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
23 #error Please define HAS_ACCEL
27 #error Please define HAS_GPS
31 #error Please define HAS_USB
34 /* Main flight thread. */
36 __pdata enum ao_flight_state ao_flight_state; /* current flight state */
37 __pdata uint16_t ao_flight_tick; /* time of last data */
38 __pdata uint16_t ao_flight_prev_tick; /* time of previous data */
39 __xdata int16_t ao_ground_pres; /* startup pressure */
40 __pdata uint16_t ao_launch_tick; /* time of launch detect */
42 __pdata int16_t ao_ground_accel; /* startup acceleration */
46 * track min/max data over a long interval to detect
49 __pdata uint16_t ao_interval_end;
50 __pdata int16_t ao_interval_min_height;
51 __pdata int16_t ao_interval_max_height;
53 __data uint8_t ao_flight_adc;
54 __pdata int16_t ao_raw_pres;
55 __xdata uint8_t ao_flight_force_idle;
58 __pdata int16_t ao_raw_accel, ao_raw_accel_prev;
59 __pdata int16_t ao_accel_2g;
61 /* Accelerometer calibration
63 * We're sampling the accelerometer through a resistor divider which
64 * consists of 5k and 10k resistors. This multiplies the values by 2/3.
65 * That goes into the cc1111 A/D converter, which is running at 11 bits
66 * of precision with the bits in the MSB of the 16 bit value. Only positive
67 * values are used, so values should range from 0-32752 for 0-3.3V. The
68 * specs say we should see 40mV/g (uncalibrated), multiply by 2/3 for what
69 * the A/D converter sees (26.67 mV/g). We should see 32752/3300 counts/mV,
70 * for a final computation of:
72 * 26.67 mV/g * 32767/3300 counts/mV = 264.8 counts/g
74 * Zero g was measured at 16000 (we would expect 16384).
75 * Note that this value is only require to tell if the
76 * rocket is standing upright. Once that is determined,
77 * the value of the accelerometer is averaged for 100 samples
78 * to find the resting accelerometer value, which is used
79 * for all further flight computations
82 #define GRAVITY 9.80665
84 #define ACCEL_NOSE_UP (ao_accel_2g >> 2)
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
107 /* We also have a clock, which can be used to sanity check things in
108 * case of other failures
111 #define BOOST_TICKS_MAX AO_SEC_TO_TICKS(15)
113 #define to_fix16(x) ((int16_t) ((x) * 65536.0 + 0.5))
114 #define to_fix32(x) ((int32_t) ((x) * 65536.0 + 0.5))
115 #define from_fix(x) ((x) >> 16)
117 #include "ao_kalman.h"
119 __pdata int16_t ao_ground_height;
120 __pdata int16_t ao_height;
121 __pdata int16_t ao_speed;
122 __pdata int16_t ao_accel;
123 __pdata int16_t ao_max_height;
125 static __pdata int32_t ao_k_height;
126 static __pdata int32_t ao_k_speed;
127 static __pdata int32_t ao_k_accel;
129 #define AO_K_STEP_100 to_fix16(0.01)
130 #define AO_K_STEP_2_2_100 to_fix16(0.00005)
132 #define AO_K_STEP_10 to_fix16(0.1)
133 #define AO_K_STEP_2_2_10 to_fix16(0.005)
136 * Above this height, the baro sensor doesn't work
138 #define AO_MAX_BARO_HEIGHT 12000
141 * Above this speed, baro measurements are unreliable
143 #define AO_MAX_BARO_SPEED 300
146 ao_kalman_predict(void)
148 #ifdef AO_FLIGHT_TEST
149 if (ao_flight_tick - ao_flight_prev_tick > 5) {
150 ao_k_height += ((int32_t) ao_speed * AO_K_STEP_10 +
151 (int32_t) ao_accel * AO_K_STEP_2_2_10) >> 4;
152 ao_k_speed += (int32_t) ao_accel * AO_K_STEP_10;
157 ao_k_height += ((int32_t) ao_speed * AO_K_STEP_100 +
158 (int32_t) ao_accel * AO_K_STEP_2_2_100) >> 4;
159 ao_k_speed += (int32_t) ao_accel * AO_K_STEP_100;
162 static __pdata int16_t ao_error_h;
163 static __pdata int16_t ao_raw_alt;
164 static __pdata int16_t ao_raw_height;
165 static __pdata int16_t ao_error_h_sq_avg;
168 ao_kalman_err_height(void)
171 int16_t height_distrust;
173 int16_t speed_distrust;
176 ao_error_h = ao_raw_height - (int16_t) (ao_k_height >> 16);
183 ao_error_h_sq_avg -= ao_error_h_sq_avg >> 4;
184 ao_error_h_sq_avg += (e * e) >> 4;
186 height_distrust = ao_raw_height - AO_MAX_BARO_HEIGHT;
188 speed_distrust = (ao_speed - AO_MS_TO_SPEED(AO_MAX_BARO_SPEED)) >> 4;
189 if (speed_distrust <= 0)
191 else if (speed_distrust > height_distrust)
192 height_distrust = speed_distrust;
194 if (height_distrust <= 0)
197 if (height_distrust) {
198 if (height_distrust > 0x100)
199 height_distrust = 0x100;
200 ao_error_h = (int16_t) ((int32_t) ao_error_h * (0x100 - height_distrust)) >> 8;
205 ao_kalman_correct_baro(void)
207 ao_kalman_err_height();
208 #ifdef AO_FLIGHT_TEST
209 if (ao_flight_tick - ao_flight_prev_tick > 5) {
210 ao_k_height += (int32_t) AO_BARO_K0_10 * ao_error_h;
211 ao_k_speed += (int32_t) AO_BARO_K1_10 * ao_error_h;
212 ao_k_accel += (int32_t) AO_BARO_K2_10 * ao_error_h;
216 ao_k_height += (int32_t) AO_BARO_K0_100 * ao_error_h;
217 ao_k_speed += (int32_t) AO_BARO_K1_100 * ao_error_h;
218 ao_k_accel += (int32_t) AO_BARO_K2_100 * ao_error_h;
222 static __pdata int16_t ao_error_a;
223 static __pdata int32_t ao_accel_scale;
226 ao_kalman_err_accel(void)
230 accel = (ao_ground_accel - ao_raw_accel) * ao_accel_scale;
232 /* Can't use ao_accel here as it is the pre-prediction value still */
233 ao_error_a = (accel - ao_k_accel) >> 16;
237 ao_kalman_correct_both(void)
239 ao_kalman_err_height();
240 ao_kalman_err_accel();
242 #ifdef AO_FLIGHT_TEST
243 if (ao_flight_tick - ao_flight_prev_tick > 5) {
245 (int32_t) AO_BOTH_K00_10 * ao_error_h +
246 (int32_t) (AO_BOTH_K01_10 >> 4) * ao_error_a;
248 ((int32_t) AO_BOTH_K10_10 << 4) * ao_error_h +
249 (int32_t) AO_BOTH_K11_10 * ao_error_a;
251 ((int32_t) AO_BOTH_K20_10 << 4) * ao_error_h +
252 (int32_t) AO_BOTH_K21_10 * ao_error_a;
257 (int32_t) AO_BOTH_K00_100 * ao_error_h +
258 (int32_t) AO_BOTH_K01_100 * ao_error_a;
260 (int32_t) AO_BOTH_K10_100 * ao_error_h +
261 (int32_t) AO_BOTH_K11_100 * ao_error_a;
263 (int32_t) AO_BOTH_K20_100 * ao_error_h +
264 (int32_t) AO_BOTH_K21_100 * ao_error_a;
268 ao_kalman_correct_accel(void)
270 ao_kalman_err_accel();
272 #ifdef AO_FLIGHT_TEST
273 if (ao_flight_tick - ao_flight_prev_tick > 5) {
274 ao_k_height +=(int32_t) AO_ACCEL_K0_10 * ao_error_a;
275 ao_k_speed += (int32_t) AO_ACCEL_K1_10 * ao_error_a;
276 ao_k_accel += (int32_t) AO_ACCEL_K2_10 * ao_error_a;
280 ao_k_height += (int32_t) AO_ACCEL_K0_100 * ao_error_a;
281 ao_k_speed += (int32_t) AO_ACCEL_K1_100 * ao_error_a;
282 ao_k_accel += (int32_t) AO_ACCEL_K2_100 * ao_error_a;
284 #endif /* HAS_ACCEL */
286 __xdata int32_t ao_raw_pres_sum;
289 __xdata int32_t ao_raw_accel_sum;
292 /* Landing is detected by getting constant readings from both pressure and accelerometer
293 * for a fairly long time (AO_INTERVAL_TICKS)
295 #define AO_INTERVAL_TICKS AO_SEC_TO_TICKS(5)
297 #define abs(a) ((a) < 0 ? -(a) : (a))
302 __pdata static uint16_t nsamples = 0;
304 ao_flight_adc = ao_adc_head;
307 ao_raw_accel_prev = 0;
312 ao_wakeup(DATA_TO_XDATA(&ao_flight_adc));
313 ao_sleep(DATA_TO_XDATA(&ao_adc_head));
314 while (ao_flight_adc != ao_adc_head) {
315 __xdata struct ao_adc *ao_adc;
316 ao_flight_prev_tick = ao_flight_tick;
318 /* Capture a sample */
319 ao_adc = &ao_adc_ring[ao_flight_adc];
320 ao_flight_tick = ao_adc->tick;
321 ao_raw_pres = ao_adc->pres;
322 ao_raw_alt = ao_pres_to_altitude(ao_raw_pres);
323 ao_raw_height = ao_raw_alt - ao_ground_height;
325 ao_raw_accel = ao_adc->accel;
328 * Ok, the math here is a bit tricky.
330 * ao_raw_accel: ADC output for acceleration
331 * ao_accel_ref: ADC output for the 5V reference.
332 * ao_cook_accel: Corrected acceleration value
333 * Vcc: 3.3V supply to the CC1111
334 * Vac: 5V supply to the accelerometer
335 * accel: input voltage to accelerometer ADC pin
336 * ref: input voltage to 5V reference ADC pin
339 * Measured acceleration is ratiometric to Vcc:
342 * ------------ = -----
345 * Measured 5v reference is also ratiometric to Vcc:
348 * ------------ = -----
352 * ao_accel_ref = 32767 * (ref / Vcc)
354 * Acceleration is measured ratiometric to the 5V supply,
355 * so what we want is:
357 * ao_cook_accel accel
358 * ------------- = -----
367 * = ------------ * ------------
370 * Multiply through by 32767:
372 * ao_raw_accel * 32767
373 * ao_cook_accel = --------------------
376 * Now, the tricky part. Getting this to compile efficiently
377 * and keeping all of the values in-range.
379 * First off, we need to use a shift of 16 instead of * 32767 as SDCC
380 * does the obvious optimizations for byte-granularity shifts:
382 * ao_cook_accel = (ao_raw_accel << 16) / ao_accel_ref
384 * Next, lets check our input ranges:
386 * 0 <= ao_raw_accel <= 0x7fff (singled ended ADC conversion)
387 * 0x7000 <= ao_accel_ref <= 0x7fff (the 5V ref value is close to 0x7fff)
389 * Plugging in our input ranges, we get an output range of 0 - 0x12490,
390 * which is 17 bits. That won't work. If we take the accel ref and shift
391 * by a bit, we'll change its range:
393 * 0xe000 <= ao_accel_ref<<1 <= 0xfffe
395 * ao_cook_accel = (ao_raw_accel << 16) / (ao_accel_ref << 1)
397 * Now the output range is 0 - 0x9248, which nicely fits in 16 bits. It
398 * is, however, one bit too large for our signed computations. So, we
399 * take the result and shift that by a bit:
401 * ao_cook_accel = ((ao_raw_accel << 16) / (ao_accel_ref << 1)) >> 1
403 * This finally creates an output range of 0 - 0x4924. As the ADC only
404 * provides 11 bits of data, we haven't actually lost any precision,
405 * just dropped a bit of noise off the low end.
407 ao_raw_accel = (uint16_t) ((((uint32_t) ao_raw_accel << 16) / (ao_accel_ref[ao_flight_adc] << 1))) >> 1;
408 ao_adc->accel = ao_raw_accel;
412 if (ao_flight_state > ao_flight_idle) {
415 if (ao_flight_state <= ao_flight_coast) {
417 ao_kalman_correct_accel();
419 ao_kalman_correct_both();
423 ao_kalman_correct_baro();
424 ao_height = from_fix(ao_k_height);
425 ao_speed = from_fix(ao_k_speed);
426 ao_accel = from_fix(ao_k_accel);
427 if (ao_height > ao_max_height)
428 ao_max_height = ao_height;
430 ao_flight_adc = ao_adc_ring_next(ao_flight_adc);
433 switch (ao_flight_state) {
434 case ao_flight_startup:
438 * Collect 512 samples of acceleration and pressure
439 * data and average them to find the resting values
441 if (nsamples < 512) {
443 ao_raw_accel_sum += ao_raw_accel;
445 ao_raw_pres_sum += ao_raw_pres;
451 ao_ground_accel = ao_raw_accel_sum >> 9;
452 ao_accel_2g = ao_config.accel_minus_g - ao_config.accel_plus_g;
453 ao_accel_scale = to_fix32(GRAVITY * 2 * 16) / ao_accel_2g;
455 ao_ground_pres = ao_raw_pres_sum >> 9;
456 ao_ground_height = ao_pres_to_altitude(ao_ground_pres);
458 /* Check to see what mode we should go to.
459 * - Invalid mode if accel cal appears to be out
460 * - pad mode if we're upright,
461 * - idle mode otherwise
464 if (ao_config.accel_plus_g == 0 ||
465 ao_config.accel_minus_g == 0 ||
466 ao_ground_accel < ao_config.accel_plus_g - ACCEL_NOSE_UP ||
467 ao_ground_accel > ao_config.accel_minus_g + ACCEL_NOSE_UP)
469 /* Detected an accel value outside -1.5g to 1.5g
470 * (or uncalibrated values), so we go into invalid mode
472 ao_flight_state = ao_flight_invalid;
476 if (!ao_flight_force_idle
478 && ao_ground_accel < ao_config.accel_plus_g + ACCEL_NOSE_UP
482 /* Set pad mode - we can fly! */
483 ao_flight_state = ao_flight_pad;
485 /* Disable the USB controller in flight mode
491 /* Disable packet mode in pad state */
492 ao_packet_slave_stop();
494 /* Turn on telemetry system */
496 ao_telemetry_set_interval(AO_TELEMETRY_INTERVAL_PAD);
498 /* signal successful initialization by turning off the LED */
499 ao_led_off(AO_LED_RED);
502 ao_flight_state = ao_flight_idle;
504 /* signal successful initialization by turning off the LED */
505 ao_led_off(AO_LED_RED);
507 /* wakeup threads due to state change */
508 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
515 * barometer: > 20m vertical motion
517 * accelerometer: > 2g AND velocity > 5m/s
519 * The accelerometer should always detect motion before
520 * the barometer, but we use both to make sure this
521 * transition is detected. If the device
522 * doesn't have an accelerometer, then ignore the
523 * speed and acceleration as they are quite noisy
526 if (ao_height > AO_M_TO_HEIGHT(20)
528 || (ao_accel > AO_MSS_TO_ACCEL(20) &&
529 ao_speed > AO_MS_TO_SPEED(5))
533 ao_flight_state = ao_flight_boost;
534 ao_launch_tick = ao_flight_tick;
536 /* start logging data */
539 /* Increase telemetry rate */
540 ao_telemetry_set_interval(AO_TELEMETRY_INTERVAL_FLIGHT);
542 /* disable RDF beacon */
546 /* Record current GPS position by waking up GPS log tasks */
547 ao_wakeup(&ao_gps_data);
548 ao_wakeup(&ao_gps_tracking_data);
551 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
555 case ao_flight_boost:
559 * accelerometer: start to fall at > 1/4 G
561 * time: boost for more than 15 seconds
563 * Detects motor burn out by the switch from acceleration to
564 * deceleration, or by waiting until the maximum burn duration
565 * (15 seconds) has past.
567 if ((ao_accel < AO_MSS_TO_ACCEL(-2.5) && ao_height > AO_M_TO_HEIGHT(100)) ||
568 (int16_t) (ao_flight_tick - ao_launch_tick) > BOOST_TICKS_MAX)
570 ao_flight_state = ao_flight_fast;
571 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
577 * This is essentially the same as coast,
578 * but the barometer is being ignored as
579 * it may be unreliable.
581 if (ao_speed < AO_MS_TO_SPEED(AO_MAX_BARO_SPEED)) {
582 ao_flight_state = ao_flight_coast;
583 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
587 case ao_flight_coast:
589 /* apogee detect: coast to drogue deploy:
593 * Also make sure the model altitude is tracking
594 * the measured altitude reasonably closely; otherwise
595 * we're probably transsonic.
597 if (ao_speed < 0 && (ao_raw_alt >= AO_MAX_BARO_HEIGHT || ao_error_h_sq_avg < 100))
599 /* ignite the drogue charge */
600 ao_ignite(ao_igniter_drogue);
602 /* slow down the telemetry system */
603 ao_telemetry_set_interval(AO_TELEMETRY_INTERVAL_RECOVER);
606 * Start recording min/max height
607 * to figure out when the rocket has landed
610 /* initialize interval values */
611 ao_interval_end = ao_flight_tick + AO_INTERVAL_TICKS;
613 ao_interval_min_height = ao_interval_max_height = ao_height;
615 /* and enter drogue state */
616 ao_flight_state = ao_flight_drogue;
617 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
621 case ao_flight_drogue:
623 /* drogue to main deploy:
625 * barometer: reach main deploy altitude
627 * Would like to use the accelerometer for this test, but
628 * the orientation of the flight computer is unknown after
629 * drogue deploy, so we ignore it. Could also detect
630 * high descent rate using the pressure sensor to
631 * recognize drogue deploy failure and eject the main
632 * at that point. Perhaps also use the drogue sense lines
633 * to notice continutity?
635 if (ao_height <= ao_config.main_deploy)
637 ao_ignite(ao_igniter_main);
638 ao_flight_state = ao_flight_main;
639 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
642 /* fall through... */
645 /* drogue/main to land:
647 * barometer: altitude stable and within 1000m of the launch altitude
650 if (ao_height < ao_interval_min_height)
651 ao_interval_min_height = ao_height;
652 if (ao_height > ao_interval_max_height)
653 ao_interval_max_height = ao_height;
655 if ((int16_t) (ao_flight_tick - ao_interval_end) >= 0) {
656 if (ao_height < AO_M_TO_HEIGHT(1000) &&
657 ao_interval_max_height - ao_interval_min_height < AO_M_TO_HEIGHT(5))
659 ao_flight_state = ao_flight_landed;
661 /* turn off the ADC capture */
662 ao_timer_set_adc_interval(0);
663 /* Enable RDF beacon */
666 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
668 ao_interval_min_height = ao_interval_max_height = ao_height;
669 ao_interval_end = ao_flight_tick + AO_INTERVAL_TICKS;
672 case ao_flight_landed:
678 static __xdata struct ao_task flight_task;
683 ao_flight_state = ao_flight_startup;
684 ao_add_task(&flight_task, ao_flight, "flight");