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   1 /*
   2  * Copyright © 2009 Keith Packard <keithp@keithp.com>
   3  *
   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.
   7  *
   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.
  12  *
  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.
  16  */
  17
  18 #ifndef AO_FLIGHT_TEST
  19 #include "ao.h"
  20 #endif
  21
  22 #ifndef HAS_ACCEL
  23 #error Please define HAS_ACCEL
  24 #endif
  25
  26 #ifndef HAS_GPS
  27 #error Please define HAS_GPS
  28 #endif
  29
  30 #ifndef HAS_USB
  31 #error Please define HAS_USB
  32 #endif
  33
  34 /* Main flight thread. */
  35
  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 */
  41 #if HAS_ACCEL
  42 __pdata int16_t                 ao_ground_accel;        /* startup acceleration */
  43 #endif
  44
  45 /*
  46  * track min/max data over a long interval to detect
  47  * resting
  48  */
  49 __pdata uint16_t                ao_interval_end;
  50 __pdata int16_t                 ao_interval_min_height;
  51 __pdata int16_t                 ao_interval_max_height;
  52
  53 __data uint8_t ao_flight_adc;
  54 __pdata int16_t ao_raw_pres;
  55 __xdata uint8_t ao_flight_force_idle;
  56
  57 #if HAS_ACCEL
  58 __pdata int16_t ao_raw_accel, ao_raw_accel_prev;
  59 __pdata int16_t ao_accel_2g;
  60
  61 /* Accelerometer calibration
  62  *
  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:
  71  *
  72  * 26.67 mV/g * 32767/3300 counts/mV = 264.8 counts/g
  73  *
  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
  80  */
  81
  82 #define GRAVITY 9.80665
  83
  84 #define ACCEL_NOSE_UP   (ao_accel_2g >> 2)
  85
  86 #endif
  87
  88 /*
  89  * Barometer calibration
  90  *
  91  * We directly sample the barometer. The specs say:
  92  *
  93  * Pressure range: 15-115 kPa
  94  * Voltage at 115kPa: 2.82
  95  * Output scale: 27mV/kPa
  96  *
  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
 103  *
 104  * 27 mV/kPa * 32767 / 3300 counts/mV = 268.1 counts/kPa
 105  */
 106
 107 /* We also have a clock, which can be used to sanity check things in
 108  * case of other failures
 109  */
 110
 111 #define BOOST_TICKS_MAX AO_SEC_TO_TICKS(15)
 112
 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)
 116
 117 #include "ao_kalman.h"
 118
 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;
 124
 125 static __pdata int32_t          ao_k_height;
 126 static __pdata int32_t          ao_k_speed;
 127 static __pdata int32_t          ao_k_accel;
 128
 129 #define AO_K_STEP_100           to_fix16(0.01)
 130 #define AO_K_STEP_2_2_100       to_fix16(0.00005)
 131
 132 #define AO_K_STEP_10            to_fix16(0.1)
 133 #define AO_K_STEP_2_2_10        to_fix16(0.005)
 134
 135 /*
 136  * Above this height, the baro sensor doesn't work
 137  */
 138 #define AO_MAX_BARO_HEIGHT      12000
 139
 140 /*
 141  * Above this speed, baro measurements are unreliable
 142  */
 143 #define AO_MAX_BARO_SPEED       300
 144
 145 static void
 146 ao_kalman_predict(void)
 147 {
 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;
 153
 154                 return;
 155         }
 156 #endif
 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;
 160 }
 161
 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;
 166
 167 static void
 168 ao_kalman_err_height(void)
 169 {
 170         int16_t e;
 171         int16_t height_distrust;
 172 #if HAS_ACCEL
 173         int16_t speed_distrust;
 174 #endif
 175
 176         ao_error_h = ao_raw_height - (int16_t) (ao_k_height >> 16);
 177
 178         e = ao_error_h;
 179         if (e < 0)
 180                 e = -e;
 181         if (e > 127)
 182                 e = 127;
 183         ao_error_h_sq_avg -= ao_error_h_sq_avg >> 4;
 184         ao_error_h_sq_avg += (e * e) >> 4;
 185
 186         height_distrust = ao_raw_height - AO_MAX_BARO_HEIGHT;
 187 #ifdef AO_FLIGHT_TEST
 188         if (height_distrust > 0)
 189                 printf ("height_distrust %d\n", height_distrust);
 190 #endif
 191 #if HAS_ACCEL
 192         speed_distrust = (ao_speed - AO_MS_TO_SPEED(AO_MAX_BARO_SPEED)) >> 4;
 193 #ifdef AO_FLIGHT_TEST
 194         if (speed_distrust > 0)
 195                 printf ("speed distrust %d\n", speed_distrust);
 196 #endif
 197         if (speed_distrust <= 0)
 198                 speed_distrust = 0;
 199         else if (speed_distrust > height_distrust)
 200                 height_distrust = speed_distrust;
 201 #endif
 202         if (height_distrust <= 0)
 203                 height_distrust = 0;
 204
 205         if (height_distrust) {
 206                 if (height_distrust > 0x100)
 207                         height_distrust = 0x100;
 208                 ao_error_h = (int16_t) ((int32_t) ao_error_h * (0x100 - height_distrust)) >> 8;
 209         }
 210 }
 211
 212 static void
 213 ao_kalman_correct_baro(void)
 214 {
 215         ao_kalman_err_height();
 216 #ifdef AO_FLIGHT_TEST
 217         if (ao_flight_tick - ao_flight_prev_tick > 5) {
 218                 ao_k_height += (int32_t) AO_BARO_K0_10 * ao_error_h;
 219                 ao_k_speed  += (int32_t) AO_BARO_K1_10 * ao_error_h;
 220                 ao_k_accel  += (int32_t) AO_BARO_K2_10 * ao_error_h;
 221                 return;
 222         }
 223 #endif
 224         ao_k_height += (int32_t) AO_BARO_K0_100 * ao_error_h;
 225         ao_k_speed  += (int32_t) AO_BARO_K1_100 * ao_error_h;
 226         ao_k_accel  += (int32_t) AO_BARO_K2_100 * ao_error_h;
 227 }
 228
 229 #if HAS_ACCEL
 230 static __pdata int16_t ao_error_a;
 231 static __pdata int32_t ao_accel_scale;
 232
 233 static void
 234 ao_kalman_err_accel(void)
 235 {
 236         int32_t accel;
 237
 238         accel = (ao_ground_accel - ao_raw_accel) * ao_accel_scale;
 239
 240         /* Can't use ao_accel here as it is the pre-prediction value still */
 241         ao_error_a = (accel - ao_k_accel) >> 16;
 242 }
 243
 244 static void
 245 ao_kalman_correct_both(void)
 246 {
 247         ao_kalman_err_height();
 248         ao_kalman_err_accel();
 249
 250 #if 0
 251         /*
 252          * Check to see if things are crazy here --
 253          * if the computed height is far above the
 254          * measured height, we assume that the flight
 255          * trajectory is not vertical, and so ignore
 256          * the accelerometer for the remainder of the
 257          * flight.
 258          */
 259         if (ao_error_h_sq_avg > 10)
 260         {
 261                 ao_kalman_correct_baro();
 262                 return;
 263         }
 264 #endif
 265
 266 #ifdef AO_FLIGHT_TEST
 267         if (ao_flight_tick - ao_flight_prev_tick > 5) {
 268                 ao_k_height +=
 269                         (int32_t) AO_BOTH_K00_10 * ao_error_h +
 270                         (int32_t) (AO_BOTH_K01_10 >> 4) * ao_error_a;
 271                 ao_k_speed +=
 272                         ((int32_t) AO_BOTH_K10_10 << 4) * ao_error_h +
 273                         (int32_t) AO_BOTH_K11_10 * ao_error_a;
 274                 ao_k_accel +=
 275                         ((int32_t) AO_BOTH_K20_10 << 4) * ao_error_h +
 276                         (int32_t) AO_BOTH_K21_10 * ao_error_a;
 277                 return;
 278         }
 279 #endif
 280         ao_k_height +=
 281                 (int32_t) AO_BOTH_K00_100 * ao_error_h +
 282                 (int32_t) AO_BOTH_K01_100 * ao_error_a;
 283         ao_k_speed +=
 284                 (int32_t) AO_BOTH_K10_100 * ao_error_h +
 285                 (int32_t) AO_BOTH_K11_100 * ao_error_a;
 286         ao_k_accel +=
 287                 (int32_t) AO_BOTH_K20_100 * ao_error_h +
 288                 (int32_t) AO_BOTH_K21_100 * ao_error_a;
 289 }
 290
 291 static void
 292 ao_kalman_correct_accel(void)
 293 {
 294         ao_kalman_err_accel();
 295
 296 #ifdef AO_FLIGHT_TEST
 297         if (ao_flight_tick - ao_flight_prev_tick > 5) {
 298                 ao_k_height +=(int32_t) AO_ACCEL_K0_10 * ao_error_a;
 299                 ao_k_speed  += (int32_t) AO_ACCEL_K1_10 * ao_error_a;
 300                 ao_k_accel  += (int32_t) AO_ACCEL_K2_10 * ao_error_a;
 301                 return;
 302         }
 303 #endif
 304         ao_k_height += (int32_t) AO_ACCEL_K0_100 * ao_error_a;
 305         ao_k_speed  += (int32_t) AO_ACCEL_K1_100 * ao_error_a;
 306         ao_k_accel  += (int32_t) AO_ACCEL_K2_100 * ao_error_a;
 307 }
 308 #endif /* HAS_ACCEL */
 309
 310 __xdata int32_t ao_raw_pres_sum;
 311
 312 #ifdef HAS_ACCEL
 313 __xdata int32_t ao_raw_accel_sum;
 314 #endif
 315
 316 /* Landing is detected by getting constant readings from both pressure and accelerometer
 317  * for a fairly long time (AO_INTERVAL_TICKS)
 318  */
 319 #define AO_INTERVAL_TICKS       AO_SEC_TO_TICKS(5)
 320
 321 #define abs(a)  ((a) < 0 ? -(a) : (a))
 322
 323 void
 324 ao_flight(void)
 325 {
 326         __pdata static uint16_t nsamples = 0;
 327
 328         ao_flight_adc = ao_adc_head;
 329         ao_raw_pres = 0;
 330 #if HAS_ACCEL
 331         ao_raw_accel_prev = 0;
 332         ao_raw_accel = 0;
 333 #endif
 334         ao_flight_tick = 0;
 335         for (;;) {
 336                 ao_wakeup(DATA_TO_XDATA(&ao_flight_adc));
 337                 ao_sleep(DATA_TO_XDATA(&ao_adc_head));
 338                 while (ao_flight_adc != ao_adc_head) {
 339                         __xdata struct ao_adc *ao_adc;
 340                         ao_flight_prev_tick = ao_flight_tick;
 341
 342                         /* Capture a sample */
 343                         ao_adc = &ao_adc_ring[ao_flight_adc];
 344                         ao_flight_tick = ao_adc->tick;
 345                         ao_raw_pres = ao_adc->pres;
 346                         ao_raw_alt = ao_pres_to_altitude(ao_raw_pres);
 347                         ao_raw_height = ao_raw_alt - ao_ground_height;
 348 #if HAS_ACCEL
 349                         ao_raw_accel = ao_adc->accel;
 350 #if HAS_ACCEL_REF
 351                         /*
 352                          * Ok, the math here is a bit tricky.
 353                          *
 354                          * ao_raw_accel:  ADC output for acceleration
 355                          * ao_accel_ref:  ADC output for the 5V reference.
 356                          * ao_cook_accel: Corrected acceleration value
 357                          * Vcc:           3.3V supply to the CC1111
 358                          * Vac:           5V supply to the accelerometer
 359                          * accel:         input voltage to accelerometer ADC pin
 360                          * ref:           input voltage to 5V reference ADC pin
 361                          *
 362                          *
 363                          * Measured acceleration is ratiometric to Vcc:
 364                          *
 365                          *     ao_raw_accel   accel
 366                          *     ------------ = -----
 367                          *        32767        Vcc
 368                          *
 369                          * Measured 5v reference is also ratiometric to Vcc:
 370                          *
 371                          *     ao_accel_ref    ref
 372                          *     ------------ = -----
 373                          *        32767        Vcc
 374                          *
 375                          *
 376                          *      ao_accel_ref = 32767 * (ref / Vcc)
 377                          *
 378                          * Acceleration is measured ratiometric to the 5V supply,
 379                          * so what we want is:
 380                          *
 381                          *      ao_cook_accel    accel
 382                          *      ------------- =  -----
 383                          *          32767         ref
 384                          *
 385                          *
 386                          *                      accel    Vcc
 387                          *                    = ----- *  ---
 388                          *                       Vcc     ref
 389                          *
 390                          *                      ao_raw_accel       32767
 391                          *                    = ------------ *  ------------
 392                          *                         32737        ao_accel_ref
 393                          *
 394                          * Multiply through by 32767:
 395                          *
 396                          *                      ao_raw_accel * 32767
 397                          *      ao_cook_accel = --------------------
 398                          *                          ao_accel_ref
 399                          *
 400                          * Now, the tricky part. Getting this to compile efficiently
 401                          * and keeping all of the values in-range.
 402                          *
 403                          * First off, we need to use a shift of 16 instead of * 32767 as SDCC
 404                          * does the obvious optimizations for byte-granularity shifts:
 405                          *
 406                          *      ao_cook_accel = (ao_raw_accel << 16) / ao_accel_ref
 407                          *
 408                          * Next, lets check our input ranges:
 409                          *
 410                          *      0 <= ao_raw_accel <= 0x7fff             (singled ended ADC conversion)
 411                          *      0x7000 <= ao_accel_ref <= 0x7fff        (the 5V ref value is close to 0x7fff)
 412                          *
 413                          * Plugging in our input ranges, we get an output range of 0 - 0x12490,
 414                          * which is 17 bits. That won't work. If we take the accel ref and shift
 415                          * by a bit, we'll change its range:
 416                          *
 417                          *      0xe000 <= ao_accel_ref<<1 <= 0xfffe
 418                          *
 419                          *      ao_cook_accel = (ao_raw_accel << 16) / (ao_accel_ref << 1)
 420                          *
 421                          * Now the output range is 0 - 0x9248, which nicely fits in 16 bits. It
 422                          * is, however, one bit too large for our signed computations. So, we
 423                          * take the result and shift that by a bit:
 424                          *
 425                          *      ao_cook_accel = ((ao_raw_accel << 16) / (ao_accel_ref << 1)) >> 1
 426                          *
 427                          * This finally creates an output range of 0 - 0x4924. As the ADC only
 428                          * provides 11 bits of data, we haven't actually lost any precision,
 429                          * just dropped a bit of noise off the low end.
 430                          */
 431                         ao_raw_accel = (uint16_t) ((((uint32_t) ao_raw_accel << 16) / (ao_accel_ref[ao_flight_adc] << 1))) >> 1;
 432                         ao_adc->accel = ao_raw_accel;
 433 #endif
 434 #endif
 435
 436                         if (ao_flight_state > ao_flight_idle) {
 437                                 ao_kalman_predict();
 438 #if HAS_ACCEL
 439                                 if (ao_flight_state <= ao_flight_coast) {
 440 #ifdef FORCE_ACCEL
 441                                         ao_kalman_correct_accel();
 442 #else
 443                                         ao_kalman_correct_both();
 444 #endif
 445                                 } else
 446 #endif
 447                                         ao_kalman_correct_baro();
 448                                 ao_height = from_fix(ao_k_height);
 449                                 ao_speed = from_fix(ao_k_speed);
 450                                 ao_accel = from_fix(ao_k_accel);
 451                                 if (ao_height > ao_max_height)
 452                                         ao_max_height = ao_height;
 453                         }
 454                         ao_flight_adc = ao_adc_ring_next(ao_flight_adc);
 455                 }
 456
 457                 switch (ao_flight_state) {
 458                 case ao_flight_startup:
 459
 460                         /* startup state:
 461                          *
 462                          * Collect 512 samples of acceleration and pressure
 463                          * data and average them to find the resting values
 464                          */
 465                         if (nsamples < 512) {
 466 #if HAS_ACCEL
 467                                 ao_raw_accel_sum += ao_raw_accel;
 468 #endif
 469                                 ao_raw_pres_sum += ao_raw_pres;
 470                                 ++nsamples;
 471                                 continue;
 472                         }
 473                         ao_config_get();
 474 #if HAS_ACCEL
 475                         ao_ground_accel = ao_raw_accel_sum >> 9;
 476                         ao_accel_2g = ao_config.accel_minus_g - ao_config.accel_plus_g;
 477                         ao_accel_scale = to_fix32(GRAVITY * 2 * 16) / ao_accel_2g;
 478 #endif
 479                         ao_ground_pres = ao_raw_pres_sum >> 9;
 480                         ao_ground_height = ao_pres_to_altitude(ao_ground_pres);
 481
 482                         /* Check to see what mode we should go to.
 483                          *  - Invalid mode if accel cal appears to be out
 484                          *  - pad mode if we're upright,
 485                          *  - idle mode otherwise
 486                          */
 487 #if HAS_ACCEL
 488                         if (ao_config.accel_plus_g == 0 ||
 489                             ao_config.accel_minus_g == 0 ||
 490                             ao_ground_accel < ao_config.accel_plus_g - ACCEL_NOSE_UP ||
 491                             ao_ground_accel > ao_config.accel_minus_g + ACCEL_NOSE_UP)
 492                         {
 493                                 /* Detected an accel value outside -1.5g to 1.5g
 494                                  * (or uncalibrated values), so we go into invalid mode
 495                                  */
 496                                 ao_flight_state = ao_flight_invalid;
 497
 498                         } else
 499 #endif
 500                                 if (!ao_flight_force_idle
 501 #if HAS_ACCEL
 502                                     && ao_ground_accel < ao_config.accel_plus_g + ACCEL_NOSE_UP
 503 #endif
 504                                         )
 505                         {
 506                                 /* Set pad mode - we can fly! */
 507                                 ao_flight_state = ao_flight_pad;
 508 #if HAS_USB
 509                                 /* Disable the USB controller in flight mode
 510                                  * to save power
 511                                  */
 512                                 ao_usb_disable();
 513 #endif
 514
 515                                 /* Disable packet mode in pad state */
 516                                 ao_packet_slave_stop();
 517
 518                                 /* Turn on telemetry system */
 519                                 ao_rdf_set(1);
 520                                 ao_telemetry_set_interval(AO_TELEMETRY_INTERVAL_PAD);
 521
 522                                 /* signal successful initialization by turning off the LED */
 523                                 ao_led_off(AO_LED_RED);
 524                         } else {
 525                                 /* Set idle mode */
 526                                 ao_flight_state = ao_flight_idle;
 527
 528                                 /* signal successful initialization by turning off the LED */
 529                                 ao_led_off(AO_LED_RED);
 530                         }
 531                         /* wakeup threads due to state change */
 532                         ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
 533
 534                         break;
 535                 case ao_flight_pad:
 536
 537                         /* pad to boost:
 538                          *
 539                          * barometer: > 20m vertical motion
 540                          *             OR
 541                          * accelerometer: > 2g AND velocity > 5m/s
 542                          *
 543                          * The accelerometer should always detect motion before
 544                          * the barometer, but we use both to make sure this
 545                          * transition is detected. If the device
 546                          * doesn't have an accelerometer, then ignore the
 547                          * speed and acceleration as they are quite noisy
 548                          * on the pad.
 549                          */
 550                         if (ao_height > AO_M_TO_HEIGHT(20)
 551 #if HAS_ACCEL
 552                             || (ao_accel > AO_MSS_TO_ACCEL(20) &&
 553                                 ao_speed > AO_MS_TO_SPEED(5))
 554 #endif
 555                                 )
 556                         {
 557                                 ao_flight_state = ao_flight_boost;
 558                                 ao_launch_tick = ao_flight_tick;
 559
 560                                 /* start logging data */
 561                                 ao_log_start();
 562
 563                                 /* Increase telemetry rate */
 564                                 ao_telemetry_set_interval(AO_TELEMETRY_INTERVAL_FLIGHT);
 565
 566                                 /* disable RDF beacon */
 567                                 ao_rdf_set(0);
 568
 569 #if HAS_GPS
 570                                 /* Record current GPS position by waking up GPS log tasks */
 571                                 ao_wakeup(&ao_gps_data);
 572                                 ao_wakeup(&ao_gps_tracking_data);
 573 #endif
 574
 575                                 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
 576                                 break;
 577                         }
 578                         break;
 579                 case ao_flight_boost:
 580
 581                         /* boost to fast:
 582                          *
 583                          * accelerometer: start to fall at > 1/4 G
 584                          *              OR
 585                          * time: boost for more than 15 seconds
 586                          *
 587                          * Detects motor burn out by the switch from acceleration to
 588                          * deceleration, or by waiting until the maximum burn duration
 589                          * (15 seconds) has past.
 590                          */
 591                         if ((ao_accel < AO_MSS_TO_ACCEL(-2.5) && ao_height > AO_M_TO_HEIGHT(100)) ||
 592                             (int16_t) (ao_flight_tick - ao_launch_tick) > BOOST_TICKS_MAX)
 593                         {
 594                                 ao_flight_state = ao_flight_fast;
 595                                 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
 596                                 break;
 597                         }
 598                         break;
 599                 case ao_flight_fast:
 600                         /*
 601                          * This is essentially the same as coast,
 602                          * but the barometer is being ignored as
 603                          * it may be unreliable.
 604                          */
 605                         if (ao_speed < AO_MS_TO_SPEED(AO_MAX_BARO_SPEED)) {
 606                                 ao_flight_state = ao_flight_coast;
 607                                 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
 608                                 break;
 609                         }
 610                         break;
 611                 case ao_flight_coast:
 612
 613                         /* apogee detect: coast to drogue deploy:
 614                          *
 615                          * speed: < 0
 616                          *
 617                          * Also make sure the model altitude is tracking
 618                          * the measured altitude reasonably closely; otherwise
 619                          * we're probably transsonic.
 620                          */
 621                         if (ao_speed < 0 && (ao_raw_alt >= AO_MAX_BARO_HEIGHT || ao_error_h_sq_avg < 100))
 622                         {
 623                                 /* ignite the drogue charge */
 624                                 ao_ignite(ao_igniter_drogue);
 625
 626                                 /* slow down the telemetry system */
 627                                 ao_telemetry_set_interval(AO_TELEMETRY_INTERVAL_RECOVER);
 628
 629                                 /*
 630                                  * Start recording min/max height
 631                                  * to figure out when the rocket has landed
 632                                  */
 633
 634                                 /* initialize interval values */
 635                                 ao_interval_end = ao_flight_tick + AO_INTERVAL_TICKS;
 636
 637                                 ao_interval_min_height = ao_interval_max_height = ao_height;
 638
 639                                 /* and enter drogue state */
 640                                 ao_flight_state = ao_flight_drogue;
 641                                 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
 642                         }
 643
 644                         break;
 645                 case ao_flight_drogue:
 646
 647                         /* drogue to main deploy:
 648                          *
 649                          * barometer: reach main deploy altitude
 650                          *
 651                          * Would like to use the accelerometer for this test, but
 652                          * the orientation of the flight computer is unknown after
 653                          * drogue deploy, so we ignore it. Could also detect
 654                          * high descent rate using the pressure sensor to
 655                          * recognize drogue deploy failure and eject the main
 656                          * at that point. Perhaps also use the drogue sense lines
 657                          * to notice continutity?
 658                          */
 659                         if (ao_height <= ao_config.main_deploy)
 660                         {
 661                                 ao_ignite(ao_igniter_main);
 662                                 ao_flight_state = ao_flight_main;
 663                                 ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
 664                         }
 665
 666                         /* fall through... */
 667                 case ao_flight_main:
 668
 669                         /* drogue/main to land:
 670                          *
 671                          * barometer: altitude stable and within 1000m of the launch altitude
 672                          */
 673
 674                         if (ao_height < ao_interval_min_height)
 675                                 ao_interval_min_height = ao_height;
 676                         if (ao_height > ao_interval_max_height)
 677                                 ao_interval_max_height = ao_height;
 678
 679                         if ((int16_t) (ao_flight_tick - ao_interval_end) >= 0) {
 680                                 if (ao_height < AO_M_TO_HEIGHT(1000) &&
 681                                     ao_interval_max_height - ao_interval_min_height < AO_M_TO_HEIGHT(5))
 682                                 {
 683                                         ao_flight_state = ao_flight_landed;
 684
 685                                         /* turn off the ADC capture */
 686                                         ao_timer_set_adc_interval(0);
 687                                         /* Enable RDF beacon */
 688                                         ao_rdf_set(1);
 689
 690                                         ao_wakeup(DATA_TO_XDATA(&ao_flight_state));
 691                                 }
 692                                 ao_interval_min_height = ao_interval_max_height = ao_height;
 693                                 ao_interval_end = ao_flight_tick + AO_INTERVAL_TICKS;
 694                         }
 695                         break;
 696                 case ao_flight_landed:
 697                         break;
 698                 }
 699         }
 700 }
 701
 702 static __xdata struct ao_task   flight_task;
 703
 704 void
 705 ao_flight_init(void)
 706 {
 707         ao_flight_state = ao_flight_startup;
 708         ao_add_task(&flight_task, ao_flight, "flight");
 709 }