/* * Copyright © 2009 Keith Packard * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; version 2 of the License. * * This program is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * General Public License for more details. * * You should have received a copy of the GNU General Public License along * with this program; if not, write to the Free Software Foundation, Inc., * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA. */ #ifndef AO_FLIGHT_TEST #include "ao.h" #endif /* Main flight thread. */ __pdata enum ao_flight_state ao_flight_state; /* current flight state */ __pdata uint16_t ao_flight_tick; /* time of last data */ __pdata uint16_t ao_flight_prev_tick; /* time of previous data */ __pdata int16_t ao_flight_accel; /* filtered acceleration */ __pdata int16_t ao_flight_pres; /* filtered pressure */ __pdata int16_t ao_ground_pres; /* startup pressure */ __pdata int16_t ao_ground_accel; /* startup acceleration */ __pdata int16_t ao_min_pres; /* minimum recorded pressure */ __pdata uint16_t ao_launch_tick; /* time of launch detect */ __pdata int16_t ao_main_pres; /* pressure to eject main */ /* * track min/max data over a long interval to detect * resting */ __pdata uint16_t ao_interval_end; __pdata int16_t ao_interval_cur_min_accel; __pdata int16_t ao_interval_cur_max_accel; __pdata int16_t ao_interval_cur_min_pres; __pdata int16_t ao_interval_cur_max_pres; __pdata int16_t ao_interval_min_accel; __pdata int16_t ao_interval_max_accel; __pdata int16_t ao_interval_min_pres; __pdata int16_t ao_interval_max_pres; __data uint8_t ao_flight_adc; __pdata int16_t ao_raw_accel, ao_raw_accel_prev, ao_raw_pres; /* Accelerometer calibration * * We're sampling the accelerometer through a resistor divider which * consists of 5k and 10k resistors. This multiplies the values by 2/3. * That goes into the cc1111 A/D converter, which is running at 11 bits * of precision with the bits in the MSB of the 16 bit value. Only positive * values are used, so values should range from 0-32752 for 0-3.3V. The * specs say we should see 40mV/g (uncalibrated), multiply by 2/3 for what * the A/D converter sees (26.67 mV/g). We should see 32752/3300 counts/mV, * for a final computation of: * * 26.67 mV/g * 32767/3300 counts/mV = 264.8 counts/g * * Zero g was measured at 16000 (we would expect 16384). * Note that this value is only require to tell if the * rocket is standing upright. Once that is determined, * the value of the accelerometer is averaged for 100 samples * to find the resting accelerometer value, which is used * for all further flight computations */ #define GRAVITY 9.80665 /* convert m/s to velocity count */ #define VEL_MPS_TO_COUNT(mps) ((int32_t) (((mps) / GRAVITY) * ACCEL_G * 100)) #define ACCEL_G 265 #define ACCEL_ZERO_G 16000 #define ACCEL_NOSE_UP (ACCEL_G * 2 /3) #define ACCEL_BOOST ACCEL_G * 2 #define ACCEL_INT_LAND (ACCEL_G / 10) #define ACCEL_VEL_LAND VEL_MPS_TO_COUNT(10) #define ACCEL_VEL_MACH VEL_MPS_TO_COUNT(200) #define ACCEL_VEL_APOGEE VEL_MPS_TO_COUNT(2) #define ACCEL_VEL_MAIN VEL_MPS_TO_COUNT(100) #define ACCEL_VEL_BOOST VEL_MPS_TO_COUNT(5) /* * Barometer calibration * * We directly sample the barometer. The specs say: * * Pressure range: 15-115 kPa * Voltage at 115kPa: 2.82 * Output scale: 27mV/kPa * * If we want to detect launch with the barometer, we need * a large enough bump to not be fooled by noise. At typical * launch elevations (0-2000m), a 200Pa pressure change cooresponds * to about a 20m elevation change. This is 5.4mV, or about 3LSB. * As all of our calculations are done in 16 bits, we'll actually see a change * of 16 times this though * * 27 mV/kPa * 32767 / 3300 counts/mV = 268.1 counts/kPa */ #define BARO_kPa 268 #define BARO_LAUNCH (BARO_kPa / 5) /* .2kPa, or about 20m */ #define BARO_APOGEE (BARO_kPa / 10) /* .1kPa, or about 10m */ #define BARO_COAST (BARO_kPa * 5) /* 5kpa, or about 500m */ #define BARO_MAIN (BARO_kPa) /* 1kPa, or about 100m */ #define BARO_INT_LAND (BARO_kPa / 20) /* .05kPa, or about 5m */ #define BARO_LAND (BARO_kPa * 10) /* 10kPa or about 1000m */ /* We also have a clock, which can be used to sanity check things in * case of other failures */ #define BOOST_TICKS_MAX AO_SEC_TO_TICKS(15) /* This value is scaled in a weird way. It's a running total of accelerometer * readings minus the ground accelerometer reading. That means it measures * velocity, and quite accurately too. As it gets updated 100 times a second, * it's scaled by 100 */ __pdata int32_t ao_flight_vel; __pdata int32_t ao_min_vel; __pdata int32_t ao_old_vel; __pdata int16_t ao_old_vel_tick; __xdata int32_t ao_raw_accel_sum, ao_raw_pres_sum; /* Landing is detected by getting constant readings from both pressure and accelerometer * for a fairly long time (AO_INTERVAL_TICKS) */ #define AO_INTERVAL_TICKS AO_SEC_TO_TICKS(20) #define abs(a) ((a) < 0 ? -(a) : (a)) void ao_flight(void) { __pdata static uint16_t nsamples = 0; ao_flight_adc = ao_adc_head; ao_raw_accel_prev = 0; ao_raw_accel = 0; ao_raw_pres = 0; ao_flight_tick = 0; for (;;) { ao_sleep(&ao_adc_ring); while (ao_flight_adc != ao_adc_head) { __pdata uint8_t ticks; __pdata int16_t ao_vel_change; ao_flight_prev_tick = ao_flight_tick; /* Capture a sample */ ao_raw_accel = ao_adc_ring[ao_flight_adc].accel; ao_raw_pres = ao_adc_ring[ao_flight_adc].pres; ao_flight_tick = ao_adc_ring[ao_flight_adc].tick; ao_flight_accel -= ao_flight_accel >> 4; ao_flight_accel += ao_raw_accel >> 4; ao_flight_pres -= ao_flight_pres >> 4; ao_flight_pres += ao_raw_pres >> 4; /* Update velocity * * The accelerometer is mounted so that * acceleration yields negative values * while deceleration yields positive values, * so subtract instead of add. */ ticks = ao_flight_tick - ao_flight_prev_tick; ao_vel_change = (((ao_raw_accel + ao_raw_accel_prev) >> 1) - ao_ground_accel); ao_raw_accel_prev = ao_raw_accel; /* one is a common interval */ if (ticks == 1) ao_flight_vel -= (int32_t) ao_vel_change; else ao_flight_vel -= (int32_t) ao_vel_change * (int32_t) ticks; ao_flight_adc = ao_adc_ring_next(ao_flight_adc); } if (ao_flight_pres < ao_min_pres) ao_min_pres = ao_flight_pres; if (ao_flight_vel >= 0) { if (ao_flight_vel < ao_min_vel) ao_min_vel = ao_flight_vel; } else { if (-ao_flight_vel < ao_min_vel) ao_min_vel = -ao_flight_vel; } switch (ao_flight_state) { case ao_flight_startup: /* startup state: * * Collect 1000 samples of acceleration and pressure * data and average them to find the resting values */ if (nsamples < 1000) { ao_raw_accel_sum += ao_raw_accel; ao_raw_pres_sum += ao_raw_pres; ++nsamples; continue; } ao_ground_accel = (ao_raw_accel_sum / nsamples); ao_ground_pres = (ao_raw_pres_sum / nsamples); ao_min_pres = ao_ground_pres; ao_config_get(); ao_main_pres = ao_altitude_to_pres(ao_pres_to_altitude(ao_ground_pres) + ao_config.main_deploy); ao_flight_vel = 0; ao_min_vel = 0; ao_old_vel = ao_flight_vel; ao_old_vel_tick = ao_flight_tick; /* Go to launchpad state if the nose is pointing up */ ao_config_get(); if (ao_flight_accel < ao_config.accel_zero_g - ACCEL_NOSE_UP) { /* Disable the USB controller in flight mode * to save power */ ao_usb_disable(); /* Turn on telemetry system */ ao_rdf_set(1); ao_telemetry_set_interval(AO_TELEMETRY_INTERVAL_PAD); ao_flight_state = ao_flight_launchpad; ao_wakeup(DATA_TO_XDATA(&ao_flight_state)); } else { ao_flight_state = ao_flight_idle; /* Turn on the Green LED in idle mode */ ao_led_on(AO_LED_GREEN); ao_wakeup(DATA_TO_XDATA(&ao_flight_state)); } /* signal successful initialization by turning off the LED */ ao_led_off(AO_LED_RED); break; case ao_flight_launchpad: /* Trim velocity * * Once a second, remove any velocity from * a second ago */ if ((int16_t) (ao_flight_tick - ao_old_vel_tick) >= AO_SEC_TO_TICKS(1)) { ao_old_vel_tick = ao_flight_tick; ao_flight_vel -= ao_old_vel; ao_old_vel = ao_flight_vel; } /* pad to boost: * * accelerometer: > 2g AND velocity > 5m/s * OR * barometer: > 20m vertical motion * * The accelerometer should always detect motion before * the barometer, but we use both to make sure this * transition is detected */ if ((ao_flight_accel < ao_ground_accel - ACCEL_BOOST && ao_flight_vel > ACCEL_VEL_BOOST) || ao_flight_pres < ao_ground_pres - BARO_LAUNCH) { ao_flight_state = ao_flight_boost; ao_launch_tick = ao_flight_tick; /* start logging data */ ao_log_start(); /* Increase telemetry rate */ ao_telemetry_set_interval(AO_TELEMETRY_INTERVAL_FLIGHT); /* disable RDF beacon */ ao_rdf_set(0); ao_wakeup(DATA_TO_XDATA(&ao_flight_state)); break; } break; case ao_flight_boost: /* boost to coast: * * accelerometer: start to fall at > 1/4 G * OR * time: boost for more than 15 seconds * * Detects motor burn out by the switch from acceleration to * deceleration, or by waiting until the maximum burn duration * (15 seconds) has past. */ if (ao_flight_accel > ao_ground_accel + (ACCEL_G >> 2) || (int16_t) (ao_flight_tick - ao_launch_tick) > BOOST_TICKS_MAX) { ao_flight_state = ao_flight_coast; ao_wakeup(DATA_TO_XDATA(&ao_flight_state)); break; } break; case ao_flight_coast: /* coast to apogee detect: * * accelerometer: integrated velocity < 200 m/s * OR * barometer: fall at least 500m from max altitude * * This extra state is required to avoid mis-detecting * apogee due to mach transitions. * * XXX this is essentially a single-detector test * as the 500m altitude change would likely result * in a loss of the rocket. More data on precisely * how big a pressure change the mach transition * generates would be useful here. */ if (ao_flight_vel < ACCEL_VEL_MACH || ao_flight_pres > ao_min_pres + BARO_COAST) { /* set min velocity to current velocity for * apogee detect */ ao_min_vel = abs(ao_flight_vel); ao_flight_state = ao_flight_apogee; ao_wakeup(DATA_TO_XDATA(&ao_flight_state)); } break; case ao_flight_apogee: /* apogee detect to drogue deploy: * * accelerometer: abs(velocity) > min_velocity + 2m/s * OR * barometer: fall at least 10m * * If the barometer saturates because the flight * goes over its measuring range (about 53k'), * requiring a 10m fall will avoid prematurely * detecting apogee; the accelerometer will take * over in that case and the integrated velocity * measurement should suffice to find apogee */ if (/* abs(ao_flight_vel) > ao_min_vel + ACCEL_VEL_APOGEE || */ ao_flight_pres > ao_min_pres + BARO_APOGEE) { /* ignite the drogue charge */ ao_ignite(ao_igniter_drogue); /* slow down the telemetry system */ ao_telemetry_set_interval(AO_TELEMETRY_INTERVAL_RECOVER); /* slow down the ADC sample rate */ ao_timer_set_adc_interval(10); /* Enable RDF beacon */ ao_rdf_set(1); /* * Start recording min/max accel and pres for a while * to figure out when the rocket has landed */ /* Set the 'last' limits to max range to prevent * early resting detection */ ao_interval_min_accel = 0; ao_interval_max_accel = 0x7fff; ao_interval_min_pres = 0; ao_interval_max_pres = 0x7fff; /* initialize interval values */ ao_interval_end = ao_flight_tick + AO_INTERVAL_TICKS; ao_interval_cur_min_pres = ao_interval_cur_max_pres = ao_flight_pres; ao_interval_cur_min_accel = ao_interval_cur_max_accel = ao_flight_accel; /* and enter drogue state */ ao_flight_state = ao_flight_drogue; ao_wakeup(DATA_TO_XDATA(&ao_flight_state)); } break; case ao_flight_drogue: /* drogue to main deploy: * * barometer: reach main deploy altitude * * Would like to use the accelerometer for this test, but * the orientation of the flight computer is unknown after * drogue deploy, so we ignore it. Could also detect * high descent rate using the pressure sensor to * recognize drogue deploy failure and eject the main * at that point. Perhaps also use the drogue sense lines * to notice continutity? */ if (ao_flight_pres >= ao_main_pres) { ao_ignite(ao_igniter_main); ao_flight_state = ao_flight_main; ao_wakeup(DATA_TO_XDATA(&ao_flight_state)); } /* fall through... */ case ao_flight_main: /* drogue/main to land: * * accelerometer: value stable * AND * barometer: altitude stable and within 1000m of the launch altitude */ if (ao_flight_pres < ao_interval_cur_min_pres) ao_interval_cur_min_pres = ao_flight_pres; if (ao_flight_pres > ao_interval_cur_max_pres) ao_interval_cur_max_pres = ao_flight_pres; if (ao_flight_accel < ao_interval_cur_min_accel) ao_interval_cur_min_accel = ao_flight_accel; if (ao_flight_accel > ao_interval_cur_max_accel) ao_interval_cur_max_accel = ao_flight_accel; if ((int16_t) (ao_flight_tick - ao_interval_end) >= 0) { ao_interval_max_pres = ao_interval_cur_max_pres; ao_interval_min_pres = ao_interval_cur_min_pres; ao_interval_max_accel = ao_interval_cur_max_accel; ao_interval_min_accel = ao_interval_cur_min_accel; ao_interval_end = ao_flight_tick + AO_INTERVAL_TICKS; ao_interval_cur_min_pres = ao_interval_cur_max_pres = ao_flight_pres; ao_interval_cur_min_accel = ao_interval_cur_max_accel = ao_flight_accel; } if ((uint16_t) (ao_interval_max_accel - ao_interval_min_accel) < (uint16_t) ACCEL_INT_LAND && ao_flight_pres > ao_ground_pres - BARO_LAND && (uint16_t) (ao_interval_max_pres - ao_interval_min_pres) < (uint16_t) BARO_INT_LAND) { ao_flight_state = ao_flight_landed; /* turn off the ADC capture */ ao_timer_set_adc_interval(0); ao_wakeup(DATA_TO_XDATA(&ao_flight_state)); } break; case ao_flight_landed: break; } } } #define AO_ACCEL_COUNT_TO_MSS(count) ((count) / 27) #define AO_VEL_COUNT_TO_MS(count) ((int16_t) ((count) / 2700)) static void ao_flight_status(void) { printf("STATE: %7s accel: %d speed: %d altitude: %d main: %d\n", ao_state_names[ao_flight_state], AO_ACCEL_COUNT_TO_MSS(ACCEL_ZERO_G - ao_flight_accel), AO_VEL_COUNT_TO_MS(ao_flight_vel), ao_pres_to_altitude(ao_flight_pres), ao_pres_to_altitude(ao_main_pres)); } static __xdata struct ao_task flight_task; __code struct ao_cmds ao_flight_cmds[] = { { 'f', ao_flight_status, "f Display current flight state" }, { 0, ao_flight_status, NULL } }; void ao_flight_init(void) { ao_flight_state = ao_flight_startup; ao_interval_min_accel = 0; ao_interval_max_accel = 0x7fff; ao_interval_min_pres = 0; ao_interval_max_pres = 0x7fff; ao_interval_end = AO_INTERVAL_TICKS; ao_add_task(&flight_task, ao_flight, "flight"); ao_cmd_register(&ao_flight_cmds[0]); }