Subversion Repositories FlightCtrl

/*********************************************************************************/
/* Attitude sense system (processing of gyro, accelerometer and altimeter data)  */
/*********************************************************************************/

#ifndef _ATTITUDE_H
#define _ATTITUDE_H

#include <inttypes.h>

#include "analog.h"

// For debugging only.
#include "uart0.h"

/*
 * If you have no acc. sensor or do not want to use it, remove this define. This will cause the
 * acc. sensor to be ignored at attitude calibration.
 */
#define ATTITUDE_USE_ACC_SENSORS yes

/*
 * The frequency at which numerical integration takes place. 488 in original code.
 */
#define INTEGRATION_FREQUENCY 488

/*
 * Gyro readings are divided by this before being used in attitude control. This will scale them
 * to match the scale of the stick control etc. variables. This is just a rough non-precision
 * scaling - the below definitions make precise conversion factors.
 * Will be about 4 for InvenSense, 8 for FC1.3 and 8 for ADXRS610.
 * The number 1250 is derived from the original code: It has about 225000 = 1250 * 180 for 180 degrees.
 */
#define HIRES_GYRO_INTEGRATION_FACTOR 1
// (int)((GYRO_RATE_FACTOR_PITCHROLL * INTEGRATION_FREQUENCY * GYRO_PITCHROLL_CORRECTION) / 1250)

/*
 * Constant for deriving an attitude angle from acceleration measurement.
 *
 * The value is derived from the datasheet of the ACC sensor where 5g are scaled to VRef.
 * 1g is (3V * 1024) / (5 * 3V) = 205 counts. The ADC ISR sums 2 acc. samples to each
 * [pitch/roll]AxisAcc and thus reads about acc = 410 counts / g.
 * We approximate a small pitch/roll angle v by assuming that the copter does not accelerate:
 * In this explanation it is assumed that the ADC values are 0 based, and gravity is included.
 * The sine of v is the far side / the hypothenusis:
 * sin v = acc / sqrt(acc^2 + acc_z^2)
 * Using that v is a small angle, and the near side is about equal to the the hypothenusis:
 * sin v ~= acc / acc_z
 * Assuming that the helicopter is hovering at small pitch and roll angles, acc_z is about 410,
 * and sin v ~= v (small angles, in radians):
 * sin v ~= acc / 410
 * v / 57.3 ~= acc / 410
 * v ~= acc * 57.3 / 410
 * acc / v ~= 410 / 57.3 ~= 7, that is: There are about 7 counts per degree.
 *
 * Summary: DEG_ACC_FACTOR = (2 * 1024 * [sensitivity of acc. meter in V/g]) / (3V * 57.3)
 */
#define DEG_ACC_FACTOR 7

/*
 * Growth of the integral per degree:
 * The hiResXXXX value per deg / s * INTEGRATION_FREQUENCY samples / sec * correction / a number divided by
 * HIRES_GYRO_INTEGRATION_FACTOR (why???) before integration.
 * The value of this expression should be about 1250 (by setting HIRES_GYRO_INTEGRATION_FACTOR to something suitable).
 */
#define GYRO_DEG_FACTOR_PITCHROLL (GYRO_RATE_FACTOR_PITCHROLL * INTEGRATION_FREQUENCY * GYRO_PITCHROLL_CORRECTION / HIRES_GYRO_INTEGRATION_FACTOR)
#define GYRO_DEG_FACTOR_YAW (GYRO_RATE_FACTOR_YAW * INTEGRATION_FREQUENCY * GYRO_YAW_CORRECTION)

/*
 * This is ([gyro integral value] / degree) / (degree / acc. sensor value) = gyro integral value / acc.sensor value
 * = the factor an acc. sensor should be multiplied by to get the gyro integral
 * value for the same (small) angle.
 * The value is about 200.
 */
#define GYRO_ACC_FACTOR ((GYRO_DEG_FACTOR_PITCHROLL) / (DEG_ACC_FACTOR))

#define PITCHROLLOVER180 ((int32_t)GYRO_DEG_FACTOR_PITCHROLL * 180)
#define PITCHROLLOVER360 ((int32_t)GYRO_DEG_FACTOR_PITCHROLL * 360)
#define YAWOVER360       ((int32_t)GYRO_DEG_FACTOR_YAW * 360)

/*
 * Rotation rates
 */
extern int16_t rate_PID[2], rate_ATT[2], yawRate;
extern int16_t differential[3];

/*
 * Attitudes calculated by numerical integration of gyro rates
 */
extern int32_t angle[3];
extern int32_t error[3];

/*
 * Dynamic gyro offsets. These are signed values that are subtracted from the gyro measurements,
 * to help canceling out drift and vibration noise effects. The dynamic offsets themselves
 * can be updated in flight by different ways, for example:
 * - Just taking them from parameters, so the pilot can trim manually in a PC or mobile tool
 * - Summing up how much acc. meter correction was done to the gyro integrals over the last n
 *   integration, and then adding the sum / n to the dynamic offset
 * - Detect which way the pilot pulls the stick to keep the copter steady, and correct by that
 * - Invent your own...
 */
extern int16_t dynamicOffset[2], dynamicOffsetYaw;

/*
 * For NaviCtrl use.
 */
extern int16_t averageAcc[2], averageAccCount;

/*
 * Re-init flight attitude, setting all angles to 0 (or to whatever can be derived from acc. sensor).
 * To be called when the pilot commands gyro calibration (eg. by moving the left stick up-left or up-right).
 */
void attitude_setNeutral(void);

/*
 * Experiment.
 */
// void attitude_startDynamicCalibration(void);
// void attitude_continueDynamicCalibration(void);

int32_t getAngleEstimateFromAcc(uint8_t axis);

/*
 * Main routine, called from the flight loop.
 */
void calculateFlightAttitude(void);
#endif //_ATTITUDE_H