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_wakeup(DATA_TO_XDATA(&ao_flight_adc));
150 ao_sleep(DATA_TO_XDATA(&ao_adc_head));
151 while (ao_flight_adc != ao_adc_head) {
152 __pdata uint8_t ticks;
153 __pdata int16_t ao_vel_change;
154 __xdata struct ao_adc *ao_adc;
155 ao_flight_prev_tick = ao_flight_tick;
157 /* Capture a sample */
158 ao_adc = &ao_adc_ring[ao_flight_adc];
159 ao_flight_tick = ao_adc->tick;
160 ao_raw_accel = ao_adc->accel;
163 * Ok, the math here is a bit tricky.
165 * ao_raw_accel: ADC output for acceleration
166 * ao_accel_ref: ADC output for the 5V reference.
167 * ao_cook_accel: Corrected acceleration value
168 * Vcc: 3.3V supply to the CC1111
169 * Vac: 5V supply to the accelerometer
170 * accel: input voltage to accelerometer ADC pin
171 * ref: input voltage to 5V reference ADC pin
174 * Measured acceleration is ratiometric to Vcc:
177 * ------------ = -----
180 * Measured 5v reference is also ratiometric to Vcc:
183 * ------------ = -----
187 * ao_accel_ref = 32767 * (ref / Vcc)
189 * Acceleration is measured ratiometric to the 5V supply,
190 * so what we want is:
192 * ao_cook_accel accel
193 * ------------- = -----
202 * = ------------ * ------------
205 * Multiply through by 32767:
207 * ao_raw_accel * 32767
208 * ao_cook_accel = --------------------
211 * Now, the tricky part. Getting this to compile efficiently
212 * and keeping all of the values in-range.
214 * First off, we need to use a shift of 16 instead of * 32767 as SDCC
215 * does the obvious optimizations for byte-granularity shifts:
217 * ao_cook_accel = (ao_raw_accel << 16) / ao_accel_ref
219 * Next, lets check our input ranges:
221 * 0 <= ao_raw_accel <= 0x7fff (singled ended ADC conversion)
222 * 0x7000 <= ao_accel_ref <= 0x7fff (the 5V ref value is close to 0x7fff)
224 * Plugging in our input ranges, we get an output range of 0 - 0x12490,
225 * which is 17 bits. That won't work. If we take the accel ref and shift
226 * by a bit, we'll change its range:
228 * 0xe000 <= ao_accel_ref<<1 <= 0xfffe
230 * ao_cook_accel = (ao_raw_accel << 16) / (ao_accel_ref << 1)
232 * Now the output range is 0 - 0x9248, which nicely fits in 16 bits. It
233 * is, however, one bit too large for our signed computations. So, we
234 * take the result and shift that by a bit:
236 * ao_cook_accel = ((ao_raw_accel << 16) / (ao_accel_ref << 1)) >> 1
238 * This finally creates an output range of 0 - 0x4924. As the ADC only
239 * provides 11 bits of data, we haven't actually lost any precision,
240 * just dropped a bit of noise off the low end.
242 ao_raw_accel = (uint16_t) ((((uint32_t) ao_raw_accel << 16) / (ao_accel_ref[ao_flight_adc] << 1))) >> 1;
243 ao_adc->accel = ao_raw_accel;
245 ao_raw_pres = ao_adc->pres;
247 ao_flight_accel -= ao_flight_accel >> 4;
248 ao_flight_accel += ao_raw_accel >> 4;
249 ao_flight_pres -= ao_flight_pres >> 4;
250 ao_flight_pres += ao_raw_pres >> 4;
253 * The accelerometer is mounted so that
254 * acceleration yields negative values
255 * while deceleration yields positive values,
256 * so subtract instead of add.
258 ticks = ao_flight_tick - ao_flight_prev_tick;
259 ao_vel_change = ao_ground_accel - (((ao_raw_accel + 1) >> 1) + ((ao_raw_accel_prev + 1) >> 1));
260 ao_raw_accel_prev = ao_raw_accel;
262 /* one is a common interval */
264 ao_flight_vel += (int32_t) ao_vel_change;
266 ao_flight_vel += (int32_t) ao_vel_change * (int32_t) ticks;
268 ao_flight_adc = ao_adc_ring_next(ao_flight_adc);
271 if (ao_flight_pres < ao_min_pres)
272 ao_min_pres = ao_flight_pres;
273 if (ao_flight_vel >= 0) {
274 if (ao_flight_vel < ao_min_vel)
275 ao_min_vel = ao_flight_vel;
277 if (-ao_flight_vel < ao_min_vel)
278 ao_min_vel = -ao_flight_vel;
281 switch (ao_flight_state) {
282 case ao_flight_startup:
286 * Collect 512 samples of acceleration and pressure
287 * data and average them to find the resting values
289 if (nsamples < 512) {
290 ao_raw_accel_sum += ao_raw_accel;
291 ao_raw_pres_sum += ao_raw_pres;
295 ao_ground_accel = ao_raw_accel_sum >> 9;
296 ao_ground_pres = ao_raw_pres_sum >> 9;
297 ao_min_pres = ao_ground_pres;
299 ao_main_pres = ao_altitude_to_pres(ao_pres_to_altitude(ao_ground_pres) + ao_config.main_deploy);
300 ao_accel_2g = ao_config.accel_minus_g - ao_config.accel_plus_g;
303 ao_old_vel = ao_flight_vel;
304 ao_old_vel_tick = ao_flight_tick;
306 /* Check to see what mode we should go to.
307 * - Invalid mode if accel cal appears to be out
308 * - pad mode if we're upright,
309 * - idle mode otherwise
312 if (ao_config.accel_plus_g == 0 ||
313 ao_config.accel_minus_g == 0 ||
314 ao_flight_accel < ao_config.accel_plus_g - ACCEL_NOSE_UP ||
315 ao_flight_accel > ao_config.accel_minus_g + ACCEL_NOSE_UP)
317 /* Detected an accel value outside -1.5g to 1.5g
318 * (or uncalibrated values), so we go into invalid mode
320 ao_flight_state = ao_flight_invalid;
321 /* Allow packet mode in invalid flight state,
322 * Still need to be able to fix the problem!
324 ao_packet_slave_start();
326 } else if (ao_flight_accel < ao_config.accel_plus_g + ACCEL_NOSE_UP &&
327 !ao_flight_force_idle)
329 /* Set pad mode - we can fly! */
330 ao_flight_state = ao_flight_pad;
332 /* Disable the USB controller in flight mode
337 /* Turn on telemetry system */
339 ao_telemetry_set_interval(AO_TELEMETRY_INTERVAL_PAD);
341 /* signal successful initialization by turning off the LED */
342 ao_led_off(AO_LED_RED);
345 ao_flight_state = ao_flight_idle;
347 /* Turn on packet system in idle mode */
348 ao_packet_slave_start();
350 /* signal successful initialization by turning off the LED */
351 ao_led_off(AO_LED_RED);
353 /* wakeup threads due to state change */
354 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
361 * Once a second, remove any velocity from
364 if ((int16_t) (ao_flight_tick - ao_old_vel_tick) >= AO_SEC_TO_TICKS(1)) {
365 ao_old_vel_tick = ao_flight_tick;
366 ao_flight_vel -= ao_old_vel;
367 ao_old_vel = ao_flight_vel;
371 * accelerometer: > 2g AND velocity > 5m/s
373 * barometer: > 20m vertical motion
375 * The accelerometer should always detect motion before
376 * the barometer, but we use both to make sure this
377 * transition is detected
379 if ((ao_flight_accel < ao_ground_accel - ACCEL_BOOST &&
380 ao_flight_vel > ACCEL_VEL_BOOST) ||
381 ao_flight_pres < ao_ground_pres - BARO_LAUNCH)
383 ao_flight_state = ao_flight_boost;
384 ao_launch_tick = ao_flight_tick;
386 /* start logging data */
389 /* Increase telemetry rate */
390 ao_telemetry_set_interval(AO_TELEMETRY_INTERVAL_FLIGHT);
392 /* disable RDF beacon */
395 /* Record current GPS position by waking up GPS log tasks */
396 ao_wakeup(&ao_gps_data);
397 ao_wakeup(&ao_gps_tracking_data);
399 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
403 case ao_flight_boost:
407 * accelerometer: start to fall at > 1/4 G
409 * time: boost for more than 15 seconds
411 * Detects motor burn out by the switch from acceleration to
412 * deceleration, or by waiting until the maximum burn duration
413 * (15 seconds) has past.
415 if (ao_flight_accel > ao_ground_accel + ACCEL_COAST ||
416 (int16_t) (ao_flight_tick - ao_launch_tick) > BOOST_TICKS_MAX)
418 ao_flight_state = ao_flight_fast;
419 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
427 * accelerometer: integrated velocity < 200 m/s
429 * barometer: fall at least 500m from max altitude
431 * This extra state is required to avoid mis-detecting
432 * apogee due to mach transitions.
434 * XXX this is essentially a single-detector test
435 * as the 500m altitude change would likely result
436 * in a loss of the rocket. More data on precisely
437 * how big a pressure change the mach transition
438 * generates would be useful here.
440 if (ao_flight_vel < ACCEL_VEL_MACH ||
441 ao_flight_pres > ao_min_pres + BARO_COAST)
443 /* set min velocity to current velocity for
446 ao_min_vel = abs(ao_flight_vel);
447 ao_flight_state = ao_flight_coast;
448 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
451 case ao_flight_coast:
453 /* apogee detect: coast to drogue deploy:
455 * barometer: fall at least 10m
457 * It would be nice to use the accelerometer
458 * to detect apogee as well, but tests have
459 * shown that flights far from vertical would
460 * grossly mis-detect apogee. So, for now,
461 * we'll trust to a single sensor for this test
463 if (ao_flight_pres > ao_min_pres + BARO_APOGEE)
465 /* ignite the drogue charge */
466 ao_ignite(ao_igniter_drogue);
468 /* slow down the telemetry system */
469 ao_telemetry_set_interval(AO_TELEMETRY_INTERVAL_RECOVER);
471 /* slow down the ADC sample rate */
472 ao_timer_set_adc_interval(10);
475 * Start recording min/max accel and pres for a while
476 * to figure out when the rocket has landed
478 /* Set the 'last' limits to max range to prevent
479 * early resting detection
481 ao_interval_min_accel = 0;
482 ao_interval_max_accel = 0x7fff;
483 ao_interval_min_pres = 0;
484 ao_interval_max_pres = 0x7fff;
486 /* initialize interval values */
487 ao_interval_end = ao_flight_tick + AO_INTERVAL_TICKS;
489 ao_interval_cur_min_pres = ao_interval_cur_max_pres = ao_flight_pres;
490 ao_interval_cur_min_accel = ao_interval_cur_max_accel = ao_flight_accel;
492 /* and enter drogue state */
493 ao_flight_state = ao_flight_drogue;
494 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
498 case ao_flight_drogue:
500 /* drogue to main deploy:
502 * barometer: reach main deploy altitude
504 * Would like to use the accelerometer for this test, but
505 * the orientation of the flight computer is unknown after
506 * drogue deploy, so we ignore it. Could also detect
507 * high descent rate using the pressure sensor to
508 * recognize drogue deploy failure and eject the main
509 * at that point. Perhaps also use the drogue sense lines
510 * to notice continutity?
512 if (ao_flight_pres >= ao_main_pres)
514 ao_ignite(ao_igniter_main);
515 ao_flight_state = ao_flight_main;
516 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
519 /* fall through... */
522 /* drogue/main to land:
524 * accelerometer: value stable
526 * barometer: altitude stable and within 1000m of the launch altitude
529 if (ao_flight_pres < ao_interval_cur_min_pres)
530 ao_interval_cur_min_pres = ao_flight_pres;
531 if (ao_flight_pres > ao_interval_cur_max_pres)
532 ao_interval_cur_max_pres = ao_flight_pres;
533 if (ao_flight_accel < ao_interval_cur_min_accel)
534 ao_interval_cur_min_accel = ao_flight_accel;
535 if (ao_flight_accel > ao_interval_cur_max_accel)
536 ao_interval_cur_max_accel = ao_flight_accel;
538 if ((int16_t) (ao_flight_tick - ao_interval_end) >= 0) {
539 ao_interval_max_pres = ao_interval_cur_max_pres;
540 ao_interval_min_pres = ao_interval_cur_min_pres;
541 ao_interval_max_accel = ao_interval_cur_max_accel;
542 ao_interval_min_accel = ao_interval_cur_min_accel;
543 ao_interval_end = ao_flight_tick + AO_INTERVAL_TICKS;
544 ao_interval_cur_min_pres = ao_interval_cur_max_pres = ao_flight_pres;
545 ao_interval_cur_min_accel = ao_interval_cur_max_accel = ao_flight_accel;
547 if ((uint16_t) (ao_interval_max_accel - ao_interval_min_accel) < (uint16_t) ACCEL_INT_LAND &&
548 ao_flight_pres > ao_ground_pres - BARO_LAND &&
549 (uint16_t) (ao_interval_max_pres - ao_interval_min_pres) < (uint16_t) BARO_INT_LAND)
551 ao_flight_state = ao_flight_landed;
553 /* turn off the ADC capture */
554 ao_timer_set_adc_interval(0);
555 /* Enable RDF beacon */
558 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
562 case ao_flight_landed:
568 static __xdata struct ao_task flight_task;
573 ao_flight_state = ao_flight_startup;
574 ao_add_task(&flight_task, ao_flight, "flight");