
+#define OUT_T_DELTA_LSB     0x0B //  | 0x00 |         |     | 0x           |
+#define WHO_AM_I            0x0C //  | 0xC4 |         |     | 0x           |
+#define F_STATUS            0x0D //  | 0x00 |         |     | 0x           |
+#define F_DATA              0x0E //  | 0x00 |         |     | 0x           |
+#define F_SETUP             0x0F //  | 0x00 |         |     | 0x           |
+#define TIME_DLY            0x10 //  | 0x00 |         |     | 0x           |
+#define SYSMOD              0x11 //  | 0x00 |         |     | 0x           |
+#define INT_SOURCE          0x12 //  | 0x00 |         |     | 0x           |
+#define PT_DATA_CFG         0x13 //  | 0x00 |         |     | 0x           |
+#define BAR_IN_MSB          0x14 //  | 0xC5 |         |     | 0x           |
+#define BAR_IN_LSB          0x15 //  | 0xE7 |         |     | 0x           |
+#define P_TGT_MSB           0x16 //  | 0x00 |         |     | 0x           |
+#define P_TGT_LSB           0x17 //  | 0x00 |         |     | 0x           |
+#define T_TGT               0x18 //  | 0x00 |         |     | 0x           |
+#define P_WND_MSB           0x19 //  | 0x00 |         |     | 0x           |
+#define P_WND_LSB           0x1A //  | 0x00 |         |     | 0x           |
+#define T_WND               0x1B //  | 0x00 |         |     | 0x           |
+#define P_MIN_MSB           0x1C //  | 0x00 |         |     | 0x           |
+#define P_MIN_CSB           0x1D //  | 0x00 |         |     | 0x           |
+#define P_MIN_LSB           0x1E //  | 0x00 |         |     | 0x           |
+#define T_MIN_MSB           0x1F //  | 0x00 |         |     | 0x           |
+#define T_MIN_LSB           0x20 //  | 0x00 |         |     | 0x           |
+#define P_MAX_MSB           0x21 //  | 0x00 |         |     | 0x           |
+#define P_MAX_CSB           0x22 //  | 0x00 |         |     | 0x           |
+#define P_MAX_LSB           0x23 //  | 0x00 |         |     | 0x           |
+#define T_MAX_MSB           0x24 //  | 0x00 |         |     | 0x           |
+#define T_MAX_LSB           0x25 //  | 0x00 |         |     | 0x           |
+#define CTRL_REG1           0x26 //  | 0x00 |         |     | 0x           |
+#define CTRL_REG2           0x27 //  | 0x00 |         |     | 0x           |
+#define CTRL_REG3           0x28 //  | 0x00 |         |     | 0x           |
+#define CTRL_REG4           0x29 //  | 0x00 |         |     | 0x           |
+#define CTRL_REG5           0x2A //  | 0x00 |         |     | 0x           |
+#define OFF_P               0x2B //  | 0x00 |         |     | 0x           |
+#define OFF_T               0x2C //  | 0x00 |         |     | 0x           |
+#define OFF_H               0x2D //  | 0x00 |         |     | 0x           |
+
+class MPL3115A2
+{
+public:
+    MPL3115A2(I2C *i2c, Serial *pc = NULL);
+
+    // Call this method in main to initialize the sensor.
+    void init();
+
+    // Returns the fixed device ID number (usually equal to 0xC4).
+    char  whoAmI() { return i2cRead(WHO_AM_I); } 
+    
+    Altitude* readAltitude(Altitude* a);            // Returns the altitude object with altitude
+    Pressure* readPressure(Pressure* p);            // Returns the pressure object with barometric pressure
+    Temperature* readTemperature(Temperature* t);   // Returns the temperature object with temperature
+    
+    // Use these methods to set the sensor's offsets to increase its accuracy. You can generally
+    // find your current altitude with a smart phone or GPS. Same goes for the temperature. For
+    // the current pressure where you are, you may need an accurate weather station. Getting the
+    // pressure from the web for your area is generally not close enough to help with calibration.
+    // You may need to play with the setting to achieve good accuracy. I found the offset steps
+    // were not 100% accurate to the datasheet and had to adjust accordingly. 
+    char offsetAltitude() { return i2cRead(OFF_H); }
+    void setOffsetAltitude(const char offset) { i2cWrite(OFF_H, offset); }      // -128 to 127 meters
+    char offsetPressure() { return i2cRead(OFF_P); }
+    void setOffsetPressure(const char offset) { i2cWrite(OFF_P, offset); }      // 4 Pa per LSB
+    char offsetTemperature() { return i2cRead(OFF_T); }
+    void setOffsetTemperature(const char offset) { i2cWrite(OFF_T, offset); }   // 0.0625ºC per LSB
+    
+    void  setModeStandby(); // Puts the sensor into Standby mode. Required when using methods below.
+    void  setModeActive();  // Activates the sensor to start taking measurements.
+    
+    // When calling any of these methods, be sure to put the sensor in standby mode first.
+    void  setModeBarometer();       // Puts the sensor into barometric mode
+    void  setModeAltimeter();       // Puts the sensor into altimeter mode
+    void  setOversampleRate(char);  // Sets the number of samples from 1 to 128.
+    void  enableEventFlags();       // Sets the all event flags.
+
+private:
+    I2C *_i2c;          // The I2C object we use to communicate with the sensor. It is not part
+                        // of the class so that it can be shared with other peripherals on the 
+                        // bus.
+    Serial *_debug;     // Set this in the constructor if you want the class to output debug messages.
+                        // If you need to pair down your code, you can remove this and all the
+                        // references to it in the code.
+ 
+    // Debug method that mimics the printf function, but will output nothing if _debug has not
+    // been set. This means you can safely us it in your code and nothing will happen if you don't
+    // assign the _debug object.
+    void debugOut(const char * format, ...);
+
+    // These are helper functions to SET or CLEAR bits. The mask should contain 1s in the position
+    // where the bits need to be set or cleared. One or more bits can be set or cleared this way.
+    void clearRegisterBit(const char regAddr, const char bitMask);
+    void setRegisterBit(const char regAddr, const char bitMask);
+
+    // Helper functions to check if data is ready in a register for either temperature or pressure.
+    // The pressureDataReady function works for both altitude and barometric pressure depending on 
+    // the mode the sensor is in.
+    int dataReady(const char mask);
+    int pressureDataReady() { return dataReady(0x04); }
+    int temperatureDataReady() { return dataReady(0x02); }
+ 
+    // Called to force the sensor to take another sample
+    void toggleOneShot();                       
+    
+    // Helper functions to read and write one value from the I2C bus using the sensor's address.
+    char i2cRead(char regAddr);
+    void i2cWrite(char regAddr, char value);
+};
+
+#endif // MPL3115A2_H

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Pressure.cpp	Tue Apr 01 21:35:23 2014 +0000
@@ -0,0 +1,73 @@
+#include "Pressure.h"
+#include "mbed.h"
+
+Pressure::Pressure()
+{
+    _pressure = 0.0;
+
+    _compressed[0] = 0;
+    _compressed[1] = 0;
+    _compressed[2] = 0;
+}
+
+Pressure::Pressure(float a, unitsType units)
+{
+    setPressure(a, units);
+}
+    
+Pressure::Pressure(const char* compressed)
+{
+    setPressure(compressed);
+}
+
+Pressure::Pressure(const char msb, const char csb, const char lsb)
+{
+    setPressure(msb, csb, lsb);
+}
+
+void Pressure::setPressure()
+{
+    setPressure(_compressed[0], _compressed[1], _compressed[2]);
+}
+
+void Pressure::setPressure(float a, unitsType units)
+{
+    // TODO:
+}
+    
+void Pressure::setPressure(const char* compressed)
+{
+    setPressure(compressed[0], compressed[1], compressed[2]);
+}
+
+void Pressure::setPressure(const char msb, const char csb, const char lsb)
+{
+    long pressure_whole = (long)msb<<16 | (long)csb<<8 | (long)lsb;
+    pressure_whole >>= 6; // Pressure is an 18 bit number with 2 bits of decimal. Get rid of decimal portion.
+
+    float pressure_decimal = (float)((lsb&0x30)>>4)/4.0; // Turn it into fraction
+
+    _pressure = (float)pressure_whole + pressure_decimal;
+}
+
+float Pressure::pressure(unitsType units)
+{
+    // http://www.asknumbers.com/
+    switch (units)
+    {
+        case PSI:
+            return _pressure * 0.000145037738;    
+        case INHG:
+            return _pressure * 0.00029529983071;
+        case MMHG:
+            return _pressure * 0.007500615613;
+    }
+    
+    return _pressure;
+}
+
+const char* Pressure::print(unitsType units)
+{
+    sprintf(_printBuffer, "%.0f", pressure(units));
+    return _printBuffer;
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Pressure.h	Tue Apr 01 21:35:23 2014 +0000
@@ -0,0 +1,46 @@
+/*
+    MPL3115A2 Barometric Pressure and Tempurature Sensor Library
+    By: Michael Lange
+    Date: March 31, 2014
+    License: This code is public domain.
+ 
+    This class encapsulates a pressure reading from the sensor.
+ 
+ */
+ 
+ 
+#ifndef PRESSURE_H
+#define PRESSURE_H
+
+#include "mbed.h"
+
+class Pressure
+{
+public:
+
+    static const int size = 3;
+    enum unitsType { PASCALS, PSI, INHG, MMHG };
+
+    Pressure();
+    Pressure(float a, unitsType units = PASCALS);
+    Pressure(const char* compressed);
+    Pressure(const char msb, const char csb, const char lsb);
+
+    operator char*(void) { return _compressed; }
+    operator float(void) { return _pressure; }
+
+    float pressure(unitsType units = PASCALS);
+    void setPressure();
+    void setPressure(const char* compressed);
+    void setPressure(const char msb, const char csb, const char lsb);
+    void setPressure(float a, unitsType units = PASCALS);
+
+    const char* print(unitsType units = PASCALS);
+    
+private:
+    float _pressure;
+    char  _compressed[3];
+    char  _printBuffer[9];
+};
+
+#endif // PRESSURE_H
\ No newline at end of file

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Temperature.cpp	Tue Apr 01 21:35:23 2014 +0000
@@ -0,0 +1,66 @@
+#include "Temperature.h"
+#include "mbed.h"
+
+Temperature::Temperature()
+{
+    _temperature = 0.0;
+
+    _compressed[0] = 0;
+    _compressed[1] = 0;
+}
+
+Temperature::Temperature(float t, unitsType units)
+{
+    setTemperature(t, units);
+}
+    
+Temperature::Temperature(const char* compressed)
+{
+    setTemperature(compressed);
+}
+
+Temperature::Temperature(const char msb, const char lsb)
+{
+    setTemperature(msb, lsb);
+}
+
+void Temperature::setTemperature()
+{
+    setTemperature(_compressed[0], _compressed[1]);
+}
+
+void Temperature::setTemperature(float t, unitsType units)
+{
+    // TODO:
+}
+    
+void Temperature::setTemperature(const char* compressed)
+{
+    setTemperature(compressed[0], compressed[1]);
+}
+
+void Temperature::setTemperature(const char msb, const char lsb)
+{
+    float templsb = (lsb>>4) / 16.0; //temp, fraction of a degree
+    _temperature = (float)(msb + templsb);
+}
+
+float Temperature::temperature(unitsType units)
+{
+    switch (units)
+    {
+        case FAHRENHEIT:
+            return (_temperature * 9.0)/ 5.0 + 32.0;
+        
+        case KELVIN:
+            return _temperature + 273.15;
+    }
+    
+    return _temperature;
+}
+
+const char* Temperature::print(unitsType units)
+{
+    sprintf(_printBuffer, "%.1f", temperature(units));
+    return _printBuffer;
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Temperature.h	Tue Apr 01 21:35:23 2014 +0000
@@ -0,0 +1,46 @@
+/*
+    MPL3115A2 Barometric Pressure and Tempurature Sensor Library
+    By: Michael Lange
+    Date: March 31, 2014
+    License: This code is public domain.
+ 
+    This class encapsulates a temperature reading from the sensor.
+ 
+ */
+ 
+ 
+#ifndef TEMPERATURE_H
+#define TEMPERATURE_H
+
+#include "mbed.h"
+
+class Temperature
+{
+public:
+
+    static const int size = 2;
+    enum unitsType { CELSIUS, FAHRENHEIT, KELVIN };
+
+    Temperature();
+    Temperature(float a, unitsType units = FAHRENHEIT);
+    Temperature(const char* compressed);
+    Temperature(const char msb, const char lsb);
+
+    operator char*(void) { return _compressed; }
+    operator float(void) { return _temperature; }
+
+    float temperature(unitsType units = FAHRENHEIT);
+    void setTemperature();
+    void setTemperature(const char* compressed);
+    void setTemperature(const char msb, const char lsb);
+    void setTemperature(float a, unitsType units = FAHRENHEIT);
+
+    const char* print(unitsType units = FAHRENHEIT);
+    
+private:
+    float _temperature;
+    char  _compressed[2];
+    char  _printBuffer[9];
+};
+
+#endif // TEMPERATURE_H
\ No newline at end of file

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Type:	Library
Created:	01 Apr 2014
Imports:	560
Forks:	8
Commits:	4
Dependents:	11
Dependencies:	0
Followers:	7

Altitude.cpp	Show annotated file Show diff for this revision Revisions of this file
Altitude.h	Show annotated file Show diff for this revision Revisions of this file
MPL3115A2.cpp	Show annotated file Show diff for this revision Revisions of this file
MPL3115A2.h	Show annotated file Show diff for this revision Revisions of this file
Pressure.cpp	Show annotated file Show diff for this revision Revisions of this file
Pressure.h	Show annotated file Show diff for this revision Revisions of this file
Temperature.cpp	Show annotated file Show diff for this revision Revisions of this file
Temperature.h	Show annotated file Show diff for this revision Revisions of this file