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lib/SFE_BMP180/examples/BMP180_altitude_example/BMP180_altitude_example.ino

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+/* SFE_BMP180 altitude example sketch
+
+This sketch shows how to use the Bosch BMP180 pressure sensor
+as an altimiter.
+https://www.sparkfun.com/products/11824
+
+Like most pressure sensors, the BMP180 measures absolute pressure.
+Since absolute pressure varies with altitude, you can use the pressure
+to determine your altitude.
+
+Because pressure also varies with weather, you must first take a pressure
+reading at a known baseline altitude. Then you can measure variations
+from that pressure
+
+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
+*/
+
+// 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;
+
+double baseline; // baseline pressure
+
+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 (disconnected?)\n\n");
+    while(1); // Pause forever.
+  }
+
+  // Get the baseline pressure:
+  
+  baseline = getPressure();
+  
+  Serial.print("baseline pressure: ");
+  Serial.print(baseline);
+  Serial.println(" mb");  
+}
+
+void loop()
+{
+  double a,P;
+  
+  // Get a new pressure reading:
+
+  P = getPressure();
+
+  // Show the relative altitude difference between
+  // the new reading and the baseline reading:
+
+  a = pressure.altitude(P,baseline);
+  
+  Serial.print("relative altitude: ");
+  if (a >= 0.0) Serial.print(" "); // add a space for positive numbers
+  Serial.print(a,1);
+  Serial.print(" meters, ");
+  if (a >= 0.0) Serial.print(" "); // add a space for positive numbers
+  Serial.print(a*3.28084,0);
+  Serial.println(" feet");
+  
+  delay(500);
+}
+
+
+double getPressure()
+{
+  char status;
+  double T,P,p0,a;
+
+  // 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.
+    // Use '&T' to provide the address of T to the function.
+    // Function returns 1 if successful, 0 if failure.
+
+    status = pressure.getTemperature(T);
+    if (status != 0)
+    {
+      // 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.
+        // Use '&P' to provide the address of 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)
+        {
+          return(P);
+        }
+        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");
+}
+
+
+