Michael Lange / MPL3115A2

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

Download repository: zip gz

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 revision 3:7c7c1ea6fc33

Name Size Actions
[up]
Altitude.cpp 1243 Revisions Annotate
Altitude.h 2339 Revisions Annotate
MPL3115A2.cpp 7245 Revisions Annotate
MPL3115A2.h 12542 Revisions Annotate
Pressure.cpp 1656 Revisions Annotate
Pressure.h 1828 Revisions Annotate
Temperature.cpp 1343 Revisions Annotate
Temperature.h 1876 Revisions Annotate

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