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/*
* Copyright © 2012 Keith Packard <keithp@keithp.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; version 2 of the License.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
*/
#ifndef _AO_SAMPLE_H_
#define _AO_SAMPLE_H_
#include <ao_data.h>
/*
* ao_sample.c
*/
/*
* Barometer calibration
*
* We directly sample the barometer. The specs say:
*
* Pressure range: 15-115 kPa
* Voltage at 115kPa: 2.82
* Output scale: 27mV/kPa
*
* If we want to detect launch with the barometer, we need
* a large enough bump to not be fooled by noise. At typical
* launch elevations (0-2000m), a 200Pa pressure change cooresponds
* to about a 20m elevation change. This is 5.4mV, or about 3LSB.
* As all of our calculations are done in 16 bits, we'll actually see a change
* of 16 times this though
*
* 27 mV/kPa * 32767 / 3300 counts/mV = 268.1 counts/kPa
*/
/* Accelerometer calibration
*
* We're sampling the accelerometer through a resistor divider which
* consists of 5k and 10k resistors. This multiplies the values by 2/3.
* That goes into the cc1111 A/D converter, which is running at 11 bits
* of precision with the bits in the MSB of the 16 bit value. Only positive
* values are used, so values should range from 0-32752 for 0-3.3V. The
* specs say we should see 40mV/g (uncalibrated), multiply by 2/3 for what
* the A/D converter sees (26.67 mV/g). We should see 32752/3300 counts/mV,
* for a final computation of:
*
* 26.67 mV/g * 32767/3300 counts/mV = 264.8 counts/g
*
* Zero g was measured at 16000 (we would expect 16384).
* Note that this value is only require to tell if the
* rocket is standing upright. Once that is determined,
* the value of the accelerometer is averaged for 100 samples
* to find the resting accelerometer value, which is used
* for all further flight computations
*/
#define GRAVITY 9.80665
/*
* Above this height, the baro sensor doesn't work
*/
#define AO_MAX_BARO_HEIGHT 12000
/*
* Above this speed, baro measurements are unreliable
*/
#define AO_MAX_BARO_SPEED 200
#define ACCEL_NOSE_UP (ao_accel_2g >> 2)
/*
* Speed and acceleration are scaled by 16 to provide a bit more
* resolution while still having reasonable range. Note that this
* limits speed to 2047m/s (around mach 6) and acceleration to
* 2047m/s² (over 200g)
*/
#define AO_M_TO_HEIGHT(m) ((int16_t) (m))
#define AO_MS_TO_SPEED(ms) ((int16_t) ((ms) * 16))
#define AO_MSS_TO_ACCEL(mss) ((int16_t) ((mss) * 16))
extern __pdata uint16_t ao_sample_tick; /* time of last data */
extern __pdata pres_t ao_sample_pres; /* most recent pressure sensor reading */
extern __pdata alt_t ao_sample_alt; /* MSL of ao_sample_pres */
extern __pdata alt_t ao_sample_height; /* AGL of ao_sample_pres */
extern __data uint8_t ao_sample_adc; /* Ring position of last processed sample */
extern __data uint8_t ao_sample_data; /* Ring position of last processed sample */
#if HAS_ACCEL
extern __pdata accel_t ao_sample_accel; /* most recent accel sensor reading */
#endif
extern __pdata pres_t ao_ground_pres; /* startup pressure */
extern __pdata alt_t ao_ground_height; /* MSL of ao_ground_pres */
#if HAS_ACCEL
extern __pdata accel_t ao_ground_accel; /* startup acceleration */
extern __pdata accel_t ao_accel_2g; /* factory accel calibration */
extern __pdata int32_t ao_accel_scale; /* sensor to m/s² conversion */
#endif
void ao_sample_init(void);
/* returns FALSE in preflight mode, TRUE in flight mode */
uint8_t ao_sample(void);
/*
* ao_kalman.c
*/
#define to_fix16(x) ((int16_t) ((x) * 65536.0 + 0.5))
#define to_fix32(x) ((int32_t) ((x) * 65536.0 + 0.5))
#define from_fix(x) ((x) >> 16)
extern __pdata int16_t ao_height; /* meters */
extern __pdata int16_t ao_speed; /* m/s * 16 */
extern __pdata int16_t ao_accel; /* m/s² * 16 */
extern __pdata int16_t ao_max_height; /* max of ao_height */
extern __pdata int16_t ao_avg_height; /* running average of height */
extern __pdata int16_t ao_error_h;
extern __pdata int16_t ao_error_h_sq_avg;
#if HAS_ACCEL
extern __pdata int16_t ao_error_a;
#endif
void ao_kalman(void);
#endif /* _AO_SAMPLE_H_ */
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