2 * Copyright © 2010 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; either version 2 of the License, or
7 * (at your option) any later version.
9 * This program is distributed in the hope that it will be useful, but
10 * WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * General Public License for more details.
14 * You should have received a copy of the GNU General Public License along
15 * with this program; if not, write to the Free Software Foundation, Inc.,
16 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
20 * Sensor data conversion functions
22 package org.altusmetrum.altoslib_12;
26 public class AltosConvert {
28 public static final double gravity = 9.80665;
31 * Pressure Sensor Model, version 1.1
33 * written by Holly Grimes
35 * Uses the International Standard Atmosphere as described in
36 * "A Quick Derivation relating altitude to air pressure" (version 1.03)
37 * from the Portland State Aerospace Society, except that the atmosphere
38 * is divided into layers with each layer having a different lapse rate.
40 * Lapse rate data for each layer was obtained from Wikipedia on Sept. 1, 2007
41 * at site <http://en.wikipedia.org/wiki/International_Standard_Atmosphere
43 * Height measurements use the local tangent plane. The postive z-direction is up.
45 * All measurements are given in SI units (Kelvin, Pascal, meter, meters/second^2).
46 * The lapse rate is given in Kelvin/meter, the gas constant for air is given
47 * in Joules/(kilogram-Kelvin).
50 private static final double GRAVITATIONAL_ACCELERATION = -gravity;
51 private static final double AIR_GAS_CONSTANT = 287.053;
52 private static final double NUMBER_OF_LAYERS = 7;
53 private static final double MAXIMUM_ALTITUDE = 84852.0;
54 private static final double MINIMUM_PRESSURE = 0.3734;
55 private static final double LAYER0_BASE_TEMPERATURE = 288.15;
56 private static final double LAYER0_BASE_PRESSURE = 101325;
58 /* lapse rate and base altitude for each layer in the atmosphere */
59 private static final double[] lapse_rate = {
60 -0.0065, 0.0, 0.001, 0.0028, 0.0, -0.0028, -0.002
63 private static final int[] base_altitude = {
64 0, 11000, 20000, 32000, 47000, 51000, 71000
67 /* outputs atmospheric pressure associated with the given altitude.
68 * altitudes are measured with respect to the mean sea level
71 altitude_to_pressure(double altitude)
73 double base_temperature = LAYER0_BASE_TEMPERATURE;
74 double base_pressure = LAYER0_BASE_PRESSURE;
77 double base; /* base for function to determine pressure */
78 double exponent; /* exponent for function to determine pressure */
79 int layer_number; /* identifies layer in the atmosphere */
80 double delta_z; /* difference between two altitudes */
82 if (altitude > MAXIMUM_ALTITUDE) /* FIX ME: use sensor data to improve model */
85 /* calculate the base temperature and pressure for the atmospheric layer
86 associated with the inputted altitude */
87 for(layer_number = 0; layer_number < NUMBER_OF_LAYERS - 1 && altitude > base_altitude[layer_number + 1]; layer_number++) {
88 delta_z = base_altitude[layer_number + 1] - base_altitude[layer_number];
89 if (lapse_rate[layer_number] == 0.0) {
90 exponent = GRAVITATIONAL_ACCELERATION * delta_z
91 / AIR_GAS_CONSTANT / base_temperature;
92 base_pressure *= Math.exp(exponent);
95 base = (lapse_rate[layer_number] * delta_z / base_temperature) + 1.0;
96 exponent = GRAVITATIONAL_ACCELERATION /
97 (AIR_GAS_CONSTANT * lapse_rate[layer_number]);
98 base_pressure *= Math.pow(base, exponent);
100 base_temperature += delta_z * lapse_rate[layer_number];
103 /* calculate the pressure at the inputted altitude */
104 delta_z = altitude - base_altitude[layer_number];
105 if (lapse_rate[layer_number] == 0.0) {
106 exponent = GRAVITATIONAL_ACCELERATION * delta_z
107 / AIR_GAS_CONSTANT / base_temperature;
108 pressure = base_pressure * Math.exp(exponent);
111 base = (lapse_rate[layer_number] * delta_z / base_temperature) + 1.0;
112 exponent = GRAVITATIONAL_ACCELERATION /
113 (AIR_GAS_CONSTANT * lapse_rate[layer_number]);
114 pressure = base_pressure * Math.pow(base, exponent);
121 /* outputs the altitude associated with the given pressure. the altitude
122 returned is measured with respect to the mean sea level */
124 pressure_to_altitude(double pressure)
127 double next_base_temperature = LAYER0_BASE_TEMPERATURE;
128 double next_base_pressure = LAYER0_BASE_PRESSURE;
131 double base_pressure;
132 double base_temperature;
133 double base; /* base for function to determine base pressure of next layer */
134 double exponent; /* exponent for function to determine base pressure
137 int layer_number; /* identifies layer in the atmosphere */
138 int delta_z; /* difference between two altitudes */
140 if (pressure < 0) /* illegal pressure */
142 if (pressure < MINIMUM_PRESSURE) /* FIX ME: use sensor data to improve model */
143 return MAXIMUM_ALTITUDE;
145 /* calculate the base temperature and pressure for the atmospheric layer
146 associated with the inputted pressure. */
150 base_pressure = next_base_pressure;
151 base_temperature = next_base_temperature;
152 delta_z = base_altitude[layer_number + 1] - base_altitude[layer_number];
153 if (lapse_rate[layer_number] == 0.0) {
154 exponent = GRAVITATIONAL_ACCELERATION * delta_z
155 / AIR_GAS_CONSTANT / base_temperature;
156 next_base_pressure *= Math.exp(exponent);
159 base = (lapse_rate[layer_number] * delta_z / base_temperature) + 1.0;
160 exponent = GRAVITATIONAL_ACCELERATION /
161 (AIR_GAS_CONSTANT * lapse_rate[layer_number]);
162 next_base_pressure *= Math.pow(base, exponent);
164 next_base_temperature += delta_z * lapse_rate[layer_number];
166 while(layer_number < NUMBER_OF_LAYERS - 1 && pressure < next_base_pressure);
168 /* calculate the altitude associated with the inputted pressure */
169 if (lapse_rate[layer_number] == 0.0) {
170 coefficient = (AIR_GAS_CONSTANT / GRAVITATIONAL_ACCELERATION)
172 altitude = base_altitude[layer_number]
173 + coefficient * Math.log(pressure / base_pressure);
176 base = pressure / base_pressure;
177 exponent = AIR_GAS_CONSTANT * lapse_rate[layer_number]
178 / GRAVITATIONAL_ACCELERATION;
179 coefficient = base_temperature / lapse_rate[layer_number];
180 altitude = base_altitude[layer_number]
181 + coefficient * (Math.pow(base, exponent) - 1);
187 public static double degrees_to_radians(double degrees) {
188 if (degrees == AltosLib.MISSING)
189 return AltosLib.MISSING;
190 return degrees * (Math.PI / 180.0);
193 public static double radians_to_degrees(double radians) {
194 if (radians == AltosLib.MISSING)
195 return AltosLib.MISSING;
196 return radians * (180.0 / Math.PI);
200 cc_battery_to_voltage(double battery)
202 return battery / 32767.0 * 5.0;
206 cc_igniter_to_voltage(double ignite)
208 return ignite / 32767 * 15.0;
212 barometer_to_pressure(double count)
214 return ((count / 16.0) / 2047.0 + 0.095) / 0.009 * 1000.0;
218 thermometer_to_temperature(double thermo)
220 return (thermo - 19791.268) / 32728.0 * 1.25 / 0.00247;
223 static double mega_adc(int raw) {
227 static public double mega_battery_voltage(int v_batt) {
228 if (v_batt != AltosLib.MISSING)
229 return 3.3 * mega_adc(v_batt) * (5.6 + 10.0) / 10.0;
230 return AltosLib.MISSING;
233 static double mega_pyro_voltage(int raw) {
234 if (raw != AltosLib.MISSING)
235 return 3.3 * mega_adc(raw) * (100.0 + 27.0) / 27.0;
236 return AltosLib.MISSING;
239 static double tele_mini_3_adc(int raw) {
243 static public double tele_mini_3_battery_voltage(int v_batt) {
244 if (v_batt != AltosLib.MISSING)
245 return 3.3 * tele_mini_3_adc(v_batt) * (5.6 + 10.0) / 10.0;
246 return AltosLib.MISSING;
249 static double tele_mini_3_pyro_voltage(int raw) {
250 if (raw != AltosLib.MISSING)
251 return 3.3 * tele_mini_3_adc(raw) * (100.0 + 27.0) / 27.0;
252 return AltosLib.MISSING;
255 static double tele_mini_2_voltage(int sensor) {
258 return sensor / 32767.0 * supply * 127/27;
261 static double tele_gps_voltage(int sensor) {
264 return sensor / 32767.0 * supply * (5.6 + 10.0) / 10.0;
267 static double tele_bt_3_battery(int raw) {
268 if (raw == AltosLib.MISSING)
269 return AltosLib.MISSING;
270 return 3.3 * mega_adc(raw) * (5.1 + 10.0) / 10.0;
273 static double easy_mini_2_adc(int raw) {
277 static double easy_mini_1_adc(int raw) {
278 return raw / 32767.0;
281 static double easy_mini_1_voltage(int sensor, int serial) {
283 double diode_offset = 0.0;
285 /* early prototypes had a 3.0V regulator */
289 /* Purple v1.0 boards had the sensor after the
290 * blocking diode, which drops about 150mV
293 diode_offset = 0.150;
295 return easy_mini_1_adc(sensor) * supply * 127/27 + diode_offset;
298 static double easy_mini_2_voltage(int sensor) {
301 return easy_mini_2_adc(sensor) * supply * 127/27;
304 public static double radio_to_frequency(int freq, int setting, int cal, int channel) {
312 f = 434.550 * setting / cal;
313 /* Round to nearest 50KHz */
314 f = Math.floor (20.0 * f + 0.5) / 20.0;
316 return f + channel * 0.100;
319 public static int radio_frequency_to_setting(double frequency, int cal) {
320 double set = frequency / 434.550 * cal;
322 return (int) Math.floor (set + 0.5);
325 public static int radio_frequency_to_channel(double frequency) {
326 int channel = (int) Math.floor ((frequency - 434.550) / 0.100 + 0.5);
335 public static double radio_channel_to_frequency(int channel) {
336 return 434.550 + channel * 0.100;
339 public static int telem_to_rssi(int telem) {
340 return telem / 2 - 74;
343 public static int[] ParseHex(String line) {
344 String[] tokens = line.split("\\s+");
345 int[] array = new int[tokens.length];
347 for (int i = 0; i < tokens.length; i++)
349 array[i] = Integer.parseInt(tokens[i], 16);
350 } catch (NumberFormatException ne) {
356 public static double meters_to_feet(double meters) {
357 return meters * (100 / (2.54 * 12));
360 public static double feet_to_meters(double feet) {
361 return feet * 12 * 2.54 / 100.0;
364 public static double meters_to_miles(double meters) {
365 return meters_to_feet(meters) / 5280;
368 public static double miles_to_meters(double miles) {
369 return feet_to_meters(miles * 5280);
372 public static double meters_to_mph(double mps) {
373 return meters_to_miles(mps) * 3600;
376 public static double mph_to_meters(double mps) {
377 return miles_to_meters(mps) / 3600;
380 public static double mps_to_fps(double mps) {
381 return meters_to_miles(mps) * 5280;
384 public static double fps_to_mps(double mps) {
385 return miles_to_meters(mps) / 5280;
388 public static double meters_to_mach(double meters) {
389 return meters / 343; /* something close to mach at usual rocket sites */
392 public static double meters_to_g(double meters) {
393 return meters / 9.80665;
396 public static double c_to_f(double c) {
400 public static double f_to_c(double c) {
401 return (c - 32) * 5/9;
404 public static double psi_to_pa(double psi) {
405 return psi * 6894.76;
408 public static double pa_to_psi(double pa) {
412 public static double n_to_lb(double n) {
413 return n * 0.22480894;
416 public static double lb_to_n(double lb) {
417 return lb / 0.22480894;
420 public static double acceleration_from_sensor(double sensor, double plus_g, double minus_g, double ground) {
422 if (sensor == AltosLib.MISSING)
423 return AltosLib.MISSING;
425 if (plus_g == AltosLib.MISSING || minus_g == AltosLib.MISSING)
426 return AltosLib.MISSING;
428 if (ground == AltosLib.MISSING)
431 double counts_per_g = (plus_g - minus_g) / 2.0;
432 double counts_per_mss = counts_per_g / gravity;
434 if (counts_per_mss == 0)
435 return AltosLib.MISSING;
437 return (sensor - ground) / counts_per_mss;
440 public static boolean imperial_units = false;
442 public static AltosDistance distance = new AltosDistance();
444 public static AltosHeight height = new AltosHeight();
446 public static AltosPressure pressure = new AltosPressure();
448 public static AltosForce force = new AltosForce();
450 public static AltosSpeed speed = new AltosSpeed();
452 public static AltosAccel accel = new AltosAccel();
454 public static AltosTemperature temperature = new AltosTemperature();
456 public static AltosOrient orient = new AltosOrient();
458 public static AltosVoltage voltage = new AltosVoltage();
460 public static AltosLatitude latitude = new AltosLatitude();
462 public static AltosLongitude longitude = new AltosLongitude();
464 public static AltosRotationRate rotation_rate = new AltosRotationRate();
466 public static AltosStateName state_name = new AltosStateName();
468 public static AltosPyroName pyro_name = new AltosPyroName();
470 public static AltosUnits magnetic_field = null;
472 public static String show_gs(String format, double a) {
474 format = format.concat(" g");
475 return String.format(format, a);
478 public static String say_gs(double a) {
479 return String.format("%6.0 gees", meters_to_g(a));
482 public static int checksum(int[] data, int start, int length) {
484 for (int i = 0; i < length; i++)
485 csum += data[i + start];
489 public static int checksum(List<Byte> data, int start, int length) {
491 for (int i = 0; i < length; i++)
492 csum += data.get(i+start);
496 public static double beep_value_to_freq(int value) {
499 return 1.0/2.0 * (24.0e6/32.0) / (double) value;
502 public static int beep_freq_to_value(double freq) {
505 return (int) Math.floor (1.0/2.0 * (24.0e6/32.0) / freq + 0.5);
508 public static final int BEARING_LONG = 0;
509 public static final int BEARING_SHORT = 1;
510 public static final int BEARING_VOICE = 2;
512 public static String bearing_to_words(int length, double bearing) {
513 String [][] bearing_string = {
515 "North", "North North East", "North East", "East North East",
516 "East", "East South East", "South East", "South South East",
517 "South", "South South West", "South West", "West South West",
518 "West", "West North West", "North West", "North North West"
520 "N", "NNE", "NE", "ENE",
521 "E", "ESE", "SE", "SSE",
522 "S", "SSW", "SW", "WSW",
523 "W", "WNW", "NW", "NNW"
525 "north", "nor nor east", "north east", "east nor east",
526 "east", "east sow east", "south east", "sow sow east",
527 "south", "sow sow west", "south west", "west sow west",
528 "west", "west nor west", "north west", "nor nor west "
531 return bearing_string[length][(int)((bearing / 90 * 8 + 1) / 2)%16];