Diff: ADXL345HL.cpp

Revision:

0:441caaf895d8

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ADXL345HL.cpp	Tue Apr 29 00:04:48 2014 +0000
@@ -0,0 +1,90 @@
+#include "ADXL345HL.h"
+
+void ADXL345HL::init(int calibsamples, int readsampls, float samplrate)
+{
+    accelerometer=new ADXL345_I2C(p28,p27);
+    calibrationsamples=calibsamples;
+    readsamples=readsampls;
+    samplerate=samplrate;
+    output=new double[3];
+    //Go into standby mode to configure the device.
+    accelerometer->setPowerControl(0x00);
+    wait(0.001);
+    //Full resolution, +/-16g, 4mg/LSB.
+    accelerometer->setDataFormatControl(0x0B);
+    wait(0.001);
+    //200Hz data rate.
+    accelerometer->setDataRate(ADXL345_200HZ);
+    wait(0.001);
+    //Measurement mode.
+    accelerometer->setPowerControl(0x08);
+    //See http://www.analog.com/static/imported-files/application_notes/AN-1077.pdf
+    wait_ms(22);
+}
+
+void ADXL345HL::calibrateAccelerometer(void)
+{
+
+    double a_xAccumulator = 0;
+    double a_yAccumulator = 0;
+    double a_zAccumulator = 0;
+
+    //Take a number of readings and average them
+    //to calculate the zero g offset.
+    for (int i = 0; i < calibrationsamples; i++) {
+
+        accelerometer->getOutput(readings);
+
+        a_xAccumulator += (int16_t) readings[0];
+        a_yAccumulator += (int16_t) readings[1];
+        a_zAccumulator += (int16_t) readings[2];
+
+        wait(samplerate);
+
+    }
+
+    a_xAccumulator /= calibrationsamples;
+    a_yAccumulator /= calibrationsamples;
+    a_zAccumulator /= calibrationsamples;
+
+    //At 4mg/LSB, 250 LSBs is 1g.
+    xBias = a_xAccumulator;
+    yBias = a_yAccumulator;
+    zBias=a_zAccumulator;
+    //zBias = (a_zAccumulator - 250);
+
+    a_xAccumulator = 0;
+    a_yAccumulator = 0;
+    a_zAccumulator = 0;
+}
+
+
+double* ADXL345HL::sampleAccelerometer(void)
+{
+    double a_xAccumulator = 0;
+    double a_yAccumulator = 0;
+    double a_zAccumulator = 0;
+    for (int i=0; i<readsamples; ++i) {
+        accelerometer->getOutput(readings);
+        a_xAccumulator += (int16_t) readings[0];
+        a_yAccumulator += (int16_t) readings[1];
+        a_zAccumulator += (int16_t) readings[2];
+    }
+    //Average the samples, remove the bias, and calculate the acceleration
+    //in m/s/s.
+    output[0] = ((a_xAccumulator / readsamples) - xBias) * ACCELEROMETER_GAIN;
+    output[1] = ((a_yAccumulator / readsamples) - yBias) * ACCELEROMETER_GAIN;
+    output[2] = ((a_zAccumulator / readsamples) - zBias) * ACCELEROMETER_GAIN;
+    return output;
+}
+
+
+ADXL345HL::ADXL345HL()
+{
+}
+
+ADXL345HL::~ADXL345HL()
+{
+    delete[] output;
+    delete accelerometer;
+}
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