ardupilot/Arducopter/Sensors.pde

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/*
ArduCopter v1.3 - August 2010
www.ArduCopter.com
Copyright (c) 2010. All rights reserved.
An Open Source Arduino based multicopter.
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, either version 3 of the License, or
(at your option) any later version.
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, see <http://www.gnu.org/licenses/>.
*/
void ReadSCP1000(void) {
}
#ifdef UseBMP
void read_airpressure(void){
double x;
APM_BMP085.Read(); //Get new data from absolute pressure sensor
abs_press = APM_BMP085.Press;
abs_press_filt = (abs_press); // + 2l * abs_press_filt) / 3l; //Light filtering
//temperature = (temperature * 9 + temp_unfilt) / 10; We will just use the ground temp for the altitude calculation
double p = (double)abs_press_gnd / (double)abs_press_filt;
double temp = (float)ground_temperature / 10.f + 273.15f;
x = log(p) * temp * 29271.267f;
//x = log(p) * temp * 29.271267 * 1000;
press_alt = (int)(x / 10) + ground_alt; // Pressure altitude in centimeters
// Need to add comments for theory.....
}
#endif
#ifdef UseAirspeed
void read_airspeed(void) {
#if GCS_PROTOCOL != 3 // Xplane will supply the airspeed
airpressure_raw = ((float)analogRead(AIRSPEED_PIN) * .25) + (airpressure_raw * .75);
airpressure = (int)airpressure_raw - airpressure_offset;
airspeed = sqrt((float)airpressure / AIRSPEED_RATIO);
#endif
airspeed_error = airspeed_cruise - airspeed;
}
#endif
#if BATTERY_EVENT == 1
void read_battery(void)
{
battery_voltage = BATTERY_VOLTAGE(analogRead(BATTERY_PIN)) * .1 + battery_voltage * .9;
if(battery_voltage < LOW_VOLTAGE)
low_battery_event();
}
#endif
#ifdef UseAirspeed
void zero_airspeed(void)
{
airpressure_raw = analogRead(AIRSPEED_PIN);
for(int c=0; c < 80; c++){
airpressure_raw = (airpressure_raw * .90) + ((float)analogRead(AIRSPEED_PIN) * .10);
}
airpressure_offset = airpressure_raw;
}
#endif