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/*
* 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 <stdexcept>
#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 rv;
if ( (rv = m_i2c.address(m_addr)) != mraa::SUCCESS)
{
throw std::runtime_error(std::string(__FUNCTION__) +
": I2c.address() failed");
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))
{
throw std::runtime_error(std::string(__FUNCTION__) +
": Unable to set PWRDWN mode");
return false;
}
if (!setMode(CNTL_FUSE_ACCESS))
{
throw std::runtime_error(std::string(__FUNCTION__) +
": Unable to set FUSE mode");
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))
{
throw std::runtime_error(std::string(__FUNCTION__) +
": Unable to set reset PWRDWN mode");
return false;
}
return true;
}
bool AK8975::setMode(CNTL_MODES_T mode)
{
mraa::Result rv;
if ((rv = m_i2c.writeReg(REG_CNTL, mode)) != mraa::SUCCESS)
{
throw std::runtime_error(std::string(__FUNCTION__) +
": I2c.writeReg() failed");
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++;
}
throw std::runtime_error(std::string(__FUNCTION__) +
": timeout waiting for device to become ready");
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))
{
throw std::runtime_error(std::string(__FUNCTION__) +
": Unable to set MEASURE mode");
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 rv;
// set power down first
if (!setMode(CNTL_PWRDWN))
{
throw std::runtime_error(std::string(__FUNCTION__) +
": Unable to set PWRDWN mode");
return false;
}
// enable self test bit
if ((rv = m_i2c.writeReg(REG_ASTC, ASTC_SELF)) != mraa::SUCCESS)
{
throw std::runtime_error(std::string(__FUNCTION__) +
": failed to enable self test");
return false;
}
// now set self test mode
if (!setMode(CNTL_SELFTEST))
{
throw std::runtime_error(std::string(__FUNCTION__) +
": Unable to set SELFTEST mode");
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)
{
throw std::runtime_error(std::string(__FUNCTION__) +
": failed to disable self test");
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);
}
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