Reading from BMP180, HMC5883L, and other sensors in one sketch

joemcconnell · February 22, 2017, 2:38am

Hello,

New to Arduino here and I am having trouble understanding how to read data from multiple sensors connected to my Arduino. I've got a BMP180, HMC5883L, among others, that I have the example sketches for. I've opened the Wire library to begin reading from I2C addresses of each of the sensors, but I do not understand how the data registers work or how to call data from each address. Could someone be kind enough to help me get started?

I have attached my code below.

Sketch:

#include <Wire.h> //I2C Arduino library
#include <Adafruit_HMC5883_U.h>
#include <SFE_BMP180.h> //BMP180 library

#define HMC 0x1E //I2C address for HMC5883L magnetometer
#define BMP 0x77 //I2C address for BMP180 pressure, altitude, and temperature sensor

void setup() {
Serial.begin(9600);
Wire.begin;

Wire.beginTransmission(HMC); //start talking to HMC
Wire.write(0x02); //set register
Wire.write(0x00); //tell HMC to continuously measure
Wire.endTransmission();

}

void loop() {

//HMC data retrieval and print to SerialMontior
int x,y,z; //triple axis data

//Tell the HMC what regist to begin writing data into
Wire.beginTransmission(addr);
Wire.write(0x03); //start with register 3.
Wire.endTransmission();

//Read the data.. 2 bytes for each axis.. 6 total bytes
Wire.requestFrom(addr, 6);
if(6<=Wire.available()){
x = Wire.read()<<8; //MSB x
x |= Wire.read(); //LSB x
z = Wire.read()<<8; //MSB z
z |= Wire.read(); //LSB z
y = Wire.read()<<8; //MSB y
y |= Wire.read(); //LSB y
}

// Show Values
Serial.print("X Value: ");
Serial.println(x);
Serial.print("Y Value: ");
Serial.println(y);
Serial.print("Z Value: ");
Serial.println(z);
Serial.println();

delay(500);

//BMP data retrieval and print to SerialMonitor
//…. how do I handle the BMP’s temperature, pressure, etc.? I can import the library, but then what?

}

joemcconnell · February 24, 2017, 1:13am

My apologies on not posting my code properly. Here is the example sketch of the BMP:

/* SFE_BMP180 library example sketch

This sketch shows how to use the SFE_BMP180 library to read the
Bosch BMP180 barometric pressure sensor.
https://www.sparkfun.com/products/11824

Like most pressure sensors, the BMP180 measures absolute pressure.
This is the actual ambient pressure seen by the device, which will
vary with both altitude and weather.

Before taking a pressure reading you must take a temparture reading.
This is done with startTemperature() and getTemperature().
The result is in degrees C.

Once you have a temperature reading, you can take a pressure reading.
This is done with startPressure() and getPressure().
The result is in millibar (mb) aka hectopascals (hPa).

If you'll be monitoring weather patterns, you will probably want to
remove the effects of altitude. This will produce readings that can
be compared to the published pressure readings from other locations.
To do this, use the sealevel() function. You will need to provide
the known altitude at which the pressure was measured.

If you want to measure altitude, you will need to know the pressure
at a baseline altitude. This can be average sealevel pressure, or
a previous pressure reading at your altitude, in which case
subsequent altitude readings will be + or - the initial baseline.
This is done with the altitude() function.

Hardware connections:

- (GND) to GND
+ (VDD) to 3.3V

(WARNING: do not connect + to 5V or the sensor will be damaged!)

You will also need to connect the I2C pins (SCL and SDA) to your
Arduino. The pins are different on different Arduinos:

Any Arduino pins labeled:  SDA  SCL
Uno, Redboard, Pro:        A4   A5
Mega2560, Due:             20   21
Leonardo:                   2    3

Leave the IO (VDDIO) pin unconnected. This pin is for connecting
the BMP180 to systems with lower logic levels such as 1.8V

Have fun! -Your friends at SparkFun.

The SFE_BMP180 library uses floating-point equations developed by the
Weather Station Data Logger project: http://wmrx00.sourceforge.net/

Our example code uses the "beerware" license. You can do anything
you like with this code. No really, anything. If you find it useful,
buy me a beer someday.

V10 Mike Grusin, SparkFun Electronics 10/24/2013
V1.1.2 Updates for Arduino 1.6.4 5/2015
*/

// Your sketch must #include this library, and the Wire library.
// (Wire is a standard library included with Arduino.):

#include <SFE_BMP180.h>
#include <Wire.h>

// You will need to create an SFE_BMP180 object, here called "pressure":

SFE_BMP180 pressure;

#define ALTITUDE 1655.0 // Altitude of SparkFun's HQ in Boulder, CO. in meters

void setup()
{
  Serial.begin(9600);
  Serial.println("REBOOT");

  // Initialize the sensor (it is important to get calibration values stored on the device).

  if (pressure.begin())
    Serial.println("BMP180 init success");
  else
  {
    // Oops, something went wrong, this is usually a connection problem,
    // see the comments at the top of this sketch for the proper connections.

    Serial.println("BMP180 init fail\n\n");
    while(1); // Pause forever.
  }
}

void loop()
{
  char status;
  double T,P,p0,a;

  // Loop here getting pressure readings every 10 seconds.

  // If you want sea-level-compensated pressure, as used in weather reports,
  // you will need to know the altitude at which your measurements are taken.
  // We're using a constant called ALTITUDE in this sketch:
  
  Serial.println();
  Serial.print("provided altitude: ");
  Serial.print(ALTITUDE,0);
  Serial.print(" meters, ");
  Serial.print(ALTITUDE*3.28084,0);
  Serial.println(" feet");
  
  // If you want to measure altitude, and not pressure, you will instead need
  // to provide a known baseline pressure. This is shown at the end of the sketch.

  // You must first get a temperature measurement to perform a pressure reading.
  
  // Start a temperature measurement:
  // If request is successful, the number of ms to wait is returned.
  // If request is unsuccessful, 0 is returned.

  status = pressure.startTemperature();
  if (status != 0)
  {
    // Wait for the measurement to complete:
    delay(status);

    // Retrieve the completed temperature measurement:
    // Note that the measurement is stored in the variable T.
    // Function returns 1 if successful, 0 if failure.

    status = pressure.getTemperature(T);
    if (status != 0)
    {
      // Print out the measurement:
      Serial.print("temperature: ");
      Serial.print(T,2);
      Serial.print(" deg C, ");
      Serial.print((9.0/5.0)*T+32.0,2);
      Serial.println(" deg F");
      
      // Start a pressure measurement:
      // The parameter is the oversampling setting, from 0 to 3 (highest res, longest wait).
      // If request is successful, the number of ms to wait is returned.
      // If request is unsuccessful, 0 is returned.

      status = pressure.startPressure(3);
      if (status != 0)
      {
        // Wait for the measurement to complete:
        delay(status);

        // Retrieve the completed pressure measurement:
        // Note that the measurement is stored in the variable P.
        // Note also that the function requires the previous temperature measurement (T).
        // (If temperature is stable, you can do one temperature measurement for a number of pressure measurements.)
        // Function returns 1 if successful, 0 if failure.

        status = pressure.getPressure(P,T);
        if (status != 0)
        {
          // Print out the measurement:
          Serial.print("absolute pressure: ");
          Serial.print(P,2);
          Serial.print(" mb, ");
          Serial.print(P*0.0295333727,2);
          Serial.println(" inHg");

          // The pressure sensor returns abolute pressure, which varies with altitude.
          // To remove the effects of altitude, use the sealevel function and your current altitude.
          // This number is commonly used in weather reports.
          // Parameters: P = absolute pressure in mb, ALTITUDE = current altitude in m.
          // Result: p0 = sea-level compensated pressure in mb

          p0 = pressure.sealevel(P,ALTITUDE); // we're at 1655 meters (Boulder, CO)
          Serial.print("relative (sea-level) pressure: ");
          Serial.print(p0,2);
          Serial.print(" mb, ");
          Serial.print(p0*0.0295333727,2);
          Serial.println(" inHg");

          // On the other hand, if you want to determine your altitude from the pressure reading,
          // use the altitude function along with a baseline pressure (sea-level or other).
          // Parameters: P = absolute pressure in mb, p0 = baseline pressure in mb.
          // Result: a = altitude in m.

          a = pressure.altitude(P,p0);
          Serial.print("computed altitude: ");
          Serial.print(a,0);
          Serial.print(" meters, ");
          Serial.print(a*3.28084,0);
          Serial.println(" feet");
        }
        else Serial.println("error retrieving pressure measurement\n");
      }
      else Serial.println("error starting pressure measurement\n");
    }
    else Serial.println("error retrieving temperature measurement\n");
  }
  else Serial.println("error starting temperature measurement\n");

  delay(5000);  // Pause for 5 seconds.
}

joemcconnell · February 24, 2017, 7:11pm

Here is what I came up with so far, but I receive piles of error messages when I try to compile. Anyone willing to help me out?

#include <Wire.h> //I2C Arduino library
#include <Adafruit_Sensor.h> //Adafruit Sensor library
#include <Adafruit_HMC5883_U.h> //HMC5883L library
#include <SFE_BMP180.h> //BMP180 library

// Declare sensor I2C addresses and instance names

#define hmc (0x1E)); //I2C address for HMC5883L magnetometer
#define bmp (0x77)); //I2C address for BMP180 pressure, altitude, and temperature sensor


void setup() {
  Serial.begin(9600);
  Serial.println("CANSAT Glider Version 0.1");

if (!hmc.begin()) {
  Serial.println("Could not find HMC5883L sensor, check wiring!");
  while(1);
  }
if (!bmp.begin()) {
  Serial.println("Could not find BMP180 sensor, check wiring!");
  while(1);
  }
if (!rtc.begin()) {
  Serial.println("Could not find RTC, check wiring!");
  while(1);
  }
  
Serial.println("All sensors initialized.");

}

void loop() {

// HMC data retrieval and print to SerialMonitor

Serial.println("HMC");

sensors_event_t event;
hmc.getEvent(&event);

  /* Display the results (magnetic vector values are in micro-Tesla (uT)) */
  Serial.print("X: "); Serial.print(event.magnetic.x); Serial.print("  ");
  Serial.print("Y: "); Serial.print(event.magnetic.y); Serial.print("  ");
  Serial.print("Z: "); Serial.print(event.magnetic.z); Serial.print("  ");Serial.println("uT");

  // Hold the module so that Z is pointing 'up' and you can measure the heading with x&y
  // Calculate heading when the magnetometer is level, then correct for signs of axis.
float heading = atan2(event.magnetic.y, event.magnetic.x);
  
  // Convert radians to degrees for readability.
  float headingDegrees = heading * 180/M_PI; 
  
  Serial.print("Heading (degrees): "); Serial.println(headingDegrees);
  
  delay(500);



//BMP data retrieval and print to SerialMonitor

 char status;
 double T, P, p0, a;
 
  // Loop here getting pressure readings every 10 seconds.

  // If you want sea-level-compensated pressure, as used in weather reports,
  // you will need to know the altitude at which your measurements are taken.
  // We're using a constant called ALTITUDE in this sketch:
  
  Serial.println();
  Serial.print("provided altitude: ");
  Serial.print(ALTITUDE,0);
  Serial.print(" meters, ");
  Serial.print(ALTITUDE*3.28084,0);
  Serial.println(" feet");
  
  // If you want to measure altitude, and not pressure, you will instead need
  // to provide a known baseline pressure. This is shown at the end of the sketch.

  // You must first get a temperature measurement to perform a pressure reading.
  
  // Start a temperature measurement:
  // If request is successful, the number of ms to wait is returned.
  // If request is unsuccessful, 0 is returned.

  status = bmp.startTemperature();
  if (status != 0)
  {
    // Wait for the measurement to complete:
    delay(status);

    // Retrieve the completed temperature measurement:
    // Note that the measurement is stored in the variable T.
    // Function returns 1 if successful, 0 if failure.

    status = bmp.getTemperature(T);
    if (status != 0)
    {
      // Print out the measurement:
      Serial.print("temperature: ");
      Serial.print(T,2);
      Serial.print(" deg C, ");
      Serial.print((9.0/5.0)*T+32.0,2);
      Serial.println(" deg F");
      
      // Start a pressure measurement:
      // The parameter is the oversampling setting, from 0 to 3 (highest res, longest wait).
      // If request is successful, the number of ms to wait is returned.
      // If request is unsuccessful, 0 is returned.

      status = bmp.startPressure(3);
      if (status != 0)
      {
        // Wait for the measurement to complete:
        delay(status);

        // Retrieve the completed pressure measurement:
        // Note that the measurement is stored in the variable P.
        // Note also that the function requires the previous temperature measurement (T).
        // (If temperature is stable, you can do one temperature measurement for a number of pressure measurements.)
        // Function returns 1 if successful, 0 if failure.

        status = bmp.getPressure(P,T);
        if (status != 0)
        {
          // Print out the measurement:
          Serial.print("absolute pressure: ");
          Serial.print(P,2);
          Serial.print(" mb, ");
          Serial.print(P*0.0295333727,2);
          Serial.println(" inHg");

          // The pressure sensor returns abolute pressure, which varies with altitude.
          // To remove the effects of altitude, use the sealevel function and your current altitude.
          // This number is commonly used in weather reports.
          // Parameters: P = absolute pressure in mb, ALTITUDE = current altitude in m.
          // Result: p0 = sea-level compensated pressure in mb

          p0 = bmp.sealevel(P,ALTITUDE); // we're at 1655 meters (Boulder, CO)
          Serial.print("relative (sea-level) pressure: ");
          Serial.print(p0,2);
          Serial.print(" mb, ");
          Serial.print(p0*0.0295333727,2);
          Serial.println(" inHg");

          // On the other hand, if you want to determine your altitude from the pressure reading,
          // use the altitude function along with a baseline pressure (sea-level or other).
          // Parameters: P = absolute pressure in mb, p0 = baseline pressure in mb.
          // Result: a = altitude in m.

          a = bmp.altitude(P,p0);
          Serial.print("computed altitude: ");
          Serial.print(a,0);
          Serial.print(" meters, ");
          Serial.print(a*3.28084,0);
          Serial.println(" feet");
        }
        else Serial.println("error retrieving pressure measurement\n");
      }
      else Serial.println("error starting pressure measurement\n");
    }
    else Serial.println("error retrieving temperature measurement\n");
  }
  else Serial.println("error starting temperature measurement\n");

  delay(5000);  // Pause for 5 seconds.

}

system · February 24, 2017, 7:17pm

#define hmc (0x1E)); Unless you really know what you're doing, never put a semicolon in a macro.
Fix that, then repost your code with the actual error messages you get.

joemcconnell · February 24, 2017, 7:22pm

Code with semicolons removed as you mentioned:

#include <Wire.h> //I2C Arduino library
#include <Adafruit_Sensor.h> //Adafruit Sensor library
#include <Adafruit_HMC5883_U.h> //HMC5883L library
#include <SFE_BMP180.h> //BMP180 library

// Declare sensor I2C addresses and instance names

#define hmc (0x1E) //I2C address for HMC5883L magnetometer
#define bmp (0x77) //I2C address for BMP180 pressure, altitude, and temperature sensor


void setup() {
  Serial.begin(9600);
  Serial.println("CANSAT Glider Version 0.1");

if (!hmc.begin()) {
  Serial.println("Could not find HMC5883L sensor, check wiring!");
  while(1);
  }
if (!bmp.begin()) {
  Serial.println("Could not find BMP180 sensor, check wiring!");
  while(1);
  }
  
Serial.println("All sensors initialized.");

}

void loop() {

// HMC data retrieval and print to SerialMonitor

Serial.println("HMC");

sensors_event_t event;
hmc.getEvent(&event);

  /* Display the results (magnetic vector values are in micro-Tesla (uT)) */
  Serial.print("X: "); Serial.print(event.magnetic.x); Serial.print("  ");
  Serial.print("Y: "); Serial.print(event.magnetic.y); Serial.print("  ");
  Serial.print("Z: "); Serial.print(event.magnetic.z); Serial.print("  ");Serial.println("uT");

  // Hold the module so that Z is pointing 'up' and you can measure the heading with x&y
  // Calculate heading when the magnetometer is level, then correct for signs of axis.
float heading = atan2(event.magnetic.y, event.magnetic.x);
  
  // Convert radians to degrees for readability.
  float headingDegrees = heading * 180/M_PI; 
  
  Serial.print("Heading (degrees): "); Serial.println(headingDegrees);
  
  delay(500);



//BMP data retrieval and print to SerialMonitor

 char status;
 double T, P, p0, a;
 
  // Loop here getting pressure readings every 10 seconds.

  // If you want sea-level-compensated pressure, as used in weather reports,
  // you will need to know the altitude at which your measurements are taken.
  // We're using a constant called ALTITUDE in this sketch:
  
  Serial.println();
  Serial.print("provided altitude: ");
  Serial.print(ALTITUDE,0);
  Serial.print(" meters, ");
  Serial.print(ALTITUDE*3.28084,0);
  Serial.println(" feet");
  
  // If you want to measure altitude, and not pressure, you will instead need
  // to provide a known baseline pressure. This is shown at the end of the sketch.

  // You must first get a temperature measurement to perform a pressure reading.
  
  // Start a temperature measurement:
  // If request is successful, the number of ms to wait is returned.
  // If request is unsuccessful, 0 is returned.

  status = bmp.startTemperature();
  if (status != 0)
  {
    // Wait for the measurement to complete:
    delay(status);

    // Retrieve the completed temperature measurement:
    // Note that the measurement is stored in the variable T.
    // Function returns 1 if successful, 0 if failure.

    status = bmp.getTemperature(T);
    if (status != 0)
    {
      // Print out the measurement:
      Serial.print("temperature: ");
      Serial.print(T,2);
      Serial.print(" deg C, ");
      Serial.print((9.0/5.0)*T+32.0,2);
      Serial.println(" deg F");
      
      // Start a pressure measurement:
      // The parameter is the oversampling setting, from 0 to 3 (highest res, longest wait).
      // If request is successful, the number of ms to wait is returned.
      // If request is unsuccessful, 0 is returned.

      status = bmp.startPressure(3);
      if (status != 0)
      {
        // Wait for the measurement to complete:
        delay(status);

        // Retrieve the completed pressure measurement:
        // Note that the measurement is stored in the variable P.
        // Note also that the function requires the previous temperature measurement (T).
        // (If temperature is stable, you can do one temperature measurement for a number of pressure measurements.)
        // Function returns 1 if successful, 0 if failure.

        status = bmp.getPressure(P,T);
        if (status != 0)
        {
          // Print out the measurement:
          Serial.print("absolute pressure: ");
          Serial.print(P,2);
          Serial.print(" mb, ");
          Serial.print(P*0.0295333727,2);
          Serial.println(" inHg");

          // The pressure sensor returns abolute pressure, which varies with altitude.
          // To remove the effects of altitude, use the sealevel function and your current altitude.
          // This number is commonly used in weather reports.
          // Parameters: P = absolute pressure in mb, ALTITUDE = current altitude in m.
          // Result: p0 = sea-level compensated pressure in mb

          p0 = bmp.sealevel(P,ALTITUDE); // we're at 1655 meters (Boulder, CO)
          Serial.print("relative (sea-level) pressure: ");
          Serial.print(p0,2);
          Serial.print(" mb, ");
          Serial.print(p0*0.0295333727,2);
          Serial.println(" inHg");

          // On the other hand, if you want to determine your altitude from the pressure reading,
          // use the altitude function along with a baseline pressure (sea-level or other).
          // Parameters: P = absolute pressure in mb, p0 = baseline pressure in mb.
          // Result: a = altitude in m.

          a = bmp.altitude(P,p0);
          Serial.print("computed altitude: ");
          Serial.print(a,0);
          Serial.print(" meters, ");
          Serial.print(a*3.28084,0);
          Serial.println(" feet");
        }
        else Serial.println("error retrieving pressure measurement\n");
      }
      else Serial.println("error starting pressure measurement\n");
    }
    else Serial.println("error retrieving temperature measurement\n");
  }
  else Serial.println("error starting temperature measurement\n");

  delay(5000);  // Pause for 5 seconds.

}

Error messages:

Arduino: 1.6.12 (Mac OS X), Board: "Arduino/Genuino Uno"

/Users/joe/Documents/Arduino/GLIDER/GLIDER.ino: In function 'void setup()':
GLIDER:16: error: request for member 'begin' in '30', which is of non-class type 'int'
 if (!hmc.begin()) {
          ^
GLIDER:20: error: request for member 'begin' in '119', which is of non-class type 'int'
 if (!bmp.begin()) {
          ^
/Users/joe/Documents/Arduino/GLIDER/GLIDER.ino: In function 'void loop()':
GLIDER:36: error: request for member 'getEvent' in '30', which is of non-class type 'int'
 hmc.getEvent(&event);
     ^
GLIDER:69: error: 'ALTITUDE' was not declared in this scope
   Serial.print(ALTITUDE,0);
                ^
GLIDER:83: error: request for member 'startTemperature' in '119', which is of non-class type 'int'
   status = bmp.startTemperature();
                ^
GLIDER:93: error: request for member 'getTemperature' in '119', which is of non-class type 'int'
     status = bmp.getTemperature(T);
                  ^
GLIDER:108: error: request for member 'startPressure' in '119', which is of non-class type 'int'
       status = bmp.startPressure(3);
                    ^
GLIDER:120: error: request for member 'getPressure' in '119', which is of non-class type 'int'
         status = bmp.getPressure(P,T);
                      ^
GLIDER:136: error: request for member 'sealevel' in '119', which is of non-class type 'int'
           p0 = bmp.sealevel(P,ALTITUDE); // we're at 1655 meters (Boulder, CO)
                    ^
GLIDER:148: error: request for member 'altitude' in '119', which is of non-class type 'int'
           a = bmp.altitude(P,p0);
                   ^
Multiple libraries were found for "Adafruit_Sensor.h"
 Used: /Users/joe/Documents/Arduino/libraries/Adafruit_Sensor
 Not used: /Users/joe/Documents/Arduino/libraries/Adafruit_Sensor-master
exit status 1
request for member 'begin' in '30', which is of non-class type 'int'

This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.

system · February 24, 2017, 7:27pm

This is what you wrote

#define hmc (0x1E)
...
void setup() {
...
if (!hmc.begin())

This what the compiler sees

void setup() {
...
if (!(0x1E).begin())

Can you see the problem?

joemcconnell · February 24, 2017, 7:38pm

So I need to switch them around? Put the I2C address before the name I'm assigning it?

system · February 24, 2017, 7:40pm

Please answer the question in reply #6.

joemcconnell · February 24, 2017, 7:53pm

Yes, I see the problem. I am really trying to get this working, so I tried to resolve the issue you pointed out but I haven't made any progress.

system · February 24, 2017, 7:56pm

Normally, you will create an object of the appropriate sensor class, and pass the constructor the I²C address, and then call the begin method of the object during setup().

Do you think you're trying to walk before you can crawl?

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