AP_Airspeed: added ARSP_PSI_RANGE parameter

for using pressure sensors with a different range

libraries/AP_Airspeed/AP_Airspeed.cpp

@@ -64,10 +64,17 @@ extern const AP_HAL::HAL &hal;
     #else
          #define ARSPD_DEFAULT_PIN AP_AIRSPEED_I2C_PIN
     #endif
+    #if CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_DISCO
+         #define PSI_RANGE_DEFAULT 0.05
+    #endif
 #else
  #define ARSPD_DEFAULT_PIN 0
 #endif
 
+#ifndef PSI_RANGE_DEFAULT
+#define PSI_RANGE_DEFAULT 1.0f
+#endif
+
 // table of user settable parameters
 const AP_Param::GroupInfo AP_Airspeed::var_info[] = {
 
@@ -120,6 +127,12 @@ const AP_Param::GroupInfo AP_Airspeed::var_info[] = {
     // @User: Advanced
     AP_GROUPINFO("SKIP_CAL",  7, AP_Airspeed, _skip_cal, 0),
 
+    // @Param: PSI_RANGE
+    // @DisplayName: The PSI range of the device
+    // @Description: This parameter allows you to to set the PSI (pounds per square inch) range for your sensor. You should not change this unless you examine the datasheet for your device
+    // @User: Advanced
+    AP_GROUPINFO("PSI_RANGE",  8, AP_Airspeed, _psi_range, PSI_RANGE_DEFAULT),
+    
     AP_GROUPEND
 };
 
@@ -127,7 +140,6 @@ const AP_Param::GroupInfo AP_Airspeed::var_info[] = {
 AP_Airspeed::AP_Airspeed(const AP_Vehicle::FixedWing &parms)
     : _EAS2TAS(1.0f)
     , _calibration(parms)
-    , analog(_pin)
 {
     AP_Param::setup_object_defaults(this, var_info);
 }

libraries/AP_Airspeed/AP_Airspeed.h

@@ -149,6 +149,7 @@ public:
 private:
     AP_Float        _offset;
     AP_Float        _ratio;
+    AP_Float        _psi_range;
     AP_Int8         _use;
     AP_Int8         _enable;
     AP_Int8         _pin;
@@ -180,10 +181,10 @@ private:
     float get_pressure(void);
     void update_calibration(float raw_pressure);
 
-    AP_Airspeed_Analog analog;
+    AP_Airspeed_Analog analog{_pin, _psi_range};
 #if CONFIG_HAL_BOARD == HAL_BOARD_PX4 || CONFIG_HAL_BOARD == HAL_BOARD_VRBRAIN
-    AP_Airspeed_PX4    digital;
+    AP_Airspeed_PX4    digital{_psi_range};
 #else
-    AP_Airspeed_I2C    digital;
+    AP_Airspeed_I2C    digital{_psi_range};
 #endif
 };

libraries/AP_Airspeed/AP_Airspeed_I2C.cpp

@@ -37,6 +37,11 @@ extern const AP_HAL::HAL &hal;
 #define MS4525D0_I2C_BUS 1
 #endif
 
+AP_Airspeed_I2C::AP_Airspeed_I2C(const AP_Float &psi_range) :
+    _psi_range(psi_range)
+{
+}
+
 // probe and initialise the sensor
 bool AP_Airspeed_I2C::init()
 {
@@ -91,8 +96,8 @@ void AP_Airspeed_I2C::_collect()
     dT_raw = (data[2] << 8) + data[3];
     dT_raw = (0xFFE0 & dT_raw) >> 5;
 
-    const float P_min = -1.0f;
-    const float P_max = 1.0f;
+    const float P_max = _psi_range.get();
+    const float P_min = - P_max;
     const float PSI_to_Pa = 6894.757f;
     /*
       this equation is an inversion of the equation in the

libraries/AP_Airspeed/AP_Airspeed_I2C.h

@@ -21,6 +21,10 @@
  */
 
 #include <AP_HAL/AP_HAL.h>
+#include <AP_Param/AP_Param.h>
+#include <AP_HAL/utility/OwnPtr.h>
+#include <AP_HAL/I2CDevice.h>
+#include <utility>
 
 #include "AP_Airspeed_Backend.h"
 #include <AP_HAL/I2CDevice.h>
@@ -28,6 +32,9 @@
 class AP_Airspeed_I2C : public AP_Airspeed_Backend
 {
 public:
+    AP_Airspeed_I2C(const AP_Float &psi_range);
+    ~AP_Airspeed_I2C(void) {}
+    
     // probe and initialise the sensor
     bool init();
 
@@ -46,4 +53,5 @@ private:
     uint32_t _last_sample_time_ms;
     uint32_t _measurement_started_ms;
     AP_HAL::OwnPtr<AP_HAL::I2CDevice> _dev;
+    const AP_Float &_psi_range;
 };

libraries/AP_Airspeed/AP_Airspeed_PX4.cpp

@@ -61,7 +61,7 @@ bool AP_Airspeed_PX4::get_differential_pressure(float &pressure)
 
     while (::read(_fd, &report, sizeof(report)) == sizeof(report) &&
            report.timestamp != _last_timestamp) {
-        psum += report.differential_pressure_raw_pa;
+        psum += report.differential_pressure_raw_pa / _psi_range.get();
         tsum += report.temperature;
         count++;
         _last_timestamp = report.timestamp;

libraries/AP_Airspeed/AP_Airspeed_PX4.h

@@ -21,12 +21,14 @@
  */
 
 #include <AP_HAL/AP_HAL.h>
+#include <AP_Param/AP_Param.h>
 #include "AP_Airspeed_Backend.h"
 
 class AP_Airspeed_PX4 : public AP_Airspeed_Backend {
 public:
     // constructor
-    AP_Airspeed_PX4() : _fd(-1) {}
+    AP_Airspeed_PX4(const AP_Float &psi_range) :
+        _psi_range(psi_range) {}
 
     // probe and initialise the sensor
     bool init(void);
@@ -38,7 +40,8 @@ public:
     bool get_temperature(float &temperature);
 
 private:
-    int _fd;
+    int _fd = -1;
     uint64_t _last_timestamp;
     float _temperature;
+    const AP_Float &_psi_range;
 };

libraries/AP_Airspeed/AP_Airspeed_analog.cpp

@@ -42,6 +42,6 @@ bool AP_Airspeed_Analog::get_differential_pressure(float &pressure)
         return false;
     }
     _source->set_pin(_pin);
-    pressure = _source->voltage_average_ratiometric() * VOLTS_TO_PASCAL;
+    pressure = _source->voltage_average_ratiometric() * VOLTS_TO_PASCAL / _psi_range.get();
     return true;
 }

libraries/AP_Airspeed/AP_Airspeed_analog.h

@@ -9,9 +9,10 @@
 class AP_Airspeed_Analog : public AP_Airspeed_Backend
 {
 public:
-    AP_Airspeed_Analog(const AP_Int8 &pin)
+    AP_Airspeed_Analog(const AP_Int8 &pin, const AP_Float &psi_range)
         : _source(NULL)
         , _pin(pin)
+        , _psi_range(psi_range)
     { }
 
     // probe and initialise the sensor
@@ -26,4 +27,5 @@ public:
 private:
     AP_HAL::AnalogSource *_source;
     const AP_Int8 &_pin;
+    const AP_Float &_psi_range;
 };