ardupilot/libraries/AP_InertialSensor/AP_InertialSensor_Backend.cpp

#include <AP_HAL/AP_HAL.h>
#include "AP_InertialSensor.h"
#include "AP_InertialSensor_Backend.h"
#include <DataFlash/DataFlash.h>
#if AP_MODULE_SUPPORTED
#include <AP_Module/AP_Module.h>
#include <stdio.h>
#endif

#define SENSOR_RATE_DEBUG 0

const extern AP_HAL::HAL& hal;

AP_InertialSensor_Backend::AP_InertialSensor_Backend(AP_InertialSensor &imu) :
    _imu(imu)
{
    _sem = hal.util->new_semaphore();
}

/*
  notify of a FIFO reset so we don't use bad data to update observed sensor rate
 */
void AP_InertialSensor_Backend::notify_accel_fifo_reset(uint8_t instance)
{
    _imu._sample_accel_count[instance] = 0;
    _imu._sample_accel_start_us[instance] = 0;    
}

/*
  notify of a FIFO reset so we don't use bad data to update observed sensor rate
 */
void AP_InertialSensor_Backend::notify_gyro_fifo_reset(uint8_t instance)
{
    _imu._sample_gyro_count[instance] = 0;
    _imu._sample_gyro_start_us[instance] = 0;
}

// set the amount of oversamping a accel is doing
void AP_InertialSensor_Backend::_set_accel_oversampling(uint8_t instance, uint8_t n)
{
    _imu._accel_over_sampling[instance] = n;
}

// set the amount of oversamping a gyro is doing
void AP_InertialSensor_Backend::_set_gyro_oversampling(uint8_t instance, uint8_t n)
{
    _imu._gyro_over_sampling[instance] = n;
}

/*
  update the sensor rate for FIFO sensors

  FIFO sensors produce samples at a fixed rate, but the clock in the
  sensor may vary slightly from the system clock. This slowly adjusts
  the rate to the observed rate
*/
void AP_InertialSensor_Backend::_update_sensor_rate(uint16_t &count, uint32_t &start_us, float &rate_hz)
{
    uint32_t now = AP_HAL::micros();
    if (start_us == 0) {
        count = 0;
        start_us = now;
    } else {
        count++;
        if (now - start_us > 1000000UL) {
            float observed_rate_hz = count * 1.0e6 / (now - start_us);
#if SENSOR_RATE_DEBUG
            printf("RATE: %.1f should be %.1f\n", observed_rate_hz, rate_hz);
#endif
            float filter_constant = 0.98;
            float upper_limit = 1.05;
            float lower_limit = 0.95;
            if (AP_HAL::millis() < 30000) {
                // converge quickly for first 30s, then more slowly
                filter_constant = 0.8;
                upper_limit = 2.0;
                lower_limit = 0.5;
            }
            observed_rate_hz = constrain_float(observed_rate_hz, rate_hz*lower_limit, rate_hz*upper_limit);
            rate_hz = filter_constant * rate_hz + (1-filter_constant) * observed_rate_hz;
            count = 0;
            start_us = now;
        }
    }
}

void AP_InertialSensor_Backend::_rotate_and_correct_accel(uint8_t instance, Vector3f &accel) 
{
    /*
      accel calibration is always done in sensor frame with this
      version of the code. That means we apply the rotation after the
      offsets and scaling.
     */

    // rotate for sensor orientation
    accel.rotate(_imu._accel_orientation[instance]);
    
    // apply offsets
    accel -= _imu._accel_offset[instance];

    // apply scaling
    const Vector3f &accel_scale = _imu._accel_scale[instance].get();
    accel.x *= accel_scale.x;
    accel.y *= accel_scale.y;
    accel.z *= accel_scale.z;

    // rotate to body frame
    accel.rotate(_imu._board_orientation);
}

void AP_InertialSensor_Backend::_rotate_and_correct_gyro(uint8_t instance, Vector3f &gyro) 
{
    // rotate for sensor orientation
    gyro.rotate(_imu._gyro_orientation[instance]);
    
    // gyro calibration is always assumed to have been done in sensor frame
    gyro -= _imu._gyro_offset[instance];

    gyro.rotate(_imu._board_orientation);
}

/*
  rotate gyro vector and add the gyro offset
 */
void AP_InertialSensor_Backend::_publish_gyro(uint8_t instance, const Vector3f &gyro)
{
    _imu._gyro[instance] = gyro;
    _imu._gyro_healthy[instance] = true;

    // publish delta angle
    _imu._delta_angle[instance] = _imu._delta_angle_acc[instance];
    _imu._delta_angle_dt[instance] = _imu._delta_angle_acc_dt[instance];
    _imu._delta_angle_valid[instance] = true;
}

void AP_InertialSensor_Backend::_notify_new_gyro_raw_sample(uint8_t instance,
                                                            const Vector3f &gyro,
                                                            uint64_t sample_us)
{
    float dt;

    _update_sensor_rate(_imu._sample_gyro_count[instance], _imu._sample_gyro_start_us[instance],
                        _imu._gyro_raw_sample_rates[instance]);

    /*
      we have two classes of sensors. FIFO based sensors produce data
      at a very predictable overall rate, but the data comes in
      bunches, so we use the provided sample rate for deltaT. Non-FIFO
      sensors don't bunch up samples, but also tend to vary in actual
      rate, so we use the provided sample_us to get the deltaT. The
      difference between the two is whether sample_us is provided.
     */
    if (sample_us != 0 && _imu._gyro_last_sample_us[instance] != 0) {
        dt = (sample_us - _imu._gyro_last_sample_us[instance]) * 1.0e-6;
    } else {
        // don't accept below 100Hz
        if (_imu._gyro_raw_sample_rates[instance] < 100) {
            return;
        }

        dt = 1.0f / _imu._gyro_raw_sample_rates[instance];
    }
    _imu._gyro_last_sample_us[instance] = sample_us;

#if AP_MODULE_SUPPORTED
    // call gyro_sample hook if any
    AP_Module::call_hook_gyro_sample(instance, dt, gyro);
#endif

    // push gyros if optical flow present
    if (hal.opticalflow)
        hal.opticalflow->push_gyro(gyro.x, gyro.y, dt);
    
    // compute delta angle
    Vector3f delta_angle = (gyro + _imu._last_raw_gyro[instance]) * 0.5f * dt;

    // compute coning correction
    // see page 26 of:
    // Tian et al (2010) Three-loop Integration of GPS and Strapdown INS with Coning and Sculling Compensation
    // Available: http://www.sage.unsw.edu.au/snap/publications/tian_etal2010b.pdf
    // see also examples/coning.py
    Vector3f delta_coning = (_imu._delta_angle_acc[instance] +
                             _imu._last_delta_angle[instance] * (1.0f / 6.0f));
    delta_coning = delta_coning % delta_angle;
    delta_coning *= 0.5f;

    if (_sem->take(HAL_SEMAPHORE_BLOCK_FOREVER)) {
        // integrate delta angle accumulator
        // the angles and coning corrections are accumulated separately in the
        // referenced paper, but in simulation little difference was found between
        // integrating together and integrating separately (see examples/coning.py)
        _imu._delta_angle_acc[instance] += delta_angle + delta_coning;
        _imu._delta_angle_acc_dt[instance] += dt;

        // save previous delta angle for coning correction
        _imu._last_delta_angle[instance] = delta_angle;
        _imu._last_raw_gyro[instance] = gyro;

        _imu._gyro_filtered[instance] = _imu._gyro_filter[instance].apply(gyro);
        if (_imu._gyro_filtered[instance].is_nan() || _imu._gyro_filtered[instance].is_inf()) {
            _imu._gyro_filter[instance].reset();
        }
        _imu._new_gyro_data[instance] = true;
        _sem->give();
    }

    log_gyro_raw(instance, sample_us, gyro);
}

void AP_InertialSensor_Backend::log_gyro_raw(uint8_t instance, const uint64_t sample_us, const Vector3f &gyro)
{
    DataFlash_Class *dataflash = DataFlash_Class::instance();
    if (dataflash == nullptr) {
        // should not have been called
        return;
    }
    if (should_log_imu_raw()) {
        uint64_t now = AP_HAL::micros64();
        struct log_GYRO pkt = {
            LOG_PACKET_HEADER_INIT((uint8_t)(LOG_GYR1_MSG+instance)),
            time_us   : now,
            sample_us : sample_us?sample_us:now,
            GyrX      : gyro.x,
            GyrY      : gyro.y,
            GyrZ      : gyro.z
        };
        dataflash->WriteBlock(&pkt, sizeof(pkt));
    } else {
        _imu.batchsampler.sample(instance, AP_InertialSensor::IMU_SENSOR_TYPE_GYRO, sample_us, gyro);
    }
}

/*
  rotate accel vector, scale and add the accel offset
 */
void AP_InertialSensor_Backend::_publish_accel(uint8_t instance, const Vector3f &accel)
{
    _imu._accel[instance] = accel;
    _imu._accel_healthy[instance] = true;

    // publish delta velocity
    _imu._delta_velocity[instance] = _imu._delta_velocity_acc[instance];
    _imu._delta_velocity_dt[instance] = _imu._delta_velocity_acc_dt[instance];
    _imu._delta_velocity_valid[instance] = true;


    if (_imu._accel_calibrator != nullptr && _imu._accel_calibrator[instance].get_status() == ACCEL_CAL_COLLECTING_SAMPLE) {
        Vector3f cal_sample = _imu._delta_velocity[instance];

        //remove rotation
        cal_sample.rotate_inverse(_imu._board_orientation);

        // remove scale factors
        const Vector3f &accel_scale = _imu._accel_scale[instance].get();
        cal_sample.x /= accel_scale.x;
        cal_sample.y /= accel_scale.y;
        cal_sample.z /= accel_scale.z;
        
        //remove offsets
        cal_sample += _imu._accel_offset[instance].get() * _imu._delta_velocity_dt[instance] ;

        _imu._accel_calibrator[instance].new_sample(cal_sample, _imu._delta_velocity_dt[instance]);
    }
}

void AP_InertialSensor_Backend::_notify_new_accel_raw_sample(uint8_t instance,
                                                             const Vector3f &accel,
                                                             uint64_t sample_us,
                                                             bool fsync_set)
{
    float dt;

    _update_sensor_rate(_imu._sample_accel_count[instance], _imu._sample_accel_start_us[instance],
                        _imu._accel_raw_sample_rates[instance]);

    /*
      we have two classes of sensors. FIFO based sensors produce data
      at a very predictable overall rate, but the data comes in
      bunches, so we use the provided sample rate for deltaT. Non-FIFO
      sensors don't bunch up samples, but also tend to vary in actual
      rate, so we use the provided sample_us to get the deltaT. The
      difference between the two is whether sample_us is provided.
     */
    if (sample_us != 0 && _imu._accel_last_sample_us[instance] != 0) {
        dt = (sample_us - _imu._accel_last_sample_us[instance]) * 1.0e-6;
    } else {
        // don't accept below 100Hz
        if (_imu._accel_raw_sample_rates[instance] < 100) {
            return;
        }

        dt = 1.0f / _imu._accel_raw_sample_rates[instance];
    }
    _imu._accel_last_sample_us[instance] = sample_us;

#if AP_MODULE_SUPPORTED
    // call accel_sample hook if any
    AP_Module::call_hook_accel_sample(instance, dt, accel, fsync_set);
#endif    
    
    _imu.calc_vibration_and_clipping(instance, accel, dt);

    if (_sem->take(HAL_SEMAPHORE_BLOCK_FOREVER)) {
        // delta velocity
        _imu._delta_velocity_acc[instance] += accel * dt;
        _imu._delta_velocity_acc_dt[instance] += dt;

        _imu._accel_filtered[instance] = _imu._accel_filter[instance].apply(accel);
        if (_imu._accel_filtered[instance].is_nan() || _imu._accel_filtered[instance].is_inf()) {
            _imu._accel_filter[instance].reset();
        }

        _imu.set_accel_peak_hold(instance, _imu._accel_filtered[instance]);

        _imu._new_accel_data[instance] = true;
        _sem->give();
    }

    log_accel_raw(instance, sample_us, accel);
}

void AP_InertialSensor_Backend::log_accel_raw(uint8_t instance, const uint64_t sample_us, const Vector3f &accel)
{
    DataFlash_Class *dataflash = DataFlash_Class::instance();
    if (dataflash == nullptr) {
        // should not have been called
        return;
    }
    if (should_log_imu_raw()) {
        uint64_t now = AP_HAL::micros64();
        struct log_ACCEL pkt = {
            LOG_PACKET_HEADER_INIT((uint8_t)(LOG_ACC1_MSG+instance)),
            time_us   : now,
            sample_us : sample_us?sample_us:now,
            AccX      : accel.x,
            AccY      : accel.y,
            AccZ      : accel.z
        };
        dataflash->WriteBlock(&pkt, sizeof(pkt));
    } else {
        _imu.batchsampler.sample(instance, AP_InertialSensor::IMU_SENSOR_TYPE_ACCEL, sample_us, accel);
    }
}

void AP_InertialSensor_Backend::_set_accel_max_abs_offset(uint8_t instance,
                                                          float max_offset)
{
    _imu._accel_max_abs_offsets[instance] = max_offset;
}

// set accelerometer error_count
void AP_InertialSensor_Backend::_set_accel_error_count(uint8_t instance, uint32_t error_count)
{
    _imu._accel_error_count[instance] = error_count;
}

// set gyro error_count
void AP_InertialSensor_Backend::_set_gyro_error_count(uint8_t instance, uint32_t error_count)
{
    _imu._gyro_error_count[instance] = error_count;
}

// increment accelerometer error_count
void AP_InertialSensor_Backend::_inc_accel_error_count(uint8_t instance)
{
    _imu._accel_error_count[instance]++;
}

// increment gyro error_count
void AP_InertialSensor_Backend::_inc_gyro_error_count(uint8_t instance)
{
    _imu._gyro_error_count[instance]++;
}

// return the requested sample rate in Hz
uint16_t AP_InertialSensor_Backend::get_sample_rate_hz(void) const
{
    // enum can be directly cast to Hz
    return (uint16_t)_imu._sample_rate;
}

/*
  publish a temperature value for an instance
 */
void AP_InertialSensor_Backend::_publish_temperature(uint8_t instance, float temperature)
{
    _imu._temperature[instance] = temperature;

    /* give the temperature to the control loop in order to keep it constant*/
    if (instance == 0) {
        hal.util->set_imu_temp(temperature);
    }
}

/*
  common gyro update function for all backends
 */
void AP_InertialSensor_Backend::update_gyro(uint8_t instance)
{    
    if (!_sem->take(HAL_SEMAPHORE_BLOCK_FOREVER)) {
        return;
    }

    if (_imu._new_gyro_data[instance]) {
        _publish_gyro(instance, _imu._gyro_filtered[instance]);
        _imu._new_gyro_data[instance] = false;
    }

    // possibly update filter frequency
    if (_last_gyro_filter_hz[instance] != _gyro_filter_cutoff()) {
        _imu._gyro_filter[instance].set_cutoff_frequency(_gyro_raw_sample_rate(instance), _gyro_filter_cutoff());
        _last_gyro_filter_hz[instance] = _gyro_filter_cutoff();
    }

    _sem->give();
}

/*
  common accel update function for all backends
 */
void AP_InertialSensor_Backend::update_accel(uint8_t instance)
{    
    if (!_sem->take(HAL_SEMAPHORE_BLOCK_FOREVER)) {
        return;
    }

    if (_imu._new_accel_data[instance]) {
        _publish_accel(instance, _imu._accel_filtered[instance]);
        _imu._new_accel_data[instance] = false;
    }
    
    // possibly update filter frequency
    if (_last_accel_filter_hz[instance] != _accel_filter_cutoff()) {
        _imu._accel_filter[instance].set_cutoff_frequency(_accel_raw_sample_rate(instance), _accel_filter_cutoff());
        _last_accel_filter_hz[instance] = _accel_filter_cutoff();
    }

    _sem->give();
}

bool AP_InertialSensor_Backend::should_log_imu_raw() const
{
    if (_imu._log_raw_bit == (uint32_t)-1) {
        // tracker does not set a bit
        return false;
    }
    const DataFlash_Class *instance = DataFlash_Class::instance();
    if (instance == nullptr) {
        return false;
    }
    if (!instance->should_log(_imu._log_raw_bit)) {
        return false;
    }
    return true;
}