GY50.cpp

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/*
    L3G4200D implementation based on code by:
    * http://bildr.org/2011/06/l3g4200d-arduino/
    * http://www.pieter-jan.com/node/7
    * https://github.com/sparkfun/Tri-Axis_Gyro_Breakout-L3G4200D
*/
#include "GY50.hpp"
#include "../../../utilities/Utilities.hpp"
 
namespace
{
const uint8_t kGyroAddress      = 105;
const auto kMeasurementInterval = 100;
const float kGyroSensitivity    = 0.07F;
const int kGyroThreshold        = 12; // Smaller changes are to be ignored
} // namespace
 
using namespace smartcarlib::utils;
using namespace smartcarlib::constants::gy50;
 
GY50::GY50(Runtime& runtime, int offset, unsigned long samplingInterval)
    : kOffset{ offset }
    , kSamplingInterval{ samplingInterval }
    , mRuntime{ runtime }
{
}
 
int GY50::getHeading()
{
    // Get the reading from (-180,180) to [0, 360) scale
    static constexpr auto kFullScaleDegrees = 360;
    auto normalizedReading = static_cast<int>(mAngularDisplacement) % kFullScaleDegrees;
 
    return normalizedReading < 0 ? normalizedReading + kFullScaleDegrees : normalizedReading;
}
 
void GY50::update()
{
    unsigned long currentTime = mRuntime.currentTimeMillis();
    unsigned long interval    = currentTime - mPreviousSample;
    if (interval <= kSamplingInterval)
    {
        return; // Not the time to read yet
    }
 
    int drift = kOffset - getAngularVelocity();
 
    if (getAbsolute(drift) > kGyroThreshold)
    {
        float gyroRate                               = static_cast<float>(drift) * kGyroSensitivity;
        static constexpr auto kGyroscopeReadingScale = 1000.0F;
        mAngularDisplacement += gyroRate / (kGyroscopeReadingScale / static_cast<float>(interval));
    }
    mPreviousSample = currentTime;
}
 
void GY50::attach()
{
    if (mAttached)
    {
        return;
    }
 
    mRuntime.i2cInit();
    // Enable z and turn off power down
    static constexpr uint8_t kControlRegister1 = 0x20;
    writeL3G4200DRegister(kControlRegister1, 0b00001100); // NOLINT(readability-magic-numbers)
    // If you'd like to adjust/use the HPF, you can edit the line below to configure CTRL_REG2
    static constexpr uint8_t kControlRegister2 = 0x21;
    writeL3G4200DRegister(kControlRegister2, 0b00000000); // NOLINT(readability-magic-numbers)
    // Configure CTRL_REG3 to generate data ready interrupt on INT2
    // No interrupts used on INT1, if you'd like to configure INT1
    // or INT2 otherwise, consult the datasheet
    static constexpr uint8_t kControlRegister3 = 0x22;
    writeL3G4200DRegister(kControlRegister3, 0b00001000); // NOLINT(readability-magic-numbers)
    // CTRL_REG4 controls the full-scale range, among other things
    static constexpr uint8_t kControlRegister4 = 0x23;
    writeL3G4200DRegister(kControlRegister4, 0b00110000); // NOLINT(readability-magic-numbers)
    // CTRL_REG5 controls high-pass filtering of outputs, use it if you'd like
    static constexpr uint8_t kControlRegister5 = 0x24;
    writeL3G4200DRegister(kControlRegister5, 0b00000000); // NOLINT(readability-magic-numbers)
 
    mAttached = true;
}
 
int GY50::getOffset(int measurements)
{
    if (measurements <= 0)
    {
        return kError;
    }
 
    long sum = 0;
    for (auto i = 0; i < measurements; i++)
    {
        sum += getAngularVelocity();
        mRuntime.delayMillis(kMeasurementInterval);
    }
 
    return static_cast<int>(sum / measurements);
}
 
int GY50::getAngularVelocity()
{
    attach();
 
    static const uint8_t zAxisFirstByteRegister  = 0x2D;
    static const uint8_t zAxisSecondByteRegister = 0x2C;
 
    auto firstByte  = readL3G4200DRegister(zAxisFirstByteRegister);
    auto secondByte = readL3G4200DRegister(zAxisSecondByteRegister);
 
    static constexpr auto kBitsInByte = 8;
 
    return static_cast<int16_t>((firstByte << kBitsInByte) | secondByte);
}
 
int GY50::readL3G4200DRegister(uint8_t registerAddress)
{
    mRuntime.i2cBeginTransmission(kGyroAddress);
    mRuntime.i2cWrite(registerAddress);
    mRuntime.i2cEndTransmission();
    mRuntime.i2cRequestFrom(kGyroAddress, 1);
 
    return mRuntime.i2cAvailable() != 0 ? mRuntime.i2cRead() : 0;
}
 
void GY50::writeL3G4200DRegister(uint8_t registerAddress, uint8_t value)
{
    mRuntime.i2cBeginTransmission(kGyroAddress);
    mRuntime.i2cWrite(registerAddress);
    mRuntime.i2cWrite(value);
    mRuntime.i2cEndTransmission();
}