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   1 /*
   2  * Copyright © 2010 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 /*
  19  * Sensor data conversion functions
  20  */
  21 package org.altusmetrum.altoslib_4;
  22
  23 public class AltosConvert {
  24         /*
  25          * Pressure Sensor Model, version 1.1
  26          *
  27          * written by Holly Grimes
  28          *
  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.
  33          *
  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
  36          *
  37          * Height measurements use the local tangent plane.  The postive z-direction is up.
  38          *
  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).
  42          */
  43
  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;
  51
  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
  55         };
  56
  57         public static final int[] base_altitude = {
  58                 0, 11000, 20000, 32000, 47000, 51000, 71000
  59         };
  60
  61         /* outputs atmospheric pressure associated with the given altitude.
  62          * altitudes are measured with respect to the mean sea level
  63          */
  64         public static double
  65         altitude_to_pressure(double altitude)
  66         {
  67                 double base_temperature = LAYER0_BASE_TEMPERATURE;
  68                 double base_pressure = LAYER0_BASE_PRESSURE;
  69
  70                 double 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 */
  75
  76                 if (altitude > MAXIMUM_ALTITUDE) /* FIX ME: use sensor data to improve model */
  77                         return 0;
  78
  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);
  87                         }
  88                         else {
  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);
  93                         }
  94                         base_temperature += delta_z * lapse_rate[layer_number];
  95                 }
  96
  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);
 103                 }
 104                 else {
 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);
 109                 }
 110
 111                 return pressure;
 112         }
 113
 114
 115 /* outputs the altitude associated with the given pressure. the altitude
 116    returned is measured with respect to the mean sea level */
 117         public static double
 118         pressure_to_altitude(double pressure)
 119         {
 120
 121                 double next_base_temperature = LAYER0_BASE_TEMPERATURE;
 122                 double next_base_pressure = LAYER0_BASE_PRESSURE;
 123
 124                 double altitude;
 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
 129                                     of next layer */
 130                 double coefficient;
 131                 int layer_number; /* identifies layer in the atmosphere */
 132                 int delta_z; /* difference between two altitudes */
 133
 134                 if (pressure < 0)  /* illegal pressure */
 135                         return -1;
 136                 if (pressure < MINIMUM_PRESSURE) /* FIX ME: use sensor data to improve model */
 137                         return MAXIMUM_ALTITUDE;
 138
 139                 /* calculate the base temperature and pressure for the atmospheric layer
 140                    associated with the inputted pressure. */
 141                 layer_number = -1;
 142                 do {
 143                         layer_number++;
 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);
 151                         }
 152                         else {
 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);
 157                         }
 158                         next_base_temperature += delta_z * lapse_rate[layer_number];
 159                 }
 160                 while(layer_number < NUMBER_OF_LAYERS - 1 && pressure < next_base_pressure);
 161
 162                 /* calculate the altitude associated with the inputted pressure */
 163                 if (lapse_rate[layer_number] == 0.0) {
 164                         coefficient = (AIR_GAS_CONSTANT / GRAVITATIONAL_ACCELERATION)
 165                                 * base_temperature;
 166                         altitude = base_altitude[layer_number]
 167                                 + coefficient * Math.log(pressure / base_pressure);
 168                 }
 169                 else {
 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);
 176                 }
 177
 178                 return altitude;
 179         }
 180
 181         public static double
 182         cc_battery_to_voltage(double battery)
 183         {
 184                 return battery / 32767.0 * 5.0;
 185         }
 186
 187         public static double
 188         cc_ignitor_to_voltage(double ignite)
 189         {
 190                 return ignite / 32767 * 15.0;
 191         }
 192
 193         public static double
 194         barometer_to_pressure(double count)
 195         {
 196                 return ((count / 16.0) / 2047.0 + 0.095) / 0.009 * 1000.0;
 197         }
 198
 199         static double
 200         thermometer_to_temperature(double thermo)
 201         {
 202                 return (thermo - 19791.268) / 32728.0 * 1.25 / 0.00247;
 203         }
 204
 205         static double mega_adc(int raw) {
 206                 return raw / 4095.0;
 207         }
 208
 209         static public double mega_battery_voltage(int v_batt) {
 210                 if (v_batt != AltosLib.MISSING)
 211                         return 3.3 * mega_adc(v_batt) * (5.6 + 10.0) / 10.0;
 212                 return AltosLib.MISSING;
 213         }
 214
 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;
 219         }
 220
 221         static double tele_mini_voltage(int sensor) {
 222                 double  supply = 3.3;
 223
 224                 return sensor / 32767.0 * supply * 127/27;
 225         }
 226
 227         static double easy_mini_voltage(int sensor, int serial) {
 228                 double  supply = 3.3;
 229                 double  diode_offset = 0.0;
 230
 231                 /* early prototypes had a 3.0V regulator */
 232                 if (serial < 1000)
 233                         supply = 3.0;
 234
 235                 /* Purple v1.0 boards had the sensor after the
 236                  * blocking diode, which drops about 150mV
 237                  */
 238                 if (serial < 1665)
 239                         diode_offset = 0.150;
 240
 241                 return sensor / 32767.0 * supply * 127/27 + diode_offset;
 242         }
 243
 244         public static double radio_to_frequency(int freq, int setting, int cal, int channel) {
 245                 double  f;
 246
 247                 if (freq > 0)
 248                         f = freq / 1000.0;
 249                 else {
 250                         if (setting <= 0)
 251                                 setting = cal;
 252                         f = 434.550 * setting / cal;
 253                         /* Round to nearest 50KHz */
 254                         f = Math.floor (20.0 * f + 0.5) / 20.0;
 255                 }
 256                 return f + channel * 0.100;
 257         }
 258
 259         public static int radio_frequency_to_setting(double frequency, int cal) {
 260                 double  set = frequency / 434.550 * cal;
 261
 262                 return (int) Math.floor (set + 0.5);
 263         }
 264
 265         public static int radio_frequency_to_channel(double frequency) {
 266                 int     channel = (int) Math.floor ((frequency - 434.550) / 0.100 + 0.5);
 267
 268                 if (channel < 0)
 269                         channel = 0;
 270                 if (channel > 9)
 271                         channel = 9;
 272                 return channel;
 273         }
 274
 275         public static double radio_channel_to_frequency(int channel) {
 276                 return 434.550 + channel * 0.100;
 277         }
 278
 279         public static int[] ParseHex(String line) {
 280                 String[] tokens = line.split("\\s+");
 281                 int[] array = new int[tokens.length];
 282
 283                 for (int i = 0; i < tokens.length; i++)
 284                         try {
 285                                 array[i] = Integer.parseInt(tokens[i], 16);
 286                         } catch (NumberFormatException ne) {
 287                                 return null;
 288                         }
 289                 return array;
 290         }
 291
 292         public static double meters_to_feet(double meters) {
 293                 return meters * (100 / (2.54 * 12));
 294         }
 295
 296         public static double feet_to_meters(double feet) {
 297                 return feet * 12 * 2.54 / 100.0;
 298         }
 299
 300         public static double meters_to_miles(double meters) {
 301                 return meters_to_feet(meters) / 5280;
 302         }
 303
 304         public static double miles_to_meters(double miles) {
 305                 return feet_to_meters(miles * 5280);
 306         }
 307
 308         public static double meters_to_mph(double mps) {
 309                 return meters_to_miles(mps) * 3600;
 310         }
 311
 312         public static double mph_to_meters(double mps) {
 313                 return miles_to_meters(mps) / 3600;
 314         }
 315
 316         public static double meters_to_mach(double meters) {
 317                 return meters / 343;            /* something close to mach at usual rocket sites */
 318         }
 319
 320         public static double meters_to_g(double meters) {
 321                 return meters / 9.80665;
 322         }
 323
 324         public static double c_to_f(double c) {
 325                 return c * 9/5 + 32;
 326         }
 327
 328         public static double f_to_c(double c) {
 329                 return (c - 32) * 5/9;
 330         }
 331
 332         public static boolean imperial_units = false;
 333
 334         public static AltosDistance distance = new AltosDistance();
 335
 336         public static AltosHeight height = new AltosHeight();
 337
 338         public static AltosSpeed speed = new AltosSpeed();
 339
 340         public static AltosAccel accel = new AltosAccel();
 341
 342         public static AltosTemperature temperature = new AltosTemperature();
 343
 344         public static AltosOrient orient = new AltosOrient();
 345
 346         public static String show_gs(String format, double a) {
 347                 a = meters_to_g(a);
 348                 format = format.concat(" g");
 349                 return String.format(format, a);
 350         }
 351
 352         public static String say_gs(double a) {
 353                 return String.format("%6.0 gees", meters_to_g(a));
 354         }
 355
 356         public static int checksum(int[] data, int start, int length) {
 357                 int     csum = 0x5a;
 358                 for (int i = 0; i < length; i++)
 359                         csum += data[i + start];
 360                 return csum & 0xff;
 361         }
 362
 363         public static double beep_value_to_freq(int value) {
 364                 if (value == 0)
 365                         return 4000;
 366                 return 1.0/2.0 * (24.0e6/32.0) / (double) value;
 367         }
 368
 369         public static int beep_freq_to_value(double freq) {
 370                 if (freq == 0)
 371                         return 94;
 372                 return (int) Math.floor (1.0/2.0 * (24.0e6/32.0) / freq + 0.5);
 373         }
 374
 375         public static final int BEARING_LONG = 0;
 376         public static final int BEARING_SHORT = 1;
 377         public static final int BEARING_VOICE = 2;
 378
 379         public static String bearing_to_words(int length, double bearing) {
 380                 String [][] bearing_string = {
 381                         {
 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"
 386                         }, {
 387                                 "N", "NNE", "NE", "ENE",
 388                                 "E", "ESE", "SE", "SSE",
 389                                 "S", "SSW", "SW", "WSW",
 390                                 "W", "WNW", "NW", "NNW"
 391                         }, {
 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 "
 396                         }
 397                 };
 398                 return bearing_string[length][(int)((bearing / 90 * 8 + 1) / 2)%16];
 399         }
 400 }