+++ /dev/null
-/*
- * Copyright © 2010 Keith Packard <keithp@keithp.com>
- *
- * 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.
- */
-
-/*
- * Sensor data conversion functions
- */
-package altosui;
-
-public class AltosConvert {
- /*
- * Pressure Sensor Model, version 1.1
- *
- * written by Holly Grimes
- *
- * Uses the International Standard Atmosphere as described in
- * "A Quick Derivation relating altitude to air pressure" (version 1.03)
- * from the Portland State Aerospace Society, except that the atmosphere
- * is divided into layers with each layer having a different lapse rate.
- *
- * Lapse rate data for each layer was obtained from Wikipedia on Sept. 1, 2007
- * at site <http://en.wikipedia.org/wiki/International_Standard_Atmosphere
- *
- * Height measurements use the local tangent plane. The postive z-direction is up.
- *
- * All measurements are given in SI units (Kelvin, Pascal, meter, meters/second^2).
- * The lapse rate is given in Kelvin/meter, the gas constant for air is given
- * in Joules/(kilogram-Kelvin).
- */
-
- static final double GRAVITATIONAL_ACCELERATION = -9.80665;
- static final double AIR_GAS_CONSTANT = 287.053;
- static final double NUMBER_OF_LAYERS = 7;
- static final double MAXIMUM_ALTITUDE = 84852.0;
- static final double MINIMUM_PRESSURE = 0.3734;
- static final double LAYER0_BASE_TEMPERATURE = 288.15;
- static final double LAYER0_BASE_PRESSURE = 101325;
-
- /* lapse rate and base altitude for each layer in the atmosphere */
- static final double[] lapse_rate = {
- -0.0065, 0.0, 0.001, 0.0028, 0.0, -0.0028, -0.002
- };
-
- static final int[] base_altitude = {
- 0, 11000, 20000, 32000, 47000, 51000, 71000
- };
-
- /* outputs atmospheric pressure associated with the given altitude.
- * altitudes are measured with respect to the mean sea level
- */
- static double
- altitude_to_pressure(double altitude)
- {
- double base_temperature = LAYER0_BASE_TEMPERATURE;
- double base_pressure = LAYER0_BASE_PRESSURE;
-
- double pressure;
- double base; /* base for function to determine pressure */
- double exponent; /* exponent for function to determine pressure */
- int layer_number; /* identifies layer in the atmosphere */
- double delta_z; /* difference between two altitudes */
-
- if (altitude > MAXIMUM_ALTITUDE) /* FIX ME: use sensor data to improve model */
- return 0;
-
- /* calculate the base temperature and pressure for the atmospheric layer
- associated with the inputted altitude */
- for(layer_number = 0; layer_number < NUMBER_OF_LAYERS - 1 && altitude > base_altitude[layer_number + 1]; layer_number++) {
- delta_z = base_altitude[layer_number + 1] - base_altitude[layer_number];
- if (lapse_rate[layer_number] == 0.0) {
- exponent = GRAVITATIONAL_ACCELERATION * delta_z
- / AIR_GAS_CONSTANT / base_temperature;
- base_pressure *= Math.exp(exponent);
- }
- else {
- base = (lapse_rate[layer_number] * delta_z / base_temperature) + 1.0;
- exponent = GRAVITATIONAL_ACCELERATION /
- (AIR_GAS_CONSTANT * lapse_rate[layer_number]);
- base_pressure *= Math.pow(base, exponent);
- }
- base_temperature += delta_z * lapse_rate[layer_number];
- }
-
- /* calculate the pressure at the inputted altitude */
- delta_z = altitude - base_altitude[layer_number];
- if (lapse_rate[layer_number] == 0.0) {
- exponent = GRAVITATIONAL_ACCELERATION * delta_z
- / AIR_GAS_CONSTANT / base_temperature;
- pressure = base_pressure * Math.exp(exponent);
- }
- else {
- base = (lapse_rate[layer_number] * delta_z / base_temperature) + 1.0;
- exponent = GRAVITATIONAL_ACCELERATION /
- (AIR_GAS_CONSTANT * lapse_rate[layer_number]);
- pressure = base_pressure * Math.pow(base, exponent);
- }
-
- return pressure;
- }
-
-
-/* outputs the altitude associated with the given pressure. the altitude
- returned is measured with respect to the mean sea level */
- static double
- pressure_to_altitude(double pressure)
- {
-
- double next_base_temperature = LAYER0_BASE_TEMPERATURE;
- double next_base_pressure = LAYER0_BASE_PRESSURE;
-
- double altitude;
- double base_pressure;
- double base_temperature;
- double base; /* base for function to determine base pressure of next layer */
- double exponent; /* exponent for function to determine base pressure
- of next layer */
- double coefficient;
- int layer_number; /* identifies layer in the atmosphere */
- int delta_z; /* difference between two altitudes */
-
- if (pressure < 0) /* illegal pressure */
- return -1;
- if (pressure < MINIMUM_PRESSURE) /* FIX ME: use sensor data to improve model */
- return MAXIMUM_ALTITUDE;
-
- /* calculate the base temperature and pressure for the atmospheric layer
- associated with the inputted pressure. */
- layer_number = -1;
- do {
- layer_number++;
- base_pressure = next_base_pressure;
- base_temperature = next_base_temperature;
- delta_z = base_altitude[layer_number + 1] - base_altitude[layer_number];
- if (lapse_rate[layer_number] == 0.0) {
- exponent = GRAVITATIONAL_ACCELERATION * delta_z
- / AIR_GAS_CONSTANT / base_temperature;
- next_base_pressure *= Math.exp(exponent);
- }
- else {
- base = (lapse_rate[layer_number] * delta_z / base_temperature) + 1.0;
- exponent = GRAVITATIONAL_ACCELERATION /
- (AIR_GAS_CONSTANT * lapse_rate[layer_number]);
- next_base_pressure *= Math.pow(base, exponent);
- }
- next_base_temperature += delta_z * lapse_rate[layer_number];
- }
- while(layer_number < NUMBER_OF_LAYERS - 1 && pressure < next_base_pressure);
-
- /* calculate the altitude associated with the inputted pressure */
- if (lapse_rate[layer_number] == 0.0) {
- coefficient = (AIR_GAS_CONSTANT / GRAVITATIONAL_ACCELERATION)
- * base_temperature;
- altitude = base_altitude[layer_number]
- + coefficient * Math.log(pressure / base_pressure);
- }
- else {
- base = pressure / base_pressure;
- exponent = AIR_GAS_CONSTANT * lapse_rate[layer_number]
- / GRAVITATIONAL_ACCELERATION;
- coefficient = base_temperature / lapse_rate[layer_number];
- altitude = base_altitude[layer_number]
- + coefficient * (Math.pow(base, exponent) - 1);
- }
-
- return altitude;
- }
-
- static double
- cc_battery_to_voltage(double battery)
- {
- return battery / 32767.0 * 5.0;
- }
-
- static double
- cc_ignitor_to_voltage(double ignite)
- {
- return ignite / 32767 * 15.0;
- }
-
- static double radio_to_frequency(int freq, int setting, int cal, int channel) {
- double f;
-
- if (freq > 0)
- f = freq / 1000.0;
- else {
- if (setting <= 0)
- setting = cal;
- f = 434.550 * setting / cal;
- /* Round to nearest 50KHz */
- f = Math.floor (20.0 * f + 0.5) / 20.0;
- }
- return f + channel * 0.100;
- }
-
- static int radio_frequency_to_setting(double frequency, int cal) {
- double set = frequency / 434.550 * cal;
-
- return (int) Math.floor (set + 0.5);
- }
-
- static int radio_frequency_to_channel(double frequency) {
- int channel = (int) Math.floor ((frequency - 434.550) / 0.100 + 0.5);
-
- if (channel < 0)
- channel = 0;
- if (channel > 9)
- channel = 9;
- return channel;
- }
-
- static double radio_channel_to_frequency(int channel) {
- return 434.550 + channel * 0.100;
- }
-
- static int[] ParseHex(String line) {
- String[] tokens = line.split("\\s+");
- int[] array = new int[tokens.length];
-
- for (int i = 0; i < tokens.length; i++)
- try {
- array[i] = Integer.parseInt(tokens[i], 16);
- } catch (NumberFormatException ne) {
- return null;
- }
- return array;
- }
-
- static double meters_to_feet(double meters) {
- return meters * (100 / (2.54 * 12));
- }
-
- static double meters_to_mach(double meters) {
- return meters / 343; /* something close to mach at usual rocket sites */
- }
-
- static double meters_to_g(double meters) {
- return meters / 9.80665;
- }
-
- static int checksum(int[] data, int start, int length) {
- int csum = 0x5a;
- for (int i = 0; i < length; i++)
- csum += data[i + start];
- return csum & 0xff;
- }
-}
projects / fw / altos / blobdiff