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 /* Accelerometer calibration
55 * We're sampling the accelerometer through a resistor divider which
56 * consists of 5k and 10k resistors. This multiplies the values by 2/3.
57 * That goes into the cc1111 A/D converter, which is running at 11 bits
58 * of precision with the bits in the MSB of the 16 bit value. Only positive
59 * values are used, so values should range from 0-32752 for 0-3.3V. The
60 * specs say we should see 40mV/g (uncalibrated), multiply by 2/3 for what
61 * the A/D converter sees (26.67 mV/g). We should see 32752/3300 counts/mV,
62 * for a final computation of:
64 * 26.67 mV/g * 32767/3300 counts/mV = 264.8 counts/g
66 * Zero g was measured at 16000 (we would expect 16384).
67 * Note that this value is only require to tell if the
68 * rocket is standing upright. Once that is determined,
69 * the value of the accelerometer is averaged for 100 samples
70 * to find the resting accelerometer value, which is used
71 * for all further flight computations
74 #define GRAVITY 9.80665
75 /* convert m/s to velocity count */
76 #define VEL_MPS_TO_COUNT(mps) (((int32_t) (((mps) / GRAVITY) * (AO_HERTZ/2))) * (int32_t) ao_accel_2g)
78 #define ACCEL_NOSE_UP (ao_accel_2g >> 2)
79 #define ACCEL_BOOST ao_accel_2g
80 #define ACCEL_COAST (ao_accel_2g >> 3)
81 #define ACCEL_INT_LAND (ao_accel_2g >> 3)
82 #define ACCEL_VEL_MACH VEL_MPS_TO_COUNT(200)
83 #define ACCEL_VEL_BOOST VEL_MPS_TO_COUNT(5)
85 int32_t accel_vel_mach;
86 int32_t accel_vel_boost;
89 * Barometer calibration
91 * We directly sample the barometer. The specs say:
93 * Pressure range: 15-115 kPa
94 * Voltage at 115kPa: 2.82
95 * Output scale: 27mV/kPa
97 * If we want to detect launch with the barometer, we need
98 * a large enough bump to not be fooled by noise. At typical
99 * launch elevations (0-2000m), a 200Pa pressure change cooresponds
100 * to about a 20m elevation change. This is 5.4mV, or about 3LSB.
101 * As all of our calculations are done in 16 bits, we'll actually see a change
102 * of 16 times this though
104 * 27 mV/kPa * 32767 / 3300 counts/mV = 268.1 counts/kPa
108 #define BARO_LAUNCH (BARO_kPa / 5) /* .2kPa, or about 20m */
109 #define BARO_APOGEE (BARO_kPa / 10) /* .1kPa, or about 10m */
110 #define BARO_COAST (BARO_kPa * 5) /* 5kpa, or about 500m */
111 #define BARO_MAIN (BARO_kPa) /* 1kPa, or about 100m */
112 #define BARO_INT_LAND (BARO_kPa / 20) /* .05kPa, or about 5m */
113 #define BARO_LAND (BARO_kPa * 10) /* 10kPa or about 1000m */
115 /* We also have a clock, which can be used to sanity check things in
116 * case of other failures
119 #define BOOST_TICKS_MAX AO_SEC_TO_TICKS(15)
121 /* This value is scaled in a weird way. It's a running total of accelerometer
122 * readings minus the ground accelerometer reading. That means it measures
123 * velocity, and quite accurately too. As it gets updated 100 times a second,
126 __pdata int32_t ao_flight_vel;
127 __pdata int32_t ao_min_vel;
128 __pdata int32_t ao_old_vel;
129 __pdata int16_t ao_old_vel_tick;
130 __xdata int32_t ao_raw_accel_sum, ao_raw_pres_sum;
132 /* Landing is detected by getting constant readings from both pressure and accelerometer
133 * for a fairly long time (AO_INTERVAL_TICKS)
135 #define AO_INTERVAL_TICKS AO_SEC_TO_TICKS(5)
137 #define abs(a) ((a) < 0 ? -(a) : (a))
142 __pdata static uint16_t nsamples = 0;
144 ao_flight_adc = ao_adc_head;
145 ao_raw_accel_prev = 0;
150 ao_sleep(&ao_adc_ring);
151 while (ao_flight_adc != ao_adc_head) {
152 __pdata uint8_t ticks;
153 __pdata int16_t ao_vel_change;
154 ao_flight_prev_tick = ao_flight_tick;
156 /* Capture a sample */
157 ao_raw_accel = ao_adc_ring[ao_flight_adc].accel;
158 ao_raw_pres = ao_adc_ring[ao_flight_adc].pres;
159 ao_flight_tick = ao_adc_ring[ao_flight_adc].tick;
161 ao_flight_accel -= ao_flight_accel >> 4;
162 ao_flight_accel += ao_raw_accel >> 4;
163 ao_flight_pres -= ao_flight_pres >> 4;
164 ao_flight_pres += ao_raw_pres >> 4;
167 * The accelerometer is mounted so that
168 * acceleration yields negative values
169 * while deceleration yields positive values,
170 * so subtract instead of add.
172 ticks = ao_flight_tick - ao_flight_prev_tick;
173 ao_vel_change = ao_ground_accel - (((ao_raw_accel + 1) >> 1) + ((ao_raw_accel_prev + 1) >> 1));
174 ao_raw_accel_prev = ao_raw_accel;
176 /* one is a common interval */
178 ao_flight_vel += (int32_t) ao_vel_change;
180 ao_flight_vel += (int32_t) ao_vel_change * (int32_t) ticks;
182 ao_flight_adc = ao_adc_ring_next(ao_flight_adc);
185 if (ao_flight_pres < ao_min_pres)
186 ao_min_pres = ao_flight_pres;
187 if (ao_flight_vel >= 0) {
188 if (ao_flight_vel < ao_min_vel)
189 ao_min_vel = ao_flight_vel;
191 if (-ao_flight_vel < ao_min_vel)
192 ao_min_vel = -ao_flight_vel;
195 switch (ao_flight_state) {
196 case ao_flight_startup:
200 * Collect 1000 samples of acceleration and pressure
201 * data and average them to find the resting values
203 if (nsamples < 1000) {
204 ao_raw_accel_sum += ao_raw_accel;
205 ao_raw_pres_sum += ao_raw_pres;
209 ao_ground_accel = (ao_raw_accel_sum / nsamples);
210 ao_ground_pres = (ao_raw_pres_sum / nsamples);
211 ao_min_pres = ao_ground_pres;
213 ao_main_pres = ao_altitude_to_pres(ao_pres_to_altitude(ao_ground_pres) + ao_config.main_deploy);
214 ao_accel_2g = ao_config.accel_minus_g - ao_config.accel_plus_g;
215 accel_vel_mach = ACCEL_VEL_MACH;
216 accel_vel_boost = ACCEL_VEL_BOOST;
219 ao_old_vel = ao_flight_vel;
220 ao_old_vel_tick = ao_flight_tick;
222 /* Go to pad state if the nose is pointing up */
224 if (ao_config.accel_plus_g != 0 && ao_config.accel_minus_g != 0 &&
225 ao_flight_accel < ao_config.accel_plus_g + ACCEL_NOSE_UP)
227 /* Disable the USB controller in flight mode
232 /* Turn on telemetry system
235 ao_telemetry_set_interval(AO_TELEMETRY_INTERVAL_PAD);
237 ao_flight_state = ao_flight_pad;
238 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
240 ao_flight_state = ao_flight_idle;
242 /* Turn on packet system in idle mode
244 ao_packet_slave_start();
245 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
247 /* signal successful initialization by turning off the LED */
248 ao_led_off(AO_LED_RED);
254 * Once a second, remove any velocity from
257 if ((int16_t) (ao_flight_tick - ao_old_vel_tick) >= AO_SEC_TO_TICKS(1)) {
258 ao_old_vel_tick = ao_flight_tick;
259 ao_flight_vel -= ao_old_vel;
260 ao_old_vel = ao_flight_vel;
264 * accelerometer: > 2g AND velocity > 5m/s
266 * barometer: > 20m vertical motion
268 * The accelerometer should always detect motion before
269 * the barometer, but we use both to make sure this
270 * transition is detected
272 if ((ao_flight_accel < ao_ground_accel - ACCEL_BOOST &&
273 ao_flight_vel > ACCEL_VEL_BOOST) ||
274 ao_flight_pres < ao_ground_pres - BARO_LAUNCH)
276 ao_flight_state = ao_flight_boost;
277 ao_launch_tick = ao_flight_tick;
279 /* start logging data */
282 /* Increase telemetry rate */
283 ao_telemetry_set_interval(AO_TELEMETRY_INTERVAL_FLIGHT);
285 /* disable RDF beacon */
288 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
292 case ao_flight_boost:
296 * accelerometer: start to fall at > 1/4 G
298 * time: boost for more than 15 seconds
300 * Detects motor burn out by the switch from acceleration to
301 * deceleration, or by waiting until the maximum burn duration
302 * (15 seconds) has past.
304 if (ao_flight_accel > ao_ground_accel + ACCEL_COAST ||
305 (int16_t) (ao_flight_tick - ao_launch_tick) > BOOST_TICKS_MAX)
307 ao_flight_state = ao_flight_fast;
308 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
316 * accelerometer: integrated velocity < 200 m/s
318 * barometer: fall at least 500m from max altitude
320 * This extra state is required to avoid mis-detecting
321 * apogee due to mach transitions.
323 * XXX this is essentially a single-detector test
324 * as the 500m altitude change would likely result
325 * in a loss of the rocket. More data on precisely
326 * how big a pressure change the mach transition
327 * generates would be useful here.
329 if (ao_flight_vel < ACCEL_VEL_MACH ||
330 ao_flight_pres > ao_min_pres + BARO_COAST)
332 /* set min velocity to current velocity for
335 ao_min_vel = abs(ao_flight_vel);
336 ao_flight_state = ao_flight_coast;
337 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
340 case ao_flight_coast:
342 /* apogee detect: coast to drogue deploy:
344 * barometer: fall at least 10m
346 * It would be nice to use the accelerometer
347 * to detect apogee as well, but tests have
348 * shown that flights far from vertical would
349 * grossly mis-detect apogee. So, for now,
350 * we'll trust to a single sensor for this test
352 if (ao_flight_pres > ao_min_pres + BARO_APOGEE)
354 /* ignite the drogue charge */
355 ao_ignite(ao_igniter_drogue);
357 /* slow down the telemetry system */
358 ao_telemetry_set_interval(AO_TELEMETRY_INTERVAL_RECOVER);
360 /* slow down the ADC sample rate */
361 ao_timer_set_adc_interval(10);
364 * Start recording min/max accel and pres for a while
365 * to figure out when the rocket has landed
367 /* Set the 'last' limits to max range to prevent
368 * early resting detection
370 ao_interval_min_accel = 0;
371 ao_interval_max_accel = 0x7fff;
372 ao_interval_min_pres = 0;
373 ao_interval_max_pres = 0x7fff;
375 /* initialize interval values */
376 ao_interval_end = ao_flight_tick + AO_INTERVAL_TICKS;
378 ao_interval_cur_min_pres = ao_interval_cur_max_pres = ao_flight_pres;
379 ao_interval_cur_min_accel = ao_interval_cur_max_accel = ao_flight_accel;
381 /* and enter drogue state */
382 ao_flight_state = ao_flight_drogue;
383 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
387 case ao_flight_drogue:
389 /* drogue to main deploy:
391 * barometer: reach main deploy altitude
393 * Would like to use the accelerometer for this test, but
394 * the orientation of the flight computer is unknown after
395 * drogue deploy, so we ignore it. Could also detect
396 * high descent rate using the pressure sensor to
397 * recognize drogue deploy failure and eject the main
398 * at that point. Perhaps also use the drogue sense lines
399 * to notice continutity?
401 if (ao_flight_pres >= ao_main_pres)
403 ao_ignite(ao_igniter_main);
404 ao_flight_state = ao_flight_main;
405 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
408 /* fall through... */
411 /* drogue/main to land:
413 * accelerometer: value stable
415 * barometer: altitude stable and within 1000m of the launch altitude
418 if (ao_flight_pres < ao_interval_cur_min_pres)
419 ao_interval_cur_min_pres = ao_flight_pres;
420 if (ao_flight_pres > ao_interval_cur_max_pres)
421 ao_interval_cur_max_pres = ao_flight_pres;
422 if (ao_flight_accel < ao_interval_cur_min_accel)
423 ao_interval_cur_min_accel = ao_flight_accel;
424 if (ao_flight_accel > ao_interval_cur_max_accel)
425 ao_interval_cur_max_accel = ao_flight_accel;
427 if ((int16_t) (ao_flight_tick - ao_interval_end) >= 0) {
428 ao_interval_max_pres = ao_interval_cur_max_pres;
429 ao_interval_min_pres = ao_interval_cur_min_pres;
430 ao_interval_max_accel = ao_interval_cur_max_accel;
431 ao_interval_min_accel = ao_interval_cur_min_accel;
432 ao_interval_end = ao_flight_tick + AO_INTERVAL_TICKS;
433 ao_interval_cur_min_pres = ao_interval_cur_max_pres = ao_flight_pres;
434 ao_interval_cur_min_accel = ao_interval_cur_max_accel = ao_flight_accel;
436 if ((uint16_t) (ao_interval_max_accel - ao_interval_min_accel) < (uint16_t) ACCEL_INT_LAND &&
437 ao_flight_pres > ao_ground_pres - BARO_LAND &&
438 (uint16_t) (ao_interval_max_pres - ao_interval_min_pres) < (uint16_t) BARO_INT_LAND)
440 ao_flight_state = ao_flight_landed;
442 /* turn off the ADC capture */
443 ao_timer_set_adc_interval(0);
444 /* Enable RDF beacon */
447 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
451 case ao_flight_landed:
457 static __xdata struct ao_task flight_task;
462 ao_flight_state = ao_flight_startup;
463 ao_interval_min_accel = 0;
464 ao_interval_max_accel = 0x7fff;
465 ao_interval_min_pres = 0;
466 ao_interval_max_pres = 0x7fff;
467 ao_interval_end = AO_INTERVAL_TICKS;
469 ao_add_task(&flight_task, ao_flight, "flight");