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; 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.
19 * Sensor data conversion functions
21 package org.altusmetrum.altoslib_4;
23 public class AltosConvert {
25 * Pressure Sensor Model, version 1.1
27 * written by Holly Grimes
29 * Uses the International Standard Atmosphere as described in
30 * "A Quick Derivation relating altitude to air pressure" (version 1.03)
31 * from the Portland State Aerospace Society, except that the atmosphere
32 * is divided into layers with each layer having a different lapse rate.
34 * Lapse rate data for each layer was obtained from Wikipedia on Sept. 1, 2007
35 * at site <http://en.wikipedia.org/wiki/International_Standard_Atmosphere
37 * Height measurements use the local tangent plane. The postive z-direction is up.
39 * All measurements are given in SI units (Kelvin, Pascal, meter, meters/second^2).
40 * The lapse rate is given in Kelvin/meter, the gas constant for air is given
41 * in Joules/(kilogram-Kelvin).
44 public static final double GRAVITATIONAL_ACCELERATION = -9.80665;
45 public static final double AIR_GAS_CONSTANT = 287.053;
46 public static final double NUMBER_OF_LAYERS = 7;
47 public static final double MAXIMUM_ALTITUDE = 84852.0;
48 public static final double MINIMUM_PRESSURE = 0.3734;
49 public static final double LAYER0_BASE_TEMPERATURE = 288.15;
50 public static final double LAYER0_BASE_PRESSURE = 101325;
52 /* lapse rate and base altitude for each layer in the atmosphere */
53 public static final double[] lapse_rate = {
54 -0.0065, 0.0, 0.001, 0.0028, 0.0, -0.0028, -0.002
57 public static final int[] base_altitude = {
58 0, 11000, 20000, 32000, 47000, 51000, 71000
61 /* outputs atmospheric pressure associated with the given altitude.
62 * altitudes are measured with respect to the mean sea level
65 altitude_to_pressure(double altitude)
67 double base_temperature = LAYER0_BASE_TEMPERATURE;
68 double base_pressure = LAYER0_BASE_PRESSURE;
71 double base; /* base for function to determine pressure */
72 double exponent; /* exponent for function to determine pressure */
73 int layer_number; /* identifies layer in the atmosphere */
74 double delta_z; /* difference between two altitudes */
76 if (altitude > MAXIMUM_ALTITUDE) /* FIX ME: use sensor data to improve model */
79 /* calculate the base temperature and pressure for the atmospheric layer
80 associated with the inputted altitude */
81 for(layer_number = 0; layer_number < NUMBER_OF_LAYERS - 1 && altitude > base_altitude[layer_number + 1]; layer_number++) {
82 delta_z = base_altitude[layer_number + 1] - base_altitude[layer_number];
83 if (lapse_rate[layer_number] == 0.0) {
84 exponent = GRAVITATIONAL_ACCELERATION * delta_z
85 / AIR_GAS_CONSTANT / base_temperature;
86 base_pressure *= Math.exp(exponent);
89 base = (lapse_rate[layer_number] * delta_z / base_temperature) + 1.0;
90 exponent = GRAVITATIONAL_ACCELERATION /
91 (AIR_GAS_CONSTANT * lapse_rate[layer_number]);
92 base_pressure *= Math.pow(base, exponent);
94 base_temperature += delta_z * lapse_rate[layer_number];
97 /* calculate the pressure at the inputted altitude */
98 delta_z = altitude - base_altitude[layer_number];
99 if (lapse_rate[layer_number] == 0.0) {
100 exponent = GRAVITATIONAL_ACCELERATION * delta_z
101 / AIR_GAS_CONSTANT / base_temperature;
102 pressure = base_pressure * Math.exp(exponent);
105 base = (lapse_rate[layer_number] * delta_z / base_temperature) + 1.0;
106 exponent = GRAVITATIONAL_ACCELERATION /
107 (AIR_GAS_CONSTANT * lapse_rate[layer_number]);
108 pressure = base_pressure * Math.pow(base, exponent);
115 /* outputs the altitude associated with the given pressure. the altitude
116 returned is measured with respect to the mean sea level */
118 pressure_to_altitude(double pressure)
121 double next_base_temperature = LAYER0_BASE_TEMPERATURE;
122 double next_base_pressure = LAYER0_BASE_PRESSURE;
125 double base_pressure;
126 double base_temperature;
127 double base; /* base for function to determine base pressure of next layer */
128 double exponent; /* exponent for function to determine base pressure
131 int layer_number; /* identifies layer in the atmosphere */
132 int delta_z; /* difference between two altitudes */
134 if (pressure < 0) /* illegal pressure */
136 if (pressure < MINIMUM_PRESSURE) /* FIX ME: use sensor data to improve model */
137 return MAXIMUM_ALTITUDE;
139 /* calculate the base temperature and pressure for the atmospheric layer
140 associated with the inputted pressure. */
144 base_pressure = next_base_pressure;
145 base_temperature = next_base_temperature;
146 delta_z = base_altitude[layer_number + 1] - base_altitude[layer_number];
147 if (lapse_rate[layer_number] == 0.0) {
148 exponent = GRAVITATIONAL_ACCELERATION * delta_z
149 / AIR_GAS_CONSTANT / base_temperature;
150 next_base_pressure *= Math.exp(exponent);
153 base = (lapse_rate[layer_number] * delta_z / base_temperature) + 1.0;
154 exponent = GRAVITATIONAL_ACCELERATION /
155 (AIR_GAS_CONSTANT * lapse_rate[layer_number]);
156 next_base_pressure *= Math.pow(base, exponent);
158 next_base_temperature += delta_z * lapse_rate[layer_number];
160 while(layer_number < NUMBER_OF_LAYERS - 1 && pressure < next_base_pressure);
162 /* calculate the altitude associated with the inputted pressure */
163 if (lapse_rate[layer_number] == 0.0) {
164 coefficient = (AIR_GAS_CONSTANT / GRAVITATIONAL_ACCELERATION)
166 altitude = base_altitude[layer_number]
167 + coefficient * Math.log(pressure / base_pressure);
170 base = pressure / base_pressure;
171 exponent = AIR_GAS_CONSTANT * lapse_rate[layer_number]
172 / GRAVITATIONAL_ACCELERATION;
173 coefficient = base_temperature / lapse_rate[layer_number];
174 altitude = base_altitude[layer_number]
175 + coefficient * (Math.pow(base, exponent) - 1);
182 cc_battery_to_voltage(double battery)
184 return battery / 32767.0 * 5.0;
188 cc_ignitor_to_voltage(double ignite)
190 return ignite / 32767 * 15.0;
194 barometer_to_pressure(double count)
196 return ((count / 16.0) / 2047.0 + 0.095) / 0.009 * 1000.0;
200 thermometer_to_temperature(double thermo)
202 return (thermo - 19791.268) / 32728.0 * 1.25 / 0.00247;
205 static double mega_adc(int raw) {
209 static public double mega_battery_voltage(int v_batt) {
210 if (v_batt != AltosLib.MISSING)
211 return 3.3 * mega_adc(v_batt) * (15.0 + 27.0) / 27.0;
212 return AltosLib.MISSING;
215 static double mega_pyro_voltage(int raw) {
216 if (raw != AltosLib.MISSING)
217 return 3.3 * mega_adc(raw) * (100.0 + 27.0) / 27.0;
218 return AltosLib.MISSING;
221 static double tele_mini_voltage(int sensor) {
224 return sensor / 32767.0 * supply * 127/27;
227 static double easy_mini_voltage(int sensor, int serial) {
229 double diode_offset = 0.0;
231 /* early prototypes had a 3.0V regulator */
235 /* Purple v1.0 boards had the sensor after the
236 * blocking diode, which drops about 150mV
239 diode_offset = 0.150;
241 return sensor / 32767.0 * supply * 127/27 + diode_offset;
244 public static double radio_to_frequency(int freq, int setting, int cal, int channel) {
252 f = 434.550 * setting / cal;
253 /* Round to nearest 50KHz */
254 f = Math.floor (20.0 * f + 0.5) / 20.0;
256 return f + channel * 0.100;
259 public static int radio_frequency_to_setting(double frequency, int cal) {
260 double set = frequency / 434.550 * cal;
262 return (int) Math.floor (set + 0.5);
265 public static int radio_frequency_to_channel(double frequency) {
266 int channel = (int) Math.floor ((frequency - 434.550) / 0.100 + 0.5);
275 public static double radio_channel_to_frequency(int channel) {
276 return 434.550 + channel * 0.100;
279 public static int[] ParseHex(String line) {
280 String[] tokens = line.split("\\s+");
281 int[] array = new int[tokens.length];
283 for (int i = 0; i < tokens.length; i++)
285 array[i] = Integer.parseInt(tokens[i], 16);
286 } catch (NumberFormatException ne) {
292 public static double meters_to_feet(double meters) {
293 return meters * (100 / (2.54 * 12));
296 public static double feet_to_meters(double feet) {
297 return feet * 12 * 2.54 / 100.0;
300 public static double meters_to_miles(double meters) {
301 return meters_to_feet(meters) / 5280;
304 public static double miles_to_meters(double miles) {
305 return feet_to_meters(miles * 5280);
308 public static double meters_to_mph(double mps) {
309 return meters_to_miles(mps) * 3600;
312 public static double mph_to_meters(double mps) {
313 return miles_to_meters(mps) / 3600;
316 public static double meters_to_mach(double meters) {
317 return meters / 343; /* something close to mach at usual rocket sites */
320 public static double meters_to_g(double meters) {
321 return meters / 9.80665;
324 public static double c_to_f(double c) {
328 public static double f_to_c(double c) {
329 return (c - 32) * 5/9;
332 public static boolean imperial_units = false;
334 public static AltosDistance distance = new AltosDistance();
336 public static AltosHeight height = new AltosHeight();
338 public static AltosSpeed speed = new AltosSpeed();
340 public static AltosAccel accel = new AltosAccel();
342 public static AltosTemperature temperature = new AltosTemperature();
344 public static AltosOrient orient = new AltosOrient();
346 public static String show_gs(String format, double a) {
348 format = format.concat(" g");
349 return String.format(format, a);
352 public static String say_gs(double a) {
353 return String.format("%6.0 gees", meters_to_g(a));
356 public static int checksum(int[] data, int start, int length) {
358 for (int i = 0; i < length; i++)
359 csum += data[i + start];
363 public static double beep_value_to_freq(int value) {
366 return 1.0/2.0 * (24.0e6/32.0) / (double) value;
369 public static int beep_freq_to_value(double freq) {
372 return (int) Math.floor (1.0/2.0 * (24.0e6/32.0) / freq + 0.5);
375 public static final int BEARING_LONG = 0;
376 public static final int BEARING_SHORT = 1;
377 public static final int BEARING_VOICE = 2;
379 public static String bearing_to_words(int length, double bearing) {
380 String [][] bearing_string = {
382 "North", "North North East", "North East", "East North East",
383 "East", "East South East", "South East", "South South East",
384 "South", "South South West", "South West", "West South West",
385 "West", "West North West", "North West", "North North West"
387 "N", "NNE", "NE", "ENE",
388 "E", "ESE", "SE", "SSE",
389 "S", "SSW", "SW", "WSW",
390 "W", "WNW", "NW", "NNW"
392 "north", "nor nor east", "north east", "east nor east",
393 "east", "east sow east", "south east", "sow sow east",
394 "south", "sow sow west", "south west", "west sow west",
395 "west", "west nor west", "north west", "nor nor west "
398 return bearing_string[length][(int)((bearing / 90 * 8 + 1) / 2)%16];