mpu9150: rewrite from scratch

This driver has been rewritten from scratch.  It is implemented as 3
seperate drivers now (but all included as part of the mpu9150 UPM
library):

AK8975 (Magnetometer)
MPU60X0 (Accelerometer, Gyroscope, and Temperature sensor)
MPU9150 (composed of AK8975 and MPU60X0)

Each driver can be used independently and includes examples in
C++/JS/Python.

Commonly used capabilities are supported, and methods/register
definitions exist to easily implement any desired functionality that
is missing.  Interrupt support has also been added.

Scaling support has also been properly implemented for both the
Accelerometer and Gyroscope.

Signed-off-by: Jon Trulson <jtrulson@ics.com>
Signed-off-by: Mihai Tudor Panu <mihai.tudor.panu@intel.com>

src/mpu9150/ak8975.cxx

@@ -0,0 +1,232 @@
+/*
+ * Author: Jon Trulson <jtrulson@ics.com>
+ * Copyright (c) 2015 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 <unistd.h>
+#include <iostream>
+#include <string>
+
+#include "ak8975.h"
+
+using namespace upm;
+using namespace std;
+
+
+AK8975::AK8975(int bus, uint8_t address):
+  m_i2c(bus)
+{
+  m_addr = address;
+  m_xCoeff = 0.0;
+  m_yCoeff = 0.0;
+  m_zCoeff = 0.0;
+
+  mraa_result_t rv;
+  if ( (rv = m_i2c.address(m_addr)) != MRAA_SUCCESS)
+    {
+      cerr << __FUNCTION__ << ": Could not initialize i2c address. " << endl;
+      mraa_result_print(rv);
+      return;
+    }
+}
+
+AK8975::~AK8975()
+{
+}
+
+bool AK8975::init()
+{
+  // we put the device in 'fuse mode', and then read the compensation
+  // coefficients and store them.
+
+  // first, set power down mode
+
+  if (!setMode(CNTL_PWRDWN))
+    {
+      cerr << __FUNCTION__ << ": Unable to set PWRDWN mode" << endl;
+      return false;
+    }
+
+  if (!setMode(CNTL_FUSE_ACCESS))
+    {
+      cerr << __FUNCTION__ << ": Unable to set FUSE mode" << endl;
+      return false;
+    }
+
+  // Read each byte and store
+  m_xCoeff = (float)m_i2c.readReg(REG_ASAX);
+  m_yCoeff = (float)m_i2c.readReg(REG_ASAY);
+  m_zCoeff = (float)m_i2c.readReg(REG_ASAZ);
+
+  // now, place back in power down mode
+  if (!setMode(CNTL_PWRDWN))
+    {
+      cerr << __FUNCTION__ << ": Unable to reset PWRDWN mode" << endl;
+      return false;
+    }
+
+  return true;
+}
+
+bool AK8975::setMode(CNTL_MODES_T mode)
+{
+  mraa_result_t rv;
+  if ((rv = m_i2c.writeReg(REG_CNTL, mode)) != MRAA_SUCCESS)
+    {
+      cerr << __FUNCTION__ << ": failed:" << endl;
+      mraa_result_print(rv);
+      return false;
+    } 
+
+  // sleep at least 100us for for mode transition to complete
+  usleep(150);
+
+  return true;
+}
+
+bool AK8975::isReady()
+{
+  uint8_t rdy = m_i2c.readReg(REG_ST1);
+  
+  if (rdy & ST1_DRDY)
+    return true;
+
+  return false;
+}
+
+bool AK8975::waitforDeviceReady()
+{
+  const int maxRetries = 20;
+
+  int retries = 0;
+
+  while (retries < maxRetries)
+    {
+      if (isReady())
+        return true;
+
+      usleep(5000);
+      retries++;
+    }
+  
+  cerr << __FUNCTION__ << ": timeout waiting for device to become ready"
+       << endl;
+
+  return false;
+}
+
+bool AK8975::update(bool selfTest)
+{
+  // this flag (selfTest) is used so that we can read values without
+  // specifically taking a measurement.  For example, selfTest will
+  // pass true to this method so that the test results aren't
+  // overwritten by a measurement.
+  if (!selfTest)
+    {
+      // First set measurement mode (take a measurement)
+      if (!setMode(CNTL_MEASURE))
+        {
+          cerr << __FUNCTION__ << ": Unable to set MEASURE mode" << endl;
+          return false;
+        }
+    }
+
+  if (!waitforDeviceReady())
+    return false;
+
+  // hope it worked.  Now read out the values and store them (uncompensated)
+  uint8_t data[6];
+  m_i2c.readBytesReg(REG_HXL, data, 6);
+
+  int16_t x, y, z;
+  x = ( (data[1] << 8) | data[0] );
+  y = ( (data[3] << 8) | data[2] );
+  z = ( (data[5] << 8) | data[4] );
+
+  m_xData = float(x);
+  m_yData = float(y);
+  m_zData = float(z);
+
+  return true;
+}
+
+bool AK8975::selfTest()
+{
+  mraa_result_t rv;
+
+  // set power down first
+  if (!setMode(CNTL_PWRDWN))
+    {
+      cerr << __FUNCTION__ << ": Unable to set PWRDWN mode" << endl;
+      return false;
+    }
+
+  // enable self test bit
+  if ((rv = m_i2c.writeReg(REG_ASTC, ASTC_SELF)) != MRAA_SUCCESS)
+    {
+      cerr << __FUNCTION__ << ": failed to enable self test:" << endl;
+      mraa_result_print(rv);
+      return false;
+    } 
+  
+  // now set self test mode
+  if (!setMode(CNTL_SELFTEST))
+    {
+      cerr << __FUNCTION__ << ": Unable to set SELFTEST mode" << endl;
+      return false;
+    }
+  
+  // now update current data (without enabling a measurement)
+  update(true);
+  
+  // Now, reset self test register
+  uint8_t reg = m_i2c.readReg(REG_ASTC);
+  reg &= ~ASTC_SELF;
+  if ((rv = m_i2c.writeReg(REG_ASTC, reg)) != MRAA_SUCCESS)
+    {
+      cerr << __FUNCTION__ << ": failed to disable self test:" << endl;
+      mraa_result_print(rv);
+      return false;
+    } 
+
+  // after self-test measurement, device transitions to power down mode
+  return true;
+}
+
+float AK8975::adjustValue(float value, float adj)
+{
+  // apply the proper compensation to value.  This equation is taken
+  // from the AK8975 datasheet, section 8.3.11
+
+  return ( value * ((((adj - 128.0) * 0.5) / 128.0) + 1.0) );
+} 
+
+void AK8975::getMagnetometer(float *x, float *y, float *z)
+{
+  if (x)
+    *x = adjustValue(m_xData, m_xCoeff);
+  if (y)
+    *y = adjustValue(m_yData, m_yCoeff);
+  if (z)
+    *z = adjustValue(m_zData, m_zCoeff);
+}
+