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();
    }
}
Committer:
sophtware
Date:
Wed Apr 02 12:59:44 2014 +0000
Revision:
3:7c7c1ea6fc33
Updated documentation.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
sophtware 0:beb43bc3d6d4 1 #include "Temperature.h"
sophtware 0:beb43bc3d6d4 2 #include "mbed.h"
sophtware 0:beb43bc3d6d4 3
sophtware 0:beb43bc3d6d4 4 Temperature::Temperature()
sophtware 0:beb43bc3d6d4 5 {
sophtware 0:beb43bc3d6d4 6 _temperature = 0.0;
sophtware 0:beb43bc3d6d4 7
sophtware 0:beb43bc3d6d4 8 _compressed[0] = 0;
sophtware 0:beb43bc3d6d4 9 _compressed[1] = 0;
sophtware 0:beb43bc3d6d4 10 }
sophtware 0:beb43bc3d6d4 11
sophtware 0:beb43bc3d6d4 12 Temperature::Temperature(float t, unitsType units)
sophtware 0:beb43bc3d6d4 13 {
sophtware 0:beb43bc3d6d4 14 setTemperature(t, units);
sophtware 0:beb43bc3d6d4 15 }
sophtware 0:beb43bc3d6d4 16
sophtware 0:beb43bc3d6d4 17 Temperature::Temperature(const char* compressed)
sophtware 0:beb43bc3d6d4 18 {
sophtware 0:beb43bc3d6d4 19 setTemperature(compressed);
sophtware 0:beb43bc3d6d4 20 }
sophtware 0:beb43bc3d6d4 21
sophtware 0:beb43bc3d6d4 22 Temperature::Temperature(const char msb, const char lsb)
sophtware 0:beb43bc3d6d4 23 {
sophtware 0:beb43bc3d6d4 24 setTemperature(msb, lsb);
sophtware 0:beb43bc3d6d4 25 }
sophtware 0:beb43bc3d6d4 26
sophtware 0:beb43bc3d6d4 27 void Temperature::setTemperature()
sophtware 0:beb43bc3d6d4 28 {
sophtware 0:beb43bc3d6d4 29 setTemperature(_compressed[0], _compressed[1]);
sophtware 0:beb43bc3d6d4 30 }
sophtware 0:beb43bc3d6d4 31
sophtware 0:beb43bc3d6d4 32 void Temperature::setTemperature(float t, unitsType units)
sophtware 0:beb43bc3d6d4 33 {
sophtware 0:beb43bc3d6d4 34 // TODO:
sophtware 0:beb43bc3d6d4 35 }
sophtware 0:beb43bc3d6d4 36
sophtware 0:beb43bc3d6d4 37 void Temperature::setTemperature(const char* compressed)
sophtware 0:beb43bc3d6d4 38 {
sophtware 0:beb43bc3d6d4 39 setTemperature(compressed[0], compressed[1]);
sophtware 0:beb43bc3d6d4 40 }
sophtware 0:beb43bc3d6d4 41
sophtware 0:beb43bc3d6d4 42 void Temperature::setTemperature(const char msb, const char lsb)
sophtware 0:beb43bc3d6d4 43 {
sophtware 0:beb43bc3d6d4 44 float templsb = (lsb>>4) / 16.0; //temp, fraction of a degree
sophtware 0:beb43bc3d6d4 45 _temperature = (float)(msb + templsb);
sophtware 0:beb43bc3d6d4 46 }
sophtware 0:beb43bc3d6d4 47
sophtware 0:beb43bc3d6d4 48 float Temperature::temperature(unitsType units)
sophtware 0:beb43bc3d6d4 49 {
sophtware 0:beb43bc3d6d4 50 switch (units)
sophtware 0:beb43bc3d6d4 51 {
sophtware 0:beb43bc3d6d4 52 case FAHRENHEIT:
sophtware 0:beb43bc3d6d4 53 return (_temperature * 9.0)/ 5.0 + 32.0;
sophtware 0:beb43bc3d6d4 54
sophtware 0:beb43bc3d6d4 55 case KELVIN:
sophtware 0:beb43bc3d6d4 56 return _temperature + 273.15;
sophtware 0:beb43bc3d6d4 57 }
sophtware 0:beb43bc3d6d4 58
sophtware 0:beb43bc3d6d4 59 return _temperature;
sophtware 0:beb43bc3d6d4 60 }
sophtware 0:beb43bc3d6d4 61
sophtware 0:beb43bc3d6d4 62 const char* Temperature::print(unitsType units)
sophtware 0:beb43bc3d6d4 63 {
sophtware 0:beb43bc3d6d4 64 sprintf(_printBuffer, "%.1f", temperature(units));
sophtware 0:beb43bc3d6d4 65 return _printBuffer;
sophtware 0:beb43bc3d6d4 66 }