upm: enable MMC35240 3-axis magnetic sensor library and example

MMC35240 is 3-axis magnetic sensor from MEMSIC.

This sensor can measure magnetic fields within the full scale range of
+-24 Gauss (G).

The library provided is libupm-mmc35240.so
The example provided is mmc35240-example-cxx where it will print x,y,z axis
when trigger buffer data is ready. It's also print azimuth value.

This sensor requires calibration. Please shake the sensor in figure 8 pattern,
mmc35240-example will print the calibrated level.

As the sensor data is noisy, we have implemented denoise algorithm within the
sensor library.

The azimuth formula is provided by Han, He <he.han@intel.com>.

Signed-off-by: Lay, Kuan Loon <kuan.loon.lay@intel.com>
Signed-off-by: Mihai Tudor Panu <mihai.tudor.panu@intel.com>

examples/c++/CMakeLists.txt

@@ -333,6 +333,7 @@ add_example (sensortemplate)
 add_example (p9813)
 add_example (abpdrrt005pg2a5)
 add_example (lcdks)
+add_example (mmc35240)
 
 # These are special cases where you specify example binary, source file and module(s)
 include_directories (${PROJECT_SOURCE_DIR}/src)

examples/c++/mmc35240.cxx

@@ -0,0 +1,111 @@
+/*
+ * Author: Lay, Kuan Loon <kuan.loon.lay@intel.com>
+ * Copyright (c) 2016 Intel Corporation.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+#include <iostream>
+#include <unistd.h>
+#include <signal.h>
+#include <math.h>
+#include "mmc35240.hpp"
+
+using namespace std;
+
+int shouldRun = true;
+upm::MMC35240* magnetometer;
+
+void
+sig_handler(int signo)
+{
+    if (signo == SIGINT)
+        shouldRun = false;
+}
+
+void
+data_callback(char* data)
+{
+    float x, y, z;
+    double azimuth;
+    int level;
+    magnetometer->extract3Axis(data, &x, &y, &z);
+    /* calibrated level
+     * UNRELIABLE = 0
+     * ACCURACY_LOW = 1
+     * ACCURACY_MEDIUM = 2
+     * ACCURACY_HIGH = >=3
+     */
+    level = magnetometer->getCalibratedLevel();
+
+    if ((x == 0) && (y == 0)) {
+        cout << "Point (0, 0) is invalid!\n" << endl;
+        return;
+    }
+
+    if (x == 0) {
+        if (y > 0)
+            azimuth = 0;
+        else
+            azimuth = 180;
+    } else if (y == 0) {
+        if (x > 0)
+            azimuth = 90;
+        else
+            azimuth = 270;
+    } else {
+        if (x > 0)
+            azimuth = 90 - atan(y / x) * 180 / M_PI;
+        else
+            azimuth = 270 - atan(y / x) * 180 / M_PI;
+    }
+
+    cout << "[Calibrated Level:" << level << ']' << "[Azimuth:" << (int) (360 - azimuth) << ']'
+         << '\t' << (int) x << '\t' << (int) y << '\t' << (int) z << "[uT]" << endl;
+}
+
+int
+main()
+{
+    signal(SIGINT, sig_handler);
+    //! [Interesting]
+    // Instantiate a MMC35240 Magnetic Sensor on iio device 5. This configuration is a reference and
+    // should be changed per platform/board type.
+    magnetometer = new upm::MMC35240(5);
+    // Kernel driver does not allow changing the value of scale at run-time, default scale is
+    // 0.001000
+    magnetometer->setScale(0.001000);
+    // Available sampling frequency are 1.5, 13, 25, 50
+    magnetometer->setSamplingFrequency(25.000000);
+    magnetometer->enable3AxisChannel();
+    magnetometer->installISR(data_callback, NULL);
+    magnetometer->enableBuffer(16);
+
+    while (shouldRun) {
+        sleep(1);
+    }
+    magnetometer->disableBuffer();
+
+    //! [Interesting]
+    cout << "Exiting" << endl;
+
+    delete magnetometer;
+
+    return 0;
+}