src/main/drivers/pitotmeter/pitotmeter_adc.c

   1 /*
   2  * This file is part of Cleanflight.
   3  *
   4  * Cleanflight 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, either version 3 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * Cleanflight is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with Cleanflight.  If not, see <http://www.gnu.org/licenses/>.
  16  */
  17
  18 #include <stdbool.h>
  19 #include <stdint.h>
  20
  21 #include <platform.h>
  22
  23 #include "build/build_config.h"
  24
  25 #include "common/maths.h"
  26 #include "common/utils.h"
  27
  28 #include "drivers/pitotmeter/pitotmeter.h"
  29 #include "drivers/pitotmeter/pitotmeter_adc.h"
  30 #include "drivers/adc.h"
  31
  32 #if defined(USE_ADC) && defined(USE_PITOT_ADC)
  33
  34 /*
  35  * NXP MPXV7002DP differential pressure sensor
  36  *
  37  */
  38
  39 #define PITOT_ADC_VOLTAGE_SCALER        (2.0f / 1.0f)       // MPXV7002DP is 5V device, assumed resistive divider 1K:1K
  40 #define PITOT_ADC_VOLTAGE_ZERO          (2.5f)              // Pressure offset is 2.5V
  41 #define PITOT_ADC_VOLTAGE_TO_PRESSURE   (1000.0f)           // 1V/kPa = 1000 Pa/V
  42
  43 static bool adcPitotStart(pitotDev_t *pitot)
  44 {
  45     UNUSED(pitot);
  46     return true;
  47 }
  48
  49 static bool adcPitotRead(pitotDev_t *pitot)
  50 {
  51     UNUSED(pitot);
  52     return true;
  53 }
  54
  55 static void adcPitotCalculate(pitotDev_t *pitot, float *pressure, float *temperature)
  56 {
  57     UNUSED(pitot);
  58     uint16_t adcRaw = adcGetChannel(ADC_AIRSPEED);
  59     float voltage = (float)adcRaw * (3.3f / 4095.0f);  // 12 bit ADC with 3.3V VREF
  60
  61     if (pressure)
  62         *pressure = (voltage * PITOT_ADC_VOLTAGE_SCALER - PITOT_ADC_VOLTAGE_ZERO) * PITOT_ADC_VOLTAGE_TO_PRESSURE;
  63     if (temperature)
  64         *temperature = SSL_AIR_TEMPERATURE; // Temperature at standard sea level
  65 }
  66
  67 bool adcPitotDetect(pitotDev_t *pitot)
  68 {
  69     pitot->delay = 10000;
  70     pitot->calibThreshold = 0.00001f;   // TODO :: should be tested !!!
  71     pitot->start = adcPitotStart;
  72     pitot->get = adcPitotRead;
  73     pitot->calculate = adcPitotCalculate;
  74     return adcIsFunctionAssigned(ADC_AIRSPEED);
  75 }
  76 #endif