2 * Copyright © 2009 Keith Packard <keithp@keithp.com>
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; version 2 of the License.
8 * This program is distributed in the hope that it will be useful, but
9 * WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
11 * General Public License for more details.
13 * You should have received a copy of the GNU General Public License along
14 * with this program; if not, write to the Free Software Foundation, Inc.,
15 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
18 #ifndef AO_FLIGHT_TEST
22 /* Main flight thread. */
24 __pdata enum ao_flight_state ao_flight_state; /* current flight state */
25 __pdata uint16_t ao_flight_tick; /* time of last data */
26 __pdata uint16_t ao_flight_prev_tick; /* time of previous data */
27 __pdata int16_t ao_flight_accel; /* filtered acceleration */
28 __pdata int16_t ao_flight_pres; /* filtered pressure */
29 __pdata int16_t ao_ground_pres; /* startup pressure */
30 __pdata int16_t ao_ground_accel; /* startup acceleration */
31 __pdata int16_t ao_min_pres; /* minimum recorded pressure */
32 __pdata uint16_t ao_launch_tick; /* time of launch detect */
33 __pdata int16_t ao_main_pres; /* pressure to eject main */
36 * track min/max data over a long interval to detect
39 __pdata uint16_t ao_interval_end;
40 __pdata int16_t ao_interval_cur_min_accel;
41 __pdata int16_t ao_interval_cur_max_accel;
42 __pdata int16_t ao_interval_cur_min_pres;
43 __pdata int16_t ao_interval_cur_max_pres;
44 __pdata int16_t ao_interval_min_accel;
45 __pdata int16_t ao_interval_max_accel;
46 __pdata int16_t ao_interval_min_pres;
47 __pdata int16_t ao_interval_max_pres;
49 __data uint8_t ao_flight_adc;
50 __pdata int16_t ao_raw_accel, ao_raw_accel_prev, ao_raw_pres;
51 __pdata int16_t ao_accel_2g;
53 __xdata uint8_t ao_flight_force_idle;
55 /* Accelerometer calibration
57 * We're sampling the accelerometer through a resistor divider which
58 * consists of 5k and 10k resistors. This multiplies the values by 2/3.
59 * That goes into the cc1111 A/D converter, which is running at 11 bits
60 * of precision with the bits in the MSB of the 16 bit value. Only positive
61 * values are used, so values should range from 0-32752 for 0-3.3V. The
62 * specs say we should see 40mV/g (uncalibrated), multiply by 2/3 for what
63 * the A/D converter sees (26.67 mV/g). We should see 32752/3300 counts/mV,
64 * for a final computation of:
66 * 26.67 mV/g * 32767/3300 counts/mV = 264.8 counts/g
68 * Zero g was measured at 16000 (we would expect 16384).
69 * Note that this value is only require to tell if the
70 * rocket is standing upright. Once that is determined,
71 * the value of the accelerometer is averaged for 100 samples
72 * to find the resting accelerometer value, which is used
73 * for all further flight computations
76 #define GRAVITY 9.80665
77 /* convert m/s to velocity count */
78 #define VEL_MPS_TO_COUNT(mps) (((int32_t) (((mps) / GRAVITY) * (AO_HERTZ/2))) * (int32_t) ao_accel_2g)
80 #define ACCEL_NOSE_UP (ao_accel_2g >> 2)
81 #define ACCEL_BOOST ao_accel_2g
82 #define ACCEL_COAST (ao_accel_2g >> 3)
83 #define ACCEL_INT_LAND (ao_accel_2g >> 3)
84 #define ACCEL_VEL_MACH VEL_MPS_TO_COUNT(200)
85 #define ACCEL_VEL_BOOST VEL_MPS_TO_COUNT(5)
88 * Barometer calibration
90 * We directly sample the barometer. The specs say:
92 * Pressure range: 15-115 kPa
93 * Voltage at 115kPa: 2.82
94 * Output scale: 27mV/kPa
96 * If we want to detect launch with the barometer, we need
97 * a large enough bump to not be fooled by noise. At typical
98 * launch elevations (0-2000m), a 200Pa pressure change cooresponds
99 * to about a 20m elevation change. This is 5.4mV, or about 3LSB.
100 * As all of our calculations are done in 16 bits, we'll actually see a change
101 * of 16 times this though
103 * 27 mV/kPa * 32767 / 3300 counts/mV = 268.1 counts/kPa
107 #define BARO_LAUNCH (BARO_kPa / 5) /* .2kPa, or about 20m */
108 #define BARO_APOGEE (BARO_kPa / 10) /* .1kPa, or about 10m */
109 #define BARO_COAST (BARO_kPa * 5) /* 5kpa, or about 500m */
110 #define BARO_MAIN (BARO_kPa) /* 1kPa, or about 100m */
111 #define BARO_INT_LAND (BARO_kPa / 20) /* .05kPa, or about 5m */
112 #define BARO_LAND (BARO_kPa * 10) /* 10kPa or about 1000m */
114 /* We also have a clock, which can be used to sanity check things in
115 * case of other failures
118 #define BOOST_TICKS_MAX AO_SEC_TO_TICKS(15)
120 /* This value is scaled in a weird way. It's a running total of accelerometer
121 * readings minus the ground accelerometer reading. That means it measures
122 * velocity, and quite accurately too. As it gets updated 100 times a second,
125 __pdata int32_t ao_flight_vel;
126 __pdata int32_t ao_min_vel;
127 __pdata int32_t ao_old_vel;
128 __pdata int16_t ao_old_vel_tick;
129 __xdata int32_t ao_raw_accel_sum, ao_raw_pres_sum;
131 /* Landing is detected by getting constant readings from both pressure and accelerometer
132 * for a fairly long time (AO_INTERVAL_TICKS)
134 #define AO_INTERVAL_TICKS AO_SEC_TO_TICKS(5)
136 #define abs(a) ((a) < 0 ? -(a) : (a))
141 __pdata static uint16_t nsamples = 0;
143 ao_flight_adc = ao_adc_head;
144 ao_raw_accel_prev = 0;
149 ao_sleep(&ao_adc_ring);
150 while (ao_flight_adc != ao_adc_head) {
151 __pdata uint8_t ticks;
152 __pdata int16_t ao_vel_change;
153 ao_flight_prev_tick = ao_flight_tick;
155 /* Capture a sample */
156 ao_raw_accel = ao_adc_ring[ao_flight_adc].accel;
157 ao_raw_pres = ao_adc_ring[ao_flight_adc].pres;
158 ao_flight_tick = ao_adc_ring[ao_flight_adc].tick;
160 ao_flight_accel -= ao_flight_accel >> 4;
161 ao_flight_accel += ao_raw_accel >> 4;
162 ao_flight_pres -= ao_flight_pres >> 4;
163 ao_flight_pres += ao_raw_pres >> 4;
166 * The accelerometer is mounted so that
167 * acceleration yields negative values
168 * while deceleration yields positive values,
169 * so subtract instead of add.
171 ticks = ao_flight_tick - ao_flight_prev_tick;
172 ao_vel_change = ao_ground_accel - (((ao_raw_accel + 1) >> 1) + ((ao_raw_accel_prev + 1) >> 1));
173 ao_raw_accel_prev = ao_raw_accel;
175 /* one is a common interval */
177 ao_flight_vel += (int32_t) ao_vel_change;
179 ao_flight_vel += (int32_t) ao_vel_change * (int32_t) ticks;
181 ao_flight_adc = ao_adc_ring_next(ao_flight_adc);
184 if (ao_flight_pres < ao_min_pres)
185 ao_min_pres = ao_flight_pres;
186 if (ao_flight_vel >= 0) {
187 if (ao_flight_vel < ao_min_vel)
188 ao_min_vel = ao_flight_vel;
190 if (-ao_flight_vel < ao_min_vel)
191 ao_min_vel = -ao_flight_vel;
194 switch (ao_flight_state) {
195 case ao_flight_startup:
199 * Collect 1000 samples of acceleration and pressure
200 * data and average them to find the resting values
202 if (nsamples < 1000) {
203 ao_raw_accel_sum += ao_raw_accel;
204 ao_raw_pres_sum += ao_raw_pres;
208 ao_ground_accel = (ao_raw_accel_sum / nsamples);
209 ao_ground_pres = (ao_raw_pres_sum / nsamples);
210 ao_min_pres = ao_ground_pres;
212 ao_main_pres = ao_altitude_to_pres(ao_pres_to_altitude(ao_ground_pres) + ao_config.main_deploy);
213 ao_accel_2g = ao_config.accel_minus_g - ao_config.accel_plus_g;
216 ao_old_vel = ao_flight_vel;
217 ao_old_vel_tick = ao_flight_tick;
219 /* Go to pad state if the nose is pointing up */
221 if (ao_config.accel_plus_g != 0 &&
222 ao_config.accel_minus_g != 0 &&
223 ao_flight_accel < ao_config.accel_plus_g + ACCEL_NOSE_UP &&
224 !ao_flight_force_idle)
226 /* Disable the USB controller in flight mode
231 /* Turn on telemetry system
234 ao_telemetry_set_interval(AO_TELEMETRY_INTERVAL_PAD);
236 ao_flight_state = ao_flight_pad;
237 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
239 ao_flight_state = ao_flight_idle;
241 /* Turn on packet system in idle mode
243 ao_packet_slave_start();
244 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
246 /* signal successful initialization by turning off the LED */
247 ao_led_off(AO_LED_RED);
253 * Once a second, remove any velocity from
256 if ((int16_t) (ao_flight_tick - ao_old_vel_tick) >= AO_SEC_TO_TICKS(1)) {
257 ao_old_vel_tick = ao_flight_tick;
258 ao_flight_vel -= ao_old_vel;
259 ao_old_vel = ao_flight_vel;
263 * accelerometer: > 2g AND velocity > 5m/s
265 * barometer: > 20m vertical motion
267 * The accelerometer should always detect motion before
268 * the barometer, but we use both to make sure this
269 * transition is detected
271 if ((ao_flight_accel < ao_ground_accel - ACCEL_BOOST &&
272 ao_flight_vel > ACCEL_VEL_BOOST) ||
273 ao_flight_pres < ao_ground_pres - BARO_LAUNCH)
275 ao_flight_state = ao_flight_boost;
276 ao_launch_tick = ao_flight_tick;
278 /* start logging data */
281 /* Increase telemetry rate */
282 ao_telemetry_set_interval(AO_TELEMETRY_INTERVAL_FLIGHT);
284 /* disable RDF beacon */
287 /* Record current GPS position by waking up GPS log tasks */
288 ao_wakeup(&ao_gps_data);
289 ao_wakeup(&ao_gps_tracking_data);
291 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
295 case ao_flight_boost:
299 * accelerometer: start to fall at > 1/4 G
301 * time: boost for more than 15 seconds
303 * Detects motor burn out by the switch from acceleration to
304 * deceleration, or by waiting until the maximum burn duration
305 * (15 seconds) has past.
307 if (ao_flight_accel > ao_ground_accel + ACCEL_COAST ||
308 (int16_t) (ao_flight_tick - ao_launch_tick) > BOOST_TICKS_MAX)
310 ao_flight_state = ao_flight_fast;
311 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
319 * accelerometer: integrated velocity < 200 m/s
321 * barometer: fall at least 500m from max altitude
323 * This extra state is required to avoid mis-detecting
324 * apogee due to mach transitions.
326 * XXX this is essentially a single-detector test
327 * as the 500m altitude change would likely result
328 * in a loss of the rocket. More data on precisely
329 * how big a pressure change the mach transition
330 * generates would be useful here.
332 if (ao_flight_vel < ACCEL_VEL_MACH ||
333 ao_flight_pres > ao_min_pres + BARO_COAST)
335 /* set min velocity to current velocity for
338 ao_min_vel = abs(ao_flight_vel);
339 ao_flight_state = ao_flight_coast;
340 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
343 case ao_flight_coast:
345 /* apogee detect: coast to drogue deploy:
347 * barometer: fall at least 10m
349 * It would be nice to use the accelerometer
350 * to detect apogee as well, but tests have
351 * shown that flights far from vertical would
352 * grossly mis-detect apogee. So, for now,
353 * we'll trust to a single sensor for this test
355 if (ao_flight_pres > ao_min_pres + BARO_APOGEE)
357 /* ignite the drogue charge */
358 ao_ignite(ao_igniter_drogue);
360 /* slow down the telemetry system */
361 ao_telemetry_set_interval(AO_TELEMETRY_INTERVAL_RECOVER);
363 /* slow down the ADC sample rate */
364 ao_timer_set_adc_interval(10);
367 * Start recording min/max accel and pres for a while
368 * to figure out when the rocket has landed
370 /* Set the 'last' limits to max range to prevent
371 * early resting detection
373 ao_interval_min_accel = 0;
374 ao_interval_max_accel = 0x7fff;
375 ao_interval_min_pres = 0;
376 ao_interval_max_pres = 0x7fff;
378 /* initialize interval values */
379 ao_interval_end = ao_flight_tick + AO_INTERVAL_TICKS;
381 ao_interval_cur_min_pres = ao_interval_cur_max_pres = ao_flight_pres;
382 ao_interval_cur_min_accel = ao_interval_cur_max_accel = ao_flight_accel;
384 /* and enter drogue state */
385 ao_flight_state = ao_flight_drogue;
386 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
390 case ao_flight_drogue:
392 /* drogue to main deploy:
394 * barometer: reach main deploy altitude
396 * Would like to use the accelerometer for this test, but
397 * the orientation of the flight computer is unknown after
398 * drogue deploy, so we ignore it. Could also detect
399 * high descent rate using the pressure sensor to
400 * recognize drogue deploy failure and eject the main
401 * at that point. Perhaps also use the drogue sense lines
402 * to notice continutity?
404 if (ao_flight_pres >= ao_main_pres)
406 ao_ignite(ao_igniter_main);
407 ao_flight_state = ao_flight_main;
408 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
411 /* fall through... */
414 /* drogue/main to land:
416 * accelerometer: value stable
418 * barometer: altitude stable and within 1000m of the launch altitude
421 if (ao_flight_pres < ao_interval_cur_min_pres)
422 ao_interval_cur_min_pres = ao_flight_pres;
423 if (ao_flight_pres > ao_interval_cur_max_pres)
424 ao_interval_cur_max_pres = ao_flight_pres;
425 if (ao_flight_accel < ao_interval_cur_min_accel)
426 ao_interval_cur_min_accel = ao_flight_accel;
427 if (ao_flight_accel > ao_interval_cur_max_accel)
428 ao_interval_cur_max_accel = ao_flight_accel;
430 if ((int16_t) (ao_flight_tick - ao_interval_end) >= 0) {
431 ao_interval_max_pres = ao_interval_cur_max_pres;
432 ao_interval_min_pres = ao_interval_cur_min_pres;
433 ao_interval_max_accel = ao_interval_cur_max_accel;
434 ao_interval_min_accel = ao_interval_cur_min_accel;
435 ao_interval_end = ao_flight_tick + AO_INTERVAL_TICKS;
436 ao_interval_cur_min_pres = ao_interval_cur_max_pres = ao_flight_pres;
437 ao_interval_cur_min_accel = ao_interval_cur_max_accel = ao_flight_accel;
439 if ((uint16_t) (ao_interval_max_accel - ao_interval_min_accel) < (uint16_t) ACCEL_INT_LAND &&
440 ao_flight_pres > ao_ground_pres - BARO_LAND &&
441 (uint16_t) (ao_interval_max_pres - ao_interval_min_pres) < (uint16_t) BARO_INT_LAND)
443 ao_flight_state = ao_flight_landed;
445 /* turn off the ADC capture */
446 ao_timer_set_adc_interval(0);
447 /* Enable RDF beacon */
450 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
454 case ao_flight_landed:
460 static __xdata struct ao_task flight_task;
465 ao_flight_state = ao_flight_startup;
466 ao_add_task(&flight_task, ao_flight, "flight");