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;
52 /* Accelerometer calibration
54 * We're sampling the accelerometer through a resistor divider which
55 * consists of 5k and 10k resistors. This multiplies the values by 2/3.
56 * That goes into the cc1111 A/D converter, which is running at 11 bits
57 * of precision with the bits in the MSB of the 16 bit value. Only positive
58 * values are used, so values should range from 0-32752 for 0-3.3V. The
59 * specs say we should see 40mV/g (uncalibrated), multiply by 2/3 for what
60 * the A/D converter sees (26.67 mV/g). We should see 32752/3300 counts/mV,
61 * for a final computation of:
63 * 26.67 mV/g * 32767/3300 counts/mV = 264.8 counts/g
65 * Zero g was measured at 16000 (we would expect 16384).
66 * Note that this value is only require to tell if the
67 * rocket is standing upright. Once that is determined,
68 * the value of the accelerometer is averaged for 100 samples
69 * to find the resting accelerometer value, which is used
70 * for all further flight computations
73 #define GRAVITY 9.80665
74 /* convert m/s to velocity count */
75 #define VEL_MPS_TO_COUNT(mps) ((int32_t) (((mps) / GRAVITY) * ACCEL_G * 100))
78 #define ACCEL_ZERO_G 16000
79 #define ACCEL_NOSE_UP (ACCEL_G * 2 /3)
80 #define ACCEL_BOOST ACCEL_G * 2
81 #define ACCEL_INT_LAND (ACCEL_G / 10)
82 #define ACCEL_VEL_LAND VEL_MPS_TO_COUNT(10)
83 #define ACCEL_VEL_MACH VEL_MPS_TO_COUNT(200)
84 #define ACCEL_VEL_APOGEE VEL_MPS_TO_COUNT(2)
85 #define ACCEL_VEL_MAIN VEL_MPS_TO_COUNT(100)
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 __xdata int32_t ao_raw_accel_sum, ao_raw_pres_sum;
129 /* Landing is detected by getting constant readings from both pressure and accelerometer
130 * for a fairly long time (AO_INTERVAL_TICKS)
132 #define AO_INTERVAL_TICKS AO_SEC_TO_TICKS(20)
134 #define abs(a) ((a) < 0 ? -(a) : (a))
139 __pdata static uint8_t nsamples = 0;
141 ao_flight_adc = ao_adc_head;
142 ao_raw_accel_prev = 0;
145 ao_interval_cur_min_pres = 0x7fff;
146 ao_interval_cur_max_pres = -0x7fff;
147 ao_interval_cur_min_accel = 0x7fff;
148 ao_interval_cur_max_accel = -0x7fff;
151 ao_sleep(&ao_adc_ring);
152 while (ao_flight_adc != ao_adc_head) {
153 __pdata uint8_t ticks;
154 __pdata int16_t ao_vel_change;
155 ao_flight_prev_tick = ao_flight_tick;
157 /* Capture a sample */
158 ao_raw_accel = ao_adc_ring[ao_flight_adc].accel;
159 ao_raw_pres = ao_adc_ring[ao_flight_adc].pres;
160 ao_flight_tick = ao_adc_ring[ao_flight_adc].tick;
164 * The accelerometer is mounted so that
165 * acceleration yields negative values
166 * while deceleration yields positive values,
167 * so subtract instead of add.
169 ticks = ao_flight_tick - ao_flight_prev_tick;
170 ao_vel_change = (((ao_raw_accel + ao_raw_accel_prev) >> 1) - ao_ground_accel);
171 ao_raw_accel_prev = ao_raw_accel;
173 /* one is a common interval */
175 ao_flight_vel -= (int32_t) ao_vel_change;
177 ao_flight_vel -= (int32_t) ao_vel_change * (int32_t) ticks;
179 ao_flight_adc = ao_adc_ring_next(ao_flight_adc);
181 ao_flight_accel -= ao_flight_accel >> 4;
182 ao_flight_accel += ao_raw_accel >> 4;
183 ao_flight_pres -= ao_flight_pres >> 4;
184 ao_flight_pres += ao_raw_pres >> 4;
186 if (ao_flight_pres < ao_min_pres)
187 ao_min_pres = ao_flight_pres;
188 if (ao_flight_vel >= 0) {
189 if (ao_flight_vel < ao_min_vel)
190 ao_min_vel = ao_flight_vel;
192 if (-ao_flight_vel < ao_min_vel)
193 ao_min_vel = -ao_flight_vel;
196 if (ao_flight_pres < ao_interval_cur_min_pres)
197 ao_interval_cur_min_pres = ao_flight_pres;
198 if (ao_flight_pres > ao_interval_cur_max_pres)
199 ao_interval_cur_max_pres = ao_flight_pres;
200 if (ao_flight_accel < ao_interval_cur_min_accel)
201 ao_interval_cur_min_accel = ao_flight_accel;
202 if (ao_flight_accel > ao_interval_cur_max_accel)
203 ao_interval_cur_max_accel = ao_flight_accel;
205 if ((int16_t) (ao_flight_tick - ao_interval_end) >= 0) {
206 ao_interval_max_pres = ao_interval_cur_max_pres;
207 ao_interval_min_pres = ao_interval_cur_min_pres;
208 ao_interval_max_accel = ao_interval_cur_max_accel;
209 ao_interval_min_accel = ao_interval_cur_min_accel;
210 ao_interval_end = ao_flight_tick + AO_INTERVAL_TICKS;
211 ao_interval_cur_min_pres = ao_interval_cur_max_pres = ao_flight_pres;
212 ao_interval_cur_min_accel = ao_interval_cur_max_accel = ao_flight_accel;
215 switch (ao_flight_state) {
216 case ao_flight_startup:
220 * Collect 100 samples of acceleration and pressure
221 * data and average them to find the resting values
223 if (nsamples < 100) {
224 ao_raw_accel_sum += ao_raw_accel;
225 ao_raw_pres_sum += ao_raw_pres;
229 ao_ground_accel = (ao_raw_accel_sum / nsamples);
230 ao_ground_pres = (ao_raw_pres_sum / nsamples);
231 ao_min_pres = ao_ground_pres;
233 ao_main_pres = ao_altitude_to_pres(ao_pres_to_altitude(ao_ground_pres) + ao_config.main_deploy);
237 ao_interval_end = ao_flight_tick;
239 /* Go to launchpad state if the nose is pointing up */
241 if (ao_flight_accel < ao_config.accel_zero_g - ACCEL_NOSE_UP) {
243 /* Disable the USB controller in flight mode
248 /* Turn on telemetry system
251 ao_telemetry_set_interval(AO_TELEMETRY_INTERVAL_FLIGHT);
253 ao_flight_state = ao_flight_launchpad;
254 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
256 ao_flight_state = ao_flight_idle;
258 /* Turn on the Green LED in idle mode
260 ao_led_on(AO_LED_GREEN);
261 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
263 /* signal successful initialization by turning off the LED */
264 ao_led_off(AO_LED_RED);
266 case ao_flight_launchpad:
270 * accelerometer: > 2g
272 * barometer: > 20m vertical motion
274 * The accelerometer should always detect motion before
275 * the barometer, but we use both to make sure this
276 * transition is detected
278 if (ao_flight_accel < ao_ground_accel - ACCEL_BOOST ||
279 ao_flight_pres < ao_ground_pres - BARO_LAUNCH)
281 ao_flight_state = ao_flight_boost;
282 ao_launch_tick = ao_flight_tick;
284 /* start logging data */
287 /* disable RDF beacon */
290 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
294 case ao_flight_boost:
298 * accelerometer: start to fall at > 1/4 G
300 * time: boost for more than 15 seconds
302 * Detects motor burn out by the switch from acceleration to
303 * deceleration, or by waiting until the maximum burn duration
304 * (15 seconds) has past.
306 if (ao_flight_accel > ao_ground_accel + (ACCEL_G >> 2) ||
307 (int16_t) (ao_flight_tick - ao_launch_tick) > BOOST_TICKS_MAX)
309 ao_flight_state = ao_flight_coast;
310 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
314 case ao_flight_coast:
316 /* coast to apogee detect:
318 * accelerometer: integrated velocity < 200 m/s
320 * barometer: fall at least 500m from max altitude
322 * This extra state is required to avoid mis-detecting
323 * apogee due to mach transitions.
325 * XXX this is essentially a single-detector test
326 * as the 500m altitude change would likely result
327 * in a loss of the rocket. More data on precisely
328 * how big a pressure change the mach transition
329 * generates would be useful here.
331 if (ao_flight_vel < ACCEL_VEL_MACH ||
332 ao_flight_pres > ao_min_pres + BARO_COAST)
334 /* set min velocity to current velocity for
337 ao_min_vel = ao_flight_vel;
338 ao_flight_state = ao_flight_apogee;
339 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
342 case ao_flight_apogee:
344 /* apogee detect to drogue deploy:
346 * accelerometer: abs(velocity) > min_velocity + 2m/s
348 * barometer: fall at least 10m
350 * If the barometer saturates because the flight
351 * goes over its measuring range (about 53k'),
352 * requiring a 10m fall will avoid prematurely
353 * detecting apogee; the accelerometer will take
354 * over in that case and the integrated velocity
355 * measurement should suffice to find apogee
357 if (abs(ao_flight_vel) > ao_min_vel + ACCEL_VEL_APOGEE ||
358 ao_flight_pres > ao_min_pres + BARO_APOGEE)
360 /* ignite the drogue charge */
361 ao_ignite(ao_igniter_drogue);
363 /* slow down the telemetry system */
364 ao_telemetry_set_interval(AO_TELEMETRY_INTERVAL_RECOVER);
366 /* slow down the ADC sample rate */
367 ao_timer_set_adc_interval(10);
369 /* Enable RDF beacon */
372 ao_flight_state = ao_flight_drogue;
373 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
376 case ao_flight_drogue:
378 /* drogue to main deploy:
380 * accelerometer: abs(velocity) > 100m/s (in case the drogue failed)
382 * barometer: reach main deploy altitude
384 if (ao_flight_vel < -ACCEL_VEL_MAIN ||
385 ao_flight_vel > ACCEL_VEL_MAIN ||
386 ao_flight_pres >= ao_main_pres)
388 ao_ignite(ao_igniter_main);
389 ao_flight_state = ao_flight_main;
390 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
392 /* fall through... */
395 /* drogue/main to land:
397 * accelerometer: value stable and velocity less than 10m/s
399 * barometer: altitude stable and within 1000m of the launch altitude
401 if ((abs(ao_flight_vel) < ACCEL_VEL_LAND &&
402 (ao_interval_max_accel - ao_interval_min_accel) < ACCEL_INT_LAND) ||
403 (ao_flight_pres > ao_ground_pres - BARO_LAND &&
404 (ao_interval_max_pres - ao_interval_min_pres) < BARO_INT_LAND))
406 ao_flight_state = ao_flight_landed;
408 /* turn off the ADC capture */
409 ao_timer_set_adc_interval(0);
411 /* stop logging data */
414 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
417 case ao_flight_landed:
423 #define AO_ACCEL_COUNT_TO_MSS(count) ((count) / 27)
424 #define AO_VEL_COUNT_TO_MS(count) ((int16_t) ((count) / 2700))
427 ao_flight_status(void)
429 printf("STATE: %7s accel: %d speed: %d altitude: %d main: %d\n",
430 ao_state_names[ao_flight_state],
431 AO_ACCEL_COUNT_TO_MSS(ACCEL_ZERO_G - ao_flight_accel),
432 AO_VEL_COUNT_TO_MS(ao_flight_vel),
433 ao_pres_to_altitude(ao_flight_pres),
434 ao_pres_to_altitude(ao_main_pres));
437 static __xdata struct ao_task flight_task;
439 __code struct ao_cmds ao_flight_cmds[] = {
440 { 'f', ao_flight_status, "f Display current flight state" },
441 { 0, ao_flight_status, NULL }
447 ao_flight_state = ao_flight_startup;
448 ao_interval_min_accel = 0;
449 ao_interval_max_accel = 0x7fff;
450 ao_interval_min_pres = 0;
451 ao_interval_max_pres = 0x7fff;
452 ao_interval_end = AO_INTERVAL_TICKS;
454 ao_add_task(&flight_task, ao_flight, "flight");
455 ao_cmd_register(&ao_flight_cmds[0]);