/** ****************************************************************************** * @addtogroup OpenPilotModules OpenPilot Modules * @{ * @addtogroup AirspeedModule Airspeed Module * @brief Communicate with airspeed sensors and return values * @{ * * @file baro_airspeed_ms4525do.c * @author The OpenPilot Team, http://www.openpilot.org Copyright (C) 2014. * @brief Airspeed module, handles temperature and pressure readings from MS4525DO * * @see The GNU Public License (GPL) Version 3 * *****************************************************************************/ /* * 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, write to the Free Software Foundation, Inc., * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ /** * Output object: BaroAirspeed * * This module will periodically update the value of the BaroAirspeed object. * */ #include "openpilot.h" #include "hwsettings.h" #include "airspeedsettings.h" #include "airspeedsensor.h" // object that will be updated by the module #include "taskinfo.h" #if defined(PIOS_INCLUDE_MS4525DO) #define CALIBRATION_IDLE_MS 0 // Time to wait before calibrating, in [ms] #define CALIBRATION_COUNT_MS 4000 // Time to spend calibrating, in [ms] #define FILTER_SHIFT 5 // Barry Dorr filter parameter k #define P0 101325.0f // standard pressure #define CCEXPONENT 0.2857142857f // exponent of compressibility correction 2/7 #define CASFACTOR 760.8802669f // sqrt(5) * speed of sound at standard #define TASFACTOR 0.05891022589f // 1/sqrt(T0) #define max(x, y) ((x) >= (y) ? (x) : (y)) // Private types // Private functions definitions static int8_t baro_airspeedReadMS4525DO(AirspeedSensorData *airspeedSensor, AirspeedSettingsData *airspeedSettings); // Private variables static uint16_t calibrationCount = 0; static uint32_t filter_reg = 0; // Barry Dorr filter register void baro_airspeedGetMS4525DO(AirspeedSensorData *airspeedSensor, AirspeedSettingsData *airspeedSettings) { // request measurement first int8_t retVal = PIOS_MS4525DO_Request(); if (retVal != 0) { AlarmsSet(SYSTEMALARMS_ALARM_AIRSPEED, SYSTEMALARMS_ALARM_ERROR); return; } // Datasheet of MS4525DO: conversion needs 0.5 ms + 20% more when status bit used // delay by one Tick or at least 2 ms const portTickType xDelay = max(2 / portTICK_RATE_MS, 1); vTaskDelay(xDelay); // read the sensor retVal = baro_airspeedReadMS4525DO(airspeedSensor, airspeedSettings); switch (retVal) { case 0: AlarmsClear(SYSTEMALARMS_ALARM_AIRSPEED); break; case -4: case -5: case -7: AlarmsSet(SYSTEMALARMS_ALARM_AIRSPEED, SYSTEMALARMS_ALARM_WARNING); break; case -1: case -2: case -3: case -6: default: AlarmsSet(SYSTEMALARMS_ALARM_AIRSPEED, SYSTEMALARMS_ALARM_ERROR); } } // Private functions static int8_t baro_airspeedReadMS4525DO(AirspeedSensorData *airspeedSensor, AirspeedSettingsData *airspeedSettings) { // Check to see if airspeed sensor is returning airspeedSensor uint16_t values[2]; int8_t retVal = PIOS_MS4525DO_Read(values); if (retVal == 0) { airspeedSensor->SensorValue = values[0]; airspeedSensor->SensorValueTemperature = values[1]; } else { airspeedSensor->SensorValue = -1; airspeedSensor->SensorValueTemperature = -1; airspeedSensor->SensorConnected = AIRSPEEDSENSOR_SENSORCONNECTED_FALSE; airspeedSensor->CalibratedAirspeed = 0; return retVal; } // only calibrate if no stored calibration is available if (!airspeedSettings->ZeroPoint) { // Calibrate sensor by averaging zero point value if (calibrationCount <= CALIBRATION_IDLE_MS / airspeedSettings->SamplePeriod) { calibrationCount++; filter_reg = (airspeedSensor->SensorValue << FILTER_SHIFT); return -7; } else if (calibrationCount <= (CALIBRATION_IDLE_MS + CALIBRATION_COUNT_MS) / airspeedSettings->SamplePeriod) { calibrationCount++; // update filter register filter_reg = filter_reg - (filter_reg >> FILTER_SHIFT) + airspeedSensor->SensorValue; if (calibrationCount > (CALIBRATION_IDLE_MS + CALIBRATION_COUNT_MS) / airspeedSettings->SamplePeriod) { // Scale output for unity gain. airspeedSettings->ZeroPoint = (uint16_t)(filter_reg >> FILTER_SHIFT); AirspeedSettingsZeroPointSet(&airspeedSettings->ZeroPoint); calibrationCount = 0; } return -7; } } /* Compute airspeed assume sensor is A Type and has a range of 1 psi, i.e. Pmin=-1.0 psi and Pmax=1.0 psi Datasheet pressure: output = 0.8 * 16383 / (Pmax-Pmin) * (P - Pmin) + 0.1 * 16383 Inversion: P = (10*output - 81915)/65532 in psi 1 psi = 6894,757293168 Pa P = (10*output - 81915)*0.1052120688 in Pa Datasheet temperature: output = (T+50)*2047 / 200 Inversion: T = (200*out - 102350)/2047 in C T = (200*out - 102350)/2047 + 273.15 in K */ const float dP = (10 * (int32_t)(airspeedSensor->SensorValue - airspeedSettings->ZeroPoint)) * 0.1052120688f; const float T = (float)(200 * (int32_t)airspeedSensor->SensorValueTemperature - 102350) / 2047 + 273.15f; airspeedSensor->DifferentialPressure = dP; airspeedSensor->Temperature = T; // CAS = Csound * sqrt( 5 *( (dP/P0 +1)^(2/7) - 1) ) // TAS = Csound * sqrt( 5 T/T0 *( (dP/P0 +1)^(2/7) - 1) ) // where Csound = 340.276 m/s at standard condition T0=288.15 K and P0 = 101315 Pa airspeedSensor->CalibratedAirspeed = airspeedSettings->Scale * CASFACTOR * sqrtf(powf(fabsf(dP) / P0 + 1.0f, CCEXPONENT) - 1.0f); airspeedSensor->TrueAirspeed = airspeedSensor->CalibratedAirspeed * TASFACTOR * sqrtf(T); airspeedSensor->SensorConnected = AIRSPEEDSENSOR_SENSORCONNECTED_TRUE; return retVal; } #endif /* if defined(PIOS_INCLUDE_MS4525DO) */ /** * @} * @} */