From b450a96698431d2675bbe5c827e200fb551dfa39 Mon Sep 17 00:00:00 2001
From: Peter Barker <pbarker@barker.dropbear.id.au>
Date: Tue, 20 Jul 2021 23:04:20 +1000
Subject: [PATCH] AP_AHRS: shuffle AP_AHRS classes

---
 libraries/AP_AHRS/AP_AHRS.cpp                 |  54 ++---
 libraries/AP_AHRS/AP_AHRS.h                   |  37 +---
 libraries/AP_AHRS/AP_AHRS_DCM.h               |   6 +-
 libraries/AP_AHRS/AP_AHRS_Logging.cpp         |  10 +-
 libraries/AP_AHRS/AP_AHRS_NavEKF.cpp          | 189 ++++++++++--------
 libraries/AP_AHRS/AP_AHRS_NavEKF.h            |  34 +++-
 .../AP_AHRS/examples/AHRS_Test/AHRS_Test.cpp  |   4 +-
 7 files changed, 166 insertions(+), 168 deletions(-)

diff --git a/libraries/AP_AHRS/AP_AHRS.cpp b/libraries/AP_AHRS/AP_AHRS.cpp
index f9a6fae83f..b580243e81 100644
--- a/libraries/AP_AHRS/AP_AHRS.cpp
+++ b/libraries/AP_AHRS/AP_AHRS.cpp
@@ -165,7 +165,7 @@ const AP_Param::GroupInfo AP_AHRS::var_info[] = {
 };
 
 // init sets up INS board orientation
-void AP_AHRS::init()
+void AP_AHRS_Backend::init()
 {
     update_orientation();
 
@@ -175,14 +175,14 @@ void AP_AHRS::init()
 }
 
 // return a smoothed and corrected gyro vector using the latest ins data (which may not have been consumed by the EKF yet)
-Vector3f AP_AHRS::get_gyro_latest(void) const
+Vector3f AP_AHRS_Backend::get_gyro_latest(void) const
 {
     const uint8_t primary_gyro = get_primary_gyro_index();
     return AP::ins().get_gyro(primary_gyro) + get_gyro_drift();
 }
 
 // set_trim
-void AP_AHRS::set_trim(const Vector3f &new_trim)
+void AP_AHRS_Backend::set_trim(const Vector3f &new_trim)
 {
     Vector3f trim;
     trim.x = constrain_float(new_trim.x, ToRad(-AP_AHRS_TRIM_LIMIT), ToRad(AP_AHRS_TRIM_LIMIT));
@@ -191,7 +191,7 @@ void AP_AHRS::set_trim(const Vector3f &new_trim)
 }
 
 // add_trim - adjust the roll and pitch trim up to a total of 10 degrees
-void AP_AHRS::add_trim(float roll_in_radians, float pitch_in_radians, bool save_to_eeprom)
+void AP_AHRS_Backend::add_trim(float roll_in_radians, float pitch_in_radians, bool save_to_eeprom)
 {
     Vector3f trim = _trim.get();
 
@@ -209,7 +209,7 @@ void AP_AHRS::add_trim(float roll_in_radians, float pitch_in_radians, bool save_
 }
 
 // Set the board mounting orientation, may be called while disarmed
-void AP_AHRS::update_orientation()
+void AP_AHRS_Backend::update_orientation()
 {
     const enum Rotation orientation = (enum Rotation)_board_orientation.get();
     if (orientation != ROTATION_CUSTOM) {
@@ -227,7 +227,7 @@ void AP_AHRS::update_orientation()
 }
 
 // return a ground speed estimate in m/s
-Vector2f AP_AHRS::groundspeed_vector(void)
+Vector2f AP_AHRS_Backend::groundspeed_vector(void)
 {
     // Generate estimate of ground speed vector using air data system
     Vector2f gndVelADS;
@@ -296,7 +296,7 @@ Vector2f AP_AHRS::groundspeed_vector(void)
 /*
   calculate sin and cos of roll/pitch/yaw from a body_to_ned rotation matrix
  */
-void AP_AHRS::calc_trig(const Matrix3f &rot,
+void AP_AHRS_Backend::calc_trig(const Matrix3f &rot,
                         float &cr, float &cp, float &cy,
                         float &sr, float &sp, float &sy) const
 {
@@ -342,7 +342,7 @@ void AP_AHRS::calc_trig(const Matrix3f &rot,
 
 // update_trig - recalculates _cos_roll, _cos_pitch, etc based on latest attitude
 //      should be called after _dcm_matrix is updated
-void AP_AHRS::update_trig(void)
+void AP_AHRS_Backend::update_trig(void)
 {
     if (_last_trim != _trim.get()) {
         _last_trim = _trim.get();
@@ -358,7 +358,7 @@ void AP_AHRS::update_trig(void)
 /*
   update the centi-degree values
  */
-void AP_AHRS::update_cd_values(void)
+void AP_AHRS_Backend::update_cd_values(void)
 {
     roll_sensor  = degrees(roll) * 100;
     pitch_sensor = degrees(pitch) * 100;
@@ -393,7 +393,7 @@ AP_AHRS_View *AP_AHRS::create_view(enum Rotation rotation, float pitch_trim_deg)
  * "ANGLE OF ATTACK AND SIDESLIP ESTIMATION USING AN INERTIAL REFERENCE PLATFORM" by
  * JOSEPH E. ZEIS, JR., CAPTAIN, USAF
  */
-void AP_AHRS::update_AOA_SSA(void)
+void AP_AHRS_Backend::update_AOA_SSA(void)
 {
 #if APM_BUILD_TYPE(APM_BUILD_ArduPlane)
     const uint32_t now = AP_HAL::millis();
@@ -440,35 +440,35 @@ void AP_AHRS::update_AOA_SSA(void)
 }
 
 // return current AOA
-float AP_AHRS::getAOA(void)
+float AP_AHRS_Backend::getAOA(void)
 {
     update_AOA_SSA();
     return _AOA;
 }
 
 // return calculated SSA
-float AP_AHRS::getSSA(void)
+float AP_AHRS_Backend::getSSA(void)
 {
     update_AOA_SSA();
     return _SSA;
 }
 
 // rotate a 2D vector from earth frame to body frame
-Vector2f AP_AHRS::earth_to_body2D(const Vector2f &ef) const
+Vector2f AP_AHRS_Backend::earth_to_body2D(const Vector2f &ef) const
 {
     return Vector2f(ef.x * _cos_yaw + ef.y * _sin_yaw,
                     -ef.x * _sin_yaw + ef.y * _cos_yaw);
 }
 
 // rotate a 2D vector from earth frame to body frame
-Vector2f AP_AHRS::body_to_earth2D(const Vector2f &bf) const
+Vector2f AP_AHRS_Backend::body_to_earth2D(const Vector2f &bf) const
 {
     return Vector2f(bf.x * _cos_yaw - bf.y * _sin_yaw,
                     bf.x * _sin_yaw + bf.y * _cos_yaw);
 }
 
 // log ahrs home and EKF origin
-void AP_AHRS::Log_Write_Home_And_Origin()
+void AP_AHRS_Backend::Log_Write_Home_And_Origin()
 {
     AP_Logger *logger = AP_Logger::get_singleton();
     if (logger == nullptr) {
@@ -485,11 +485,11 @@ void AP_AHRS::Log_Write_Home_And_Origin()
 }
 
 // get apparent to true airspeed ratio
-float AP_AHRS::get_EAS2TAS(void) const {
+float AP_AHRS_Backend::get_EAS2TAS(void) const {
     return AP::baro().get_EAS2TAS();
 }
 
-void AP_AHRS::update_nmea_out()
+void AP_AHRS_Backend::update_nmea_out()
 {
 #if !HAL_MINIMIZE_FEATURES
     if (_nmea_out != nullptr) {
@@ -499,18 +499,18 @@ void AP_AHRS::update_nmea_out()
 }
 
 // return current vibration vector for primary IMU
-Vector3f AP_AHRS::get_vibration(void) const
+Vector3f AP_AHRS_Backend::get_vibration(void) const
 {
     return AP::ins().get_vibration_levels();
 }
 
-void AP_AHRS::set_takeoff_expected(bool b)
+void AP_AHRS_Backend::set_takeoff_expected(bool b)
 {
     _flags.takeoff_expected = b;
     takeoff_expected_start_ms = AP_HAL::millis();
 }
 
-void AP_AHRS::set_touchdown_expected(bool b)
+void AP_AHRS_Backend::set_touchdown_expected(bool b)
 {
     _flags.touchdown_expected = b;
     touchdown_expected_start_ms = AP_HAL::millis();
@@ -519,7 +519,7 @@ void AP_AHRS::set_touchdown_expected(bool b)
 /*
   update takeoff/touchdown flags
  */
-void AP_AHRS::update_flags(void)
+void AP_AHRS_Backend::update_flags(void)
 {
     const uint32_t timeout_ms = 1000;
     if (_flags.takeoff_expected && AP_HAL::millis() - takeoff_expected_start_ms > timeout_ms) {
@@ -529,15 +529,3 @@ void AP_AHRS::update_flags(void)
         _flags.touchdown_expected = false;
     }
 }
-
-// singleton instance
-AP_AHRS *AP_AHRS::_singleton;
-
-namespace AP {
-
-AP_AHRS &ahrs()
-{
-    return *AP_AHRS::get_singleton();
-}
-
-}
diff --git a/libraries/AP_AHRS/AP_AHRS.h b/libraries/AP_AHRS/AP_AHRS.h
index ebea920427..8bcd6acdd3 100644
--- a/libraries/AP_AHRS/AP_AHRS.h
+++ b/libraries/AP_AHRS/AP_AHRS.h
@@ -43,26 +43,17 @@ enum AHRS_VehicleClass : uint8_t {
 };
 
 
-// forward declare view class
-class AP_AHRS_View;
-
-class AP_AHRS
+class AP_AHRS_Backend
 {
 public:
-    friend class AP_AHRS_View;
 
     // Constructor
-    AP_AHRS() :
+    AP_AHRS_Backend() :
         _vehicle_class(AHRS_VEHICLE_UNKNOWN),
         _cos_roll(1.0f),
         _cos_pitch(1.0f),
         _cos_yaw(1.0f)
     {
-        _singleton = this;
-
-        // load default values from var_info table
-        AP_Param::setup_object_defaults(this, var_info);
-
         // base the ki values by the sensors maximum drift
         // rate.
         _gyro_drift_limit = AP::ins().get_gyro_drift_rate();
@@ -76,12 +67,7 @@ public:
     }
 
     // empty virtual destructor
-    virtual ~AP_AHRS() {}
-
-    // get singleton instance
-    static AP_AHRS *get_singleton() {
-        return _singleton;
-    }
+    virtual ~AP_AHRS_Backend() {}
 
     // init sets up INS board orientation
     virtual void init();
@@ -543,9 +529,6 @@ public:
         AP::ins().get_delta_velocity(ret, dt);
     }
 
-    // create a view
-    AP_AHRS_View *create_view(enum Rotation rotation, float pitch_trim_deg=0);
-
     // return calculated AOA
     float getAOA(void);
 
@@ -601,9 +584,6 @@ public:
     // active AHRS type for logging
     virtual uint8_t get_active_AHRS_type(void) const { return 0; }
 
-    // for holding parameters
-    static const struct AP_Param::GroupInfo var_info[];
-
     // Logging to disk functions
     void Write_AHRS2(void) const;
     void Write_AOA_SSA(void);  // should be const? but it calls update functions
@@ -711,15 +691,11 @@ protected:
     // which accelerometer instance is active
     uint8_t _active_accel_instance;
 
-    // optional view class
-    AP_AHRS_View *_view;
-
     // AOA and SSA
     float _AOA, _SSA;
     uint32_t _last_AOA_update_ms;
 
 private:
-    static AP_AHRS *_singleton;
 
     AP_NMEA_Output* _nmea_out;
 
@@ -727,11 +703,4 @@ private:
     uint32_t touchdown_expected_start_ms;
 };
 
-#include "AP_AHRS_DCM.h"
 #include "AP_AHRS_NavEKF.h"
-
-namespace AP {
-    AP_AHRS &ahrs();
-    // ahrs_navekf only exists to avoid code churn
-    AP_AHRS_NavEKF &ahrs_navekf();
-};
diff --git a/libraries/AP_AHRS/AP_AHRS_DCM.h b/libraries/AP_AHRS/AP_AHRS_DCM.h
index 84ae8addb7..577043fec6 100644
--- a/libraries/AP_AHRS/AP_AHRS_DCM.h
+++ b/libraries/AP_AHRS/AP_AHRS_DCM.h
@@ -21,10 +21,12 @@
  *
  */
 
-class AP_AHRS_DCM : public AP_AHRS {
+#include "AP_AHRS.h"
+
+class AP_AHRS_DCM : public AP_AHRS_Backend {
 public:
     AP_AHRS_DCM()
-        : AP_AHRS()
+        : AP_AHRS_Backend()
         , _error_rp(1.0f)
         , _error_yaw(1.0f)
         , _mag_earth(1, 0)
diff --git a/libraries/AP_AHRS/AP_AHRS_Logging.cpp b/libraries/AP_AHRS/AP_AHRS_Logging.cpp
index 532a02699d..89b205f77a 100644
--- a/libraries/AP_AHRS/AP_AHRS_Logging.cpp
+++ b/libraries/AP_AHRS/AP_AHRS_Logging.cpp
@@ -6,7 +6,7 @@
 
 
 // Write an AHRS2 packet
-void AP_AHRS::Write_AHRS2() const
+void AP_AHRS_Backend::Write_AHRS2() const
 {
     Vector3f euler;
     struct Location loc;
@@ -32,7 +32,7 @@ void AP_AHRS::Write_AHRS2() const
 }
 
 // Write AOA and SSA
-void AP_AHRS::Write_AOA_SSA(void)
+void AP_AHRS_Backend::Write_AOA_SSA(void)
 {
     const struct log_AOA_SSA aoa_ssa{
         LOG_PACKET_HEADER_INIT(LOG_AOA_SSA_MSG),
@@ -45,7 +45,7 @@ void AP_AHRS::Write_AOA_SSA(void)
 }
 
 // Write an attitude packet
-void AP_AHRS::Write_Attitude(const Vector3f &targets) const
+void AP_AHRS_Backend::Write_Attitude(const Vector3f &targets) const
 {
     const struct log_Attitude pkt{
         LOG_PACKET_HEADER_INIT(LOG_ATTITUDE_MSG),
@@ -63,7 +63,7 @@ void AP_AHRS::Write_Attitude(const Vector3f &targets) const
     AP::logger().WriteBlock(&pkt, sizeof(pkt));
 }
 
-void AP_AHRS::Write_Origin(uint8_t origin_type, const Location &loc) const
+void AP_AHRS_Backend::Write_Origin(uint8_t origin_type, const Location &loc) const
 {
     const struct log_ORGN pkt{
         LOG_PACKET_HEADER_INIT(LOG_ORGN_MSG),
@@ -77,7 +77,7 @@ void AP_AHRS::Write_Origin(uint8_t origin_type, const Location &loc) const
 }
 
 // Write a POS packet
-void AP_AHRS::Write_POS() const
+void AP_AHRS_Backend::Write_POS() const
 {
     Location loc;
     if (!get_position(loc)) {
diff --git a/libraries/AP_AHRS/AP_AHRS_NavEKF.cpp b/libraries/AP_AHRS/AP_AHRS_NavEKF.cpp
index 9e2b43279d..54628459e0 100644
--- a/libraries/AP_AHRS/AP_AHRS_NavEKF.cpp
+++ b/libraries/AP_AHRS/AP_AHRS_NavEKF.cpp
@@ -37,19 +37,24 @@
 extern const AP_HAL::HAL& hal;
 
 // constructor
-AP_AHRS_NavEKF::AP_AHRS_NavEKF(uint8_t flags) :
+AP_AHRS::AP_AHRS(uint8_t flags) :
     AP_AHRS_DCM(),
     _ekf_flags(flags)
 {
+    _singleton = this;
+
+    // load default values from var_info table
+    AP_Param::setup_object_defaults(this, var_info);
+
 #if APM_BUILD_TYPE(APM_BUILD_ArduCopter) || APM_BUILD_TYPE(APM_BUILD_ArduSub)
     // Copter and Sub force the use of EKF
-    _ekf_flags |= AP_AHRS_NavEKF::FLAG_ALWAYS_USE_EKF;
+    _ekf_flags |= AP_AHRS::FLAG_ALWAYS_USE_EKF;
 #endif
     _dcm_matrix.identity();
 }
 
 // init sets up INS board orientation
-void AP_AHRS_NavEKF::init()
+void AP_AHRS::init()
 {
     // EKF1 is no longer supported - handle case where it is selected
     if (_ekf_type.get() == 1) {
@@ -74,7 +79,7 @@ void AP_AHRS_NavEKF::init()
 }
 
 // return the smoothed gyro vector corrected for drift
-const Vector3f &AP_AHRS_NavEKF::get_gyro(void) const
+const Vector3f &AP_AHRS::get_gyro(void) const
 {
     if (active_EKF_type() == EKFType::NONE) {
         return AP_AHRS_DCM::get_gyro();
@@ -82,7 +87,7 @@ const Vector3f &AP_AHRS_NavEKF::get_gyro(void) const
     return _gyro_estimate;
 }
 
-const Matrix3f &AP_AHRS_NavEKF::get_rotation_body_to_ned(void) const
+const Matrix3f &AP_AHRS::get_rotation_body_to_ned(void) const
 {
     if (active_EKF_type() == EKFType::NONE) {
         return AP_AHRS_DCM::get_rotation_body_to_ned();
@@ -90,7 +95,7 @@ const Matrix3f &AP_AHRS_NavEKF::get_rotation_body_to_ned(void) const
     return _dcm_matrix;
 }
 
-const Vector3f &AP_AHRS_NavEKF::get_gyro_drift(void) const
+const Vector3f &AP_AHRS::get_gyro_drift(void) const
 {
     if (active_EKF_type() == EKFType::NONE) {
         return AP_AHRS_DCM::get_gyro_drift();
@@ -100,7 +105,7 @@ const Vector3f &AP_AHRS_NavEKF::get_gyro_drift(void) const
 
 // reset the current gyro drift estimate
 //  should be called if gyro offsets are recalculated
-void AP_AHRS_NavEKF::reset_gyro_drift(void)
+void AP_AHRS::reset_gyro_drift(void)
 {
     // support locked access functions to AHRS data
     WITH_SEMAPHORE(_rsem);
@@ -117,7 +122,7 @@ void AP_AHRS_NavEKF::reset_gyro_drift(void)
 #endif
 }
 
-void AP_AHRS_NavEKF::update(bool skip_ins_update)
+void AP_AHRS::update(bool skip_ins_update)
 {
     // support locked access functions to AHRS data
     WITH_SEMAPHORE(_rsem);
@@ -209,7 +214,7 @@ void AP_AHRS_NavEKF::update(bool skip_ins_update)
     }
 }
 
-void AP_AHRS_NavEKF::update_DCM(bool skip_ins_update)
+void AP_AHRS::update_DCM(bool skip_ins_update)
 {
     // we need to restore the old DCM attitude values as these are
     // used internally in DCM to calculate error values for gyro drift
@@ -226,7 +231,7 @@ void AP_AHRS_NavEKF::update_DCM(bool skip_ins_update)
 }
 
 #if HAL_NAVEKF2_AVAILABLE
-void AP_AHRS_NavEKF::update_EKF2(void)
+void AP_AHRS::update_EKF2(void)
 {
     if (!_ekf2_started) {
         // wait 1 second for DCM to output a valid tilt error estimate
@@ -307,7 +312,7 @@ void AP_AHRS_NavEKF::update_EKF2(void)
 #endif
 
 #if HAL_NAVEKF3_AVAILABLE
-void AP_AHRS_NavEKF::update_EKF3(void)
+void AP_AHRS::update_EKF3(void)
 {
     if (!_ekf3_started) {
         // wait 1 second for DCM to output a valid tilt error estimate
@@ -389,7 +394,7 @@ void AP_AHRS_NavEKF::update_EKF3(void)
 #endif
 
 #if CONFIG_HAL_BOARD == HAL_BOARD_SITL
-void AP_AHRS_NavEKF::update_SITL(void)
+void AP_AHRS::update_SITL(void)
 {
     if (_sitl == nullptr) {
         _sitl = AP::sitl();
@@ -449,7 +454,7 @@ void AP_AHRS_NavEKF::update_SITL(void)
 #endif // CONFIG_HAL_BOARD
 
 #if HAL_EXTERNAL_AHRS_ENABLED
-void AP_AHRS_NavEKF::update_external(void)
+void AP_AHRS::update_external(void)
 {
     AP::externalAHRS().update();
 
@@ -479,7 +484,7 @@ void AP_AHRS_NavEKF::update_external(void)
 #endif // HAL_EXTERNAL_AHRS_ENABLED
 
 // accelerometer values in the earth frame in m/s/s
-const Vector3f &AP_AHRS_NavEKF::get_accel_ef(uint8_t i) const
+const Vector3f &AP_AHRS::get_accel_ef(uint8_t i) const
 {
     if (active_EKF_type() == EKFType::NONE) {
         return AP_AHRS_DCM::get_accel_ef(i);
@@ -488,7 +493,7 @@ const Vector3f &AP_AHRS_NavEKF::get_accel_ef(uint8_t i) const
 }
 
 // blended accelerometer values in the earth frame in m/s/s
-const Vector3f &AP_AHRS_NavEKF::get_accel_ef_blended(void) const
+const Vector3f &AP_AHRS::get_accel_ef_blended(void) const
 {
     if (active_EKF_type() == EKFType::NONE) {
         return AP_AHRS_DCM::get_accel_ef_blended();
@@ -496,7 +501,7 @@ const Vector3f &AP_AHRS_NavEKF::get_accel_ef_blended(void) const
     return _accel_ef_ekf_blended;
 }
 
-void AP_AHRS_NavEKF::reset(bool recover_eulers)
+void AP_AHRS::reset(bool recover_eulers)
 {
     // support locked access functions to AHRS data
     WITH_SEMAPHORE(_rsem);
@@ -516,7 +521,7 @@ void AP_AHRS_NavEKF::reset(bool recover_eulers)
 }
 
 // dead-reckoning support
-bool AP_AHRS_NavEKF::get_position(struct Location &loc) const
+bool AP_AHRS::get_position(struct Location &loc) const
 {
     switch (active_EKF_type()) {
     case EKFType::NONE:
@@ -567,18 +572,18 @@ bool AP_AHRS_NavEKF::get_position(struct Location &loc) const
 }
 
 // status reporting of estimated errors
-float AP_AHRS_NavEKF::get_error_rp(void) const
+float AP_AHRS::get_error_rp(void) const
 {
     return AP_AHRS_DCM::get_error_rp();
 }
 
-float AP_AHRS_NavEKF::get_error_yaw(void) const
+float AP_AHRS::get_error_yaw(void) const
 {
     return AP_AHRS_DCM::get_error_yaw();
 }
 
 // return a wind estimation vector, in m/s
-Vector3f AP_AHRS_NavEKF::wind_estimate(void) const
+Vector3f AP_AHRS::wind_estimate(void) const
 {
     Vector3f wind;
     switch (active_EKF_type()) {
@@ -616,7 +621,7 @@ Vector3f AP_AHRS_NavEKF::wind_estimate(void) const
 
 // return an airspeed estimate if available. return true
 // if we have an estimate
-bool AP_AHRS_NavEKF::airspeed_estimate(float &airspeed_ret) const
+bool AP_AHRS::airspeed_estimate(float &airspeed_ret) const
 {
     bool ret = false;
     if (airspeed_sensor_enabled()) {
@@ -688,7 +693,7 @@ bool AP_AHRS_NavEKF::airspeed_estimate(float &airspeed_ret) const
 
 // return estimate of true airspeed vector in body frame in m/s
 // returns false if estimate is unavailable
-bool AP_AHRS_NavEKF::airspeed_vector_true(Vector3f &vec) const
+bool AP_AHRS::airspeed_vector_true(Vector3f &vec) const
 {
     switch (active_EKF_type()) {
     case EKFType::NONE:
@@ -717,7 +722,7 @@ bool AP_AHRS_NavEKF::airspeed_vector_true(Vector3f &vec) const
 }
 
 // true if compass is being used
-bool AP_AHRS_NavEKF::use_compass(void)
+bool AP_AHRS::use_compass(void)
 {
     switch (active_EKF_type()) {
     case EKFType::NONE:
@@ -747,7 +752,7 @@ bool AP_AHRS_NavEKF::use_compass(void)
 }
 
 // return the quaternion defining the rotation from NED to XYZ (body) axes
-bool AP_AHRS_NavEKF::get_quaternion(Quaternion &quat) const
+bool AP_AHRS::get_quaternion(Quaternion &quat) const
 {
     switch (active_EKF_type()) {
     case EKFType::NONE:
@@ -782,7 +787,7 @@ bool AP_AHRS_NavEKF::get_quaternion(Quaternion &quat) const
 }
 
 // return secondary attitude solution if available, as eulers in radians
-bool AP_AHRS_NavEKF::get_secondary_attitude(Vector3f &eulers) const
+bool AP_AHRS::get_secondary_attitude(Vector3f &eulers) const
 {
     EKFType secondary_ekf_type;
     if (!get_secondary_EKF_type(secondary_ekf_type)) {
@@ -835,7 +840,7 @@ bool AP_AHRS_NavEKF::get_secondary_attitude(Vector3f &eulers) const
 
 
 // return secondary attitude solution if available, as quaternion
-bool AP_AHRS_NavEKF::get_secondary_quaternion(Quaternion &quat) const
+bool AP_AHRS::get_secondary_quaternion(Quaternion &quat) const
 {
     EKFType secondary_ekf_type;
     if (!get_secondary_EKF_type(secondary_ekf_type)) {
@@ -881,7 +886,7 @@ bool AP_AHRS_NavEKF::get_secondary_quaternion(Quaternion &quat) const
 }
 
 // return secondary position solution if available
-bool AP_AHRS_NavEKF::get_secondary_position(struct Location &loc) const
+bool AP_AHRS::get_secondary_position(struct Location &loc) const
 {
     EKFType secondary_ekf_type;
     if (!get_secondary_EKF_type(secondary_ekf_type)) {
@@ -927,7 +932,7 @@ bool AP_AHRS_NavEKF::get_secondary_position(struct Location &loc) const
 }
 
 // EKF has a better ground speed vector estimate
-Vector2f AP_AHRS_NavEKF::groundspeed_vector(void)
+Vector2f AP_AHRS::groundspeed_vector(void)
 {
     Vector3f vec;
 
@@ -968,7 +973,7 @@ Vector2f AP_AHRS_NavEKF::groundspeed_vector(void)
 // set the EKF's origin location in 10e7 degrees.  This should only
 // be called when the EKF has no absolute position reference (i.e. GPS)
 // from which to decide the origin on its own
-bool AP_AHRS_NavEKF::set_origin(const Location &loc)
+bool AP_AHRS::set_origin(const Location &loc)
 {
     WITH_SEMAPHORE(_rsem);
 #if HAL_NAVEKF2_AVAILABLE
@@ -1010,14 +1015,14 @@ bool AP_AHRS_NavEKF::set_origin(const Location &loc)
 }
 
 // return true if inertial navigation is active
-bool AP_AHRS_NavEKF::have_inertial_nav(void) const
+bool AP_AHRS::have_inertial_nav(void) const
 {
     return active_EKF_type() != EKFType::NONE;
 }
 
 // return a ground velocity in meters/second, North/East/Down
 // order. Must only be called if have_inertial_nav() is true
-bool AP_AHRS_NavEKF::get_velocity_NED(Vector3f &vec) const
+bool AP_AHRS::get_velocity_NED(Vector3f &vec) const
 {
     switch (active_EKF_type()) {
     case EKFType::NONE:
@@ -1054,7 +1059,7 @@ bool AP_AHRS_NavEKF::get_velocity_NED(Vector3f &vec) const
 }
 
 // returns the expected NED magnetic field
-bool AP_AHRS_NavEKF::get_mag_field_NED(Vector3f &vec) const
+bool AP_AHRS::get_mag_field_NED(Vector3f &vec) const
 {
     switch (active_EKF_type()) {
     case EKFType::NONE:
@@ -1085,7 +1090,7 @@ bool AP_AHRS_NavEKF::get_mag_field_NED(Vector3f &vec) const
 }
 
 // returns the estimated magnetic field offsets in body frame
-bool AP_AHRS_NavEKF::get_mag_field_correction(Vector3f &vec) const
+bool AP_AHRS::get_mag_field_correction(Vector3f &vec) const
 {
     switch (active_EKF_type()) {
     case EKFType::NONE:
@@ -1118,7 +1123,7 @@ bool AP_AHRS_NavEKF::get_mag_field_correction(Vector3f &vec) const
 
 // Get a derivative of the vertical position which is kinematically consistent with the vertical position is required by some control loops.
 // This is different to the vertical velocity from the EKF which is not always consistent with the verical position due to the various errors that are being corrected for.
-bool AP_AHRS_NavEKF::get_vert_pos_rate(float &velocity) const
+bool AP_AHRS::get_vert_pos_rate(float &velocity) const
 {
     switch (active_EKF_type()) {
     case EKFType::NONE:
@@ -1156,7 +1161,7 @@ bool AP_AHRS_NavEKF::get_vert_pos_rate(float &velocity) const
 }
 
 // get latest height above ground level estimate in metres and a validity flag
-bool AP_AHRS_NavEKF::get_hagl(float &height) const
+bool AP_AHRS::get_hagl(float &height) const
 {
     switch (active_EKF_type()) {
     case EKFType::NONE:
@@ -1194,7 +1199,7 @@ bool AP_AHRS_NavEKF::get_hagl(float &height) const
 
 // return a relative ground position to the origin in meters
 // North/East/Down order.
-bool AP_AHRS_NavEKF::get_relative_position_NED_origin(Vector3f &vec) const
+bool AP_AHRS::get_relative_position_NED_origin(Vector3f &vec) const
 {
     switch (active_EKF_type()) {
     case EKFType::NONE:
@@ -1268,7 +1273,7 @@ bool AP_AHRS_NavEKF::get_relative_position_NED_origin(Vector3f &vec) const
 
 // return a relative ground position to the home in meters
 // North/East/Down order.
-bool AP_AHRS_NavEKF::get_relative_position_NED_home(Vector3f &vec) const
+bool AP_AHRS::get_relative_position_NED_home(Vector3f &vec) const
 {
     Location originLLH;
     Vector3f originNED;
@@ -1287,7 +1292,7 @@ bool AP_AHRS_NavEKF::get_relative_position_NED_home(Vector3f &vec) const
 
 // write a relative ground position estimate to the origin in meters, North/East order
 // return true if estimate is valid
-bool AP_AHRS_NavEKF::get_relative_position_NE_origin(Vector2f &posNE) const
+bool AP_AHRS::get_relative_position_NE_origin(Vector2f &posNE) const
 {
     switch (active_EKF_type()) {
     case EKFType::NONE:
@@ -1336,7 +1341,7 @@ bool AP_AHRS_NavEKF::get_relative_position_NE_origin(Vector2f &posNE) const
 
 // return a relative ground position to the home in meters
 // North/East order.
-bool AP_AHRS_NavEKF::get_relative_position_NE_home(Vector2f &posNE) const
+bool AP_AHRS::get_relative_position_NE_home(Vector2f &posNE) const
 {
     Location originLLH;
     Vector2f originNE;
@@ -1357,7 +1362,7 @@ bool AP_AHRS_NavEKF::get_relative_position_NE_home(Vector2f &posNE) const
 
 // write a relative ground position to the origin in meters, Down
 // return true if the estimate is valid
-bool AP_AHRS_NavEKF::get_relative_position_D_origin(float &posD) const
+bool AP_AHRS::get_relative_position_D_origin(float &posD) const
 {
     switch (active_EKF_type()) {
     case EKFType::NONE:
@@ -1409,7 +1414,7 @@ bool AP_AHRS_NavEKF::get_relative_position_D_origin(float &posD) const
 
 // write a relative ground position to home in meters, Down
 // will use the barometer if the EKF isn't available
-void AP_AHRS_NavEKF::get_relative_position_D_home(float &posD) const
+void AP_AHRS::get_relative_position_D_home(float &posD) const
 {
     Location originLLH;
     float originD;
@@ -1426,7 +1431,7 @@ void AP_AHRS_NavEKF::get_relative_position_D_home(float &posD) const
   canonicalise _ekf_type, forcing it to be 0, 2 or 3
   type 1 has been deprecated
  */
-AP_AHRS_NavEKF::EKFType AP_AHRS_NavEKF::ekf_type(void) const
+AP_AHRS::EKFType AP_AHRS::ekf_type(void) const
 {
     EKFType type = (EKFType)_ekf_type.get();
     switch (type) {
@@ -1468,7 +1473,7 @@ AP_AHRS_NavEKF::EKFType AP_AHRS_NavEKF::ekf_type(void) const
 #endif
 }
 
-AP_AHRS_NavEKF::EKFType AP_AHRS_NavEKF::active_EKF_type(void) const
+AP_AHRS::EKFType AP_AHRS::active_EKF_type(void) const
 {
     EKFType ret = EKFType::NONE;
 
@@ -1605,7 +1610,7 @@ AP_AHRS_NavEKF::EKFType AP_AHRS_NavEKF::active_EKF_type(void) const
 }
 
 // get secondary EKF type.  returns false if no secondary (i.e. only using DCM)
-bool AP_AHRS_NavEKF::get_secondary_EKF_type(EKFType &secondary_ekf_type) const
+bool AP_AHRS::get_secondary_EKF_type(EKFType &secondary_ekf_type) const
 {
 
     switch (active_EKF_type()) {
@@ -1655,7 +1660,7 @@ bool AP_AHRS_NavEKF::get_secondary_EKF_type(EKFType &secondary_ekf_type) const
 /*
   check if the AHRS subsystem is healthy
 */
-bool AP_AHRS_NavEKF::healthy(void) const
+bool AP_AHRS::healthy(void) const
 {
     // If EKF is started we switch away if it reports unhealthy. This could be due to bad
     // sensor data. If EKF reversion is inhibited, we only switch across if the EKF encounters
@@ -1713,7 +1718,7 @@ bool AP_AHRS_NavEKF::healthy(void) const
 
 // returns false if we fail arming checks, in which case the buffer will be populated with a failure message
 // requires_position should be true if horizontal position configuration should be checked
-bool AP_AHRS_NavEKF::pre_arm_check(bool requires_position, char *failure_msg, uint8_t failure_msg_len) const
+bool AP_AHRS::pre_arm_check(bool requires_position, char *failure_msg, uint8_t failure_msg_len) const
 {
     bool ret = true;
     if (!healthy()) {
@@ -1760,7 +1765,7 @@ bool AP_AHRS_NavEKF::pre_arm_check(bool requires_position, char *failure_msg, ui
 }
 
 // true if the AHRS has completed initialisation
-bool AP_AHRS_NavEKF::initialised(void) const
+bool AP_AHRS::initialised(void) const
 {
     switch (ekf_type()) {
     case EKFType::NONE:
@@ -1791,7 +1796,7 @@ bool AP_AHRS_NavEKF::initialised(void) const
 };
 
 // get_filter_status : returns filter status as a series of flags
-bool AP_AHRS_NavEKF::get_filter_status(nav_filter_status &status) const
+bool AP_AHRS::get_filter_status(nav_filter_status &status) const
 {
     switch (ekf_type()) {
     case EKFType::NONE:
@@ -1834,7 +1839,7 @@ bool AP_AHRS_NavEKF::get_filter_status(nav_filter_status &status) const
 }
 
 // write optical flow data to EKF
-void  AP_AHRS_NavEKF::writeOptFlowMeas(const uint8_t rawFlowQuality, const Vector2f &rawFlowRates, const Vector2f &rawGyroRates, const uint32_t msecFlowMeas, const Vector3f &posOffset)
+void  AP_AHRS::writeOptFlowMeas(const uint8_t rawFlowQuality, const Vector2f &rawFlowRates, const Vector2f &rawGyroRates, const uint32_t msecFlowMeas, const Vector3f &posOffset)
 {
 #if HAL_NAVEKF2_AVAILABLE
     EKF2.writeOptFlowMeas(rawFlowQuality, rawFlowRates, rawGyroRates, msecFlowMeas, posOffset);
@@ -1845,7 +1850,7 @@ void  AP_AHRS_NavEKF::writeOptFlowMeas(const uint8_t rawFlowQuality, const Vecto
 }
 
 // write body frame odometry measurements to the EKF
-void  AP_AHRS_NavEKF::writeBodyFrameOdom(float quality, const Vector3f &delPos, const Vector3f &delAng, float delTime, uint32_t timeStamp_ms, uint16_t delay_ms, const Vector3f &posOffset)
+void  AP_AHRS::writeBodyFrameOdom(float quality, const Vector3f &delPos, const Vector3f &delAng, float delTime, uint32_t timeStamp_ms, uint16_t delay_ms, const Vector3f &posOffset)
 {
 #if HAL_NAVEKF3_AVAILABLE
     EKF3.writeBodyFrameOdom(quality, delPos, delAng, delTime, timeStamp_ms, delay_ms, posOffset);
@@ -1853,7 +1858,7 @@ void  AP_AHRS_NavEKF::writeBodyFrameOdom(float quality, const Vector3f &delPos,
 }
 
 // Write position and quaternion data from an external navigation system
-void AP_AHRS_NavEKF::writeExtNavData(const Vector3f &pos, const Quaternion &quat, float posErr, float angErr, uint32_t timeStamp_ms, uint16_t delay_ms, uint32_t resetTime_ms)
+void AP_AHRS::writeExtNavData(const Vector3f &pos, const Quaternion &quat, float posErr, float angErr, uint32_t timeStamp_ms, uint16_t delay_ms, uint32_t resetTime_ms)
 {
 #if HAL_NAVEKF2_AVAILABLE
     EKF2.writeExtNavData(pos, quat, posErr, angErr, timeStamp_ms, delay_ms, resetTime_ms);
@@ -1864,7 +1869,7 @@ void AP_AHRS_NavEKF::writeExtNavData(const Vector3f &pos, const Quaternion &quat
 }
 
 // Writes the default equivalent airspeed and 1-sigma uncertainty in m/s to be used in forward flight if a measured airspeed is required and not available.
-void AP_AHRS_NavEKF::writeDefaultAirSpeed(float airspeed, float uncertainty)
+void AP_AHRS::writeDefaultAirSpeed(float airspeed, float uncertainty)
 {
 #if HAL_NAVEKF2_AVAILABLE
     EKF2.writeDefaultAirSpeed(airspeed);
@@ -1875,7 +1880,7 @@ void AP_AHRS_NavEKF::writeDefaultAirSpeed(float airspeed, float uncertainty)
 }
 
 // Write velocity data from an external navigation system
-void AP_AHRS_NavEKF::writeExtNavVelData(const Vector3f &vel, float err, uint32_t timeStamp_ms, uint16_t delay_ms)
+void AP_AHRS::writeExtNavVelData(const Vector3f &vel, float err, uint32_t timeStamp_ms, uint16_t delay_ms)
 {
 #if HAL_NAVEKF2_AVAILABLE
     EKF2.writeExtNavVelData(vel, err, timeStamp_ms, delay_ms);
@@ -1886,7 +1891,7 @@ void AP_AHRS_NavEKF::writeExtNavVelData(const Vector3f &vel, float err, uint32_t
 }
 
 // get speed limit
-void AP_AHRS_NavEKF::getEkfControlLimits(float &ekfGndSpdLimit, float &ekfNavVelGainScaler) const
+void AP_AHRS::getEkfControlLimits(float &ekfGndSpdLimit, float &ekfNavVelGainScaler) const
 {
     switch (ekf_type()) {
     case EKFType::NONE:
@@ -1921,7 +1926,7 @@ void AP_AHRS_NavEKF::getEkfControlLimits(float &ekfGndSpdLimit, float &ekfNavVel
 
 // get compass offset estimates
 // true if offsets are valid
-bool AP_AHRS_NavEKF::getMagOffsets(uint8_t mag_idx, Vector3f &magOffsets) const
+bool AP_AHRS::getMagOffsets(uint8_t mag_idx, Vector3f &magOffsets) const
 {
     switch (ekf_type()) {
     case EKFType::NONE:
@@ -1952,7 +1957,7 @@ bool AP_AHRS_NavEKF::getMagOffsets(uint8_t mag_idx, Vector3f &magOffsets) const
 }
 
 // Retrieves the NED delta velocity corrected
-void AP_AHRS_NavEKF::getCorrectedDeltaVelocityNED(Vector3f& ret, float& dt) const
+void AP_AHRS::getCorrectedDeltaVelocityNED(Vector3f& ret, float& dt) const
 {
     int8_t imu_idx = -1;
     Vector3f accel_bias;
@@ -1992,7 +1997,7 @@ void AP_AHRS_NavEKF::getCorrectedDeltaVelocityNED(Vector3f& ret, float& dt) cons
 }
 
 // check all cores providing consistent attitudes for prearm checks
-bool AP_AHRS_NavEKF::attitudes_consistent(char *failure_msg, const uint8_t failure_msg_len) const
+bool AP_AHRS::attitudes_consistent(char *failure_msg, const uint8_t failure_msg_len) const
 {
     // get primary attitude source's attitude as quaternion
     Quaternion primary_quat;
@@ -2085,7 +2090,7 @@ bool AP_AHRS_NavEKF::attitudes_consistent(char *failure_msg, const uint8_t failu
 
 // return the amount of yaw angle change due to the last yaw angle reset in radians
 // returns the time of the last yaw angle reset or 0 if no reset has ever occurred
-uint32_t AP_AHRS_NavEKF::getLastYawResetAngle(float &yawAng)
+uint32_t AP_AHRS::getLastYawResetAngle(float &yawAng)
 {
     switch (ekf_type()) {
 
@@ -2116,7 +2121,7 @@ uint32_t AP_AHRS_NavEKF::getLastYawResetAngle(float &yawAng)
 
 // return the amount of NE position change in metres due to the last reset
 // returns the time of the last reset or 0 if no reset has ever occurred
-uint32_t AP_AHRS_NavEKF::getLastPosNorthEastReset(Vector2f &pos)
+uint32_t AP_AHRS::getLastPosNorthEastReset(Vector2f &pos)
 {
     switch (ekf_type()) {
 
@@ -2147,7 +2152,7 @@ uint32_t AP_AHRS_NavEKF::getLastPosNorthEastReset(Vector2f &pos)
 
 // return the amount of NE velocity change in metres/sec due to the last reset
 // returns the time of the last reset or 0 if no reset has ever occurred
-uint32_t AP_AHRS_NavEKF::getLastVelNorthEastReset(Vector2f &vel) const
+uint32_t AP_AHRS::getLastVelNorthEastReset(Vector2f &vel) const
 {
     switch (ekf_type()) {
 
@@ -2179,7 +2184,7 @@ uint32_t AP_AHRS_NavEKF::getLastVelNorthEastReset(Vector2f &vel) const
 
 // return the amount of vertical position change due to the last reset in meters
 // returns the time of the last reset or 0 if no reset has ever occurred
-uint32_t AP_AHRS_NavEKF::getLastPosDownReset(float &posDelta)
+uint32_t AP_AHRS::getLastPosDownReset(float &posDelta)
 {
     switch (ekf_type()) {
     case EKFType::NONE:
@@ -2212,7 +2217,7 @@ uint32_t AP_AHRS_NavEKF::getLastPosDownReset(float &posDelta)
 // Adjusts the EKf origin height so that the EKF height + origin height is the same as before
 // Returns true if the height datum reset has been performed
 // If using a range finder for height no reset is performed and it returns false
-bool AP_AHRS_NavEKF::resetHeightDatum(void)
+bool AP_AHRS::resetHeightDatum(void)
 {
     // support locked access functions to AHRS data
     WITH_SEMAPHORE(_rsem);
@@ -2257,7 +2262,7 @@ bool AP_AHRS_NavEKF::resetHeightDatum(void)
 }
 
 // send a EKF_STATUS_REPORT for current EKF
-void AP_AHRS_NavEKF::send_ekf_status_report(mavlink_channel_t chan) const
+void AP_AHRS::send_ekf_status_report(mavlink_channel_t chan) const
 {
     switch (ekf_type()) {
     case EKFType::NONE:
@@ -2308,7 +2313,7 @@ void AP_AHRS_NavEKF::send_ekf_status_report(mavlink_channel_t chan) const
 // passes a reference to the location of the inertial navigation origin
 // in WGS-84 coordinates
 // returns a boolean true when the inertial navigation origin has been set
-bool AP_AHRS_NavEKF::get_origin(Location &ret) const
+bool AP_AHRS::get_origin(Location &ret) const
 {
     switch (ekf_type()) {
     case EKFType::NONE:
@@ -2352,7 +2357,7 @@ bool AP_AHRS_NavEKF::get_origin(Location &ret) const
 // get_hgt_ctrl_limit - get maximum height to be observed by the control loops in metres and a validity flag
 // this is used to limit height during optical flow navigation
 // it will return false when no limiting is required
-bool AP_AHRS_NavEKF::get_hgt_ctrl_limit(float& limit) const
+bool AP_AHRS::get_hgt_ctrl_limit(float& limit) const
 {
     switch (ekf_type()) {
     case EKFType::NONE:
@@ -2384,7 +2389,7 @@ bool AP_AHRS_NavEKF::get_hgt_ctrl_limit(float& limit) const
 
 // Set to true if the terrain underneath is stable enough to be used as a height reference
 // this is not related to terrain following
-void AP_AHRS_NavEKF::set_terrain_hgt_stable(bool stable)
+void AP_AHRS::set_terrain_hgt_stable(bool stable)
 {
     // avoid repeatedly setting variable in NavEKF objects to prevent
     // spurious event logging
@@ -2414,7 +2419,7 @@ void AP_AHRS_NavEKF::set_terrain_hgt_stable(bool stable)
 
 // get_location - updates the provided location with the latest calculated location
 //  returns true on success (i.e. the EKF knows it's latest position), false on failure
-bool AP_AHRS_NavEKF::get_location(struct Location &loc) const
+bool AP_AHRS::get_location(struct Location &loc) const
 {
     switch (ekf_type()) {
     case EKFType::NONE:
@@ -2446,7 +2451,7 @@ bool AP_AHRS_NavEKF::get_location(struct Location &loc) const
 
 // return the innovations for the primariy EKF
 // boolean false is returned if innovations are not available
-bool AP_AHRS_NavEKF::get_innovations(Vector3f &velInnov, Vector3f &posInnov, Vector3f &magInnov, float &tasInnov, float &yawInnov) const
+bool AP_AHRS::get_innovations(Vector3f &velInnov, Vector3f &posInnov, Vector3f &magInnov, float &tasInnov, float &yawInnov) const
 {
     switch (ekf_type()) {
     case EKFType::NONE:
@@ -2488,7 +2493,7 @@ bool AP_AHRS_NavEKF::get_innovations(Vector3f &velInnov, Vector3f &posInnov, Vec
 // indicates prefect consistency between the measurement and the EKF solution and a value of of 1 is the maximum
 // inconsistency that will be accpeted by the filter
 // boolean false is returned if variances are not available
-bool AP_AHRS_NavEKF::get_variances(float &velVar, float &posVar, float &hgtVar, Vector3f &magVar, float &tasVar) const
+bool AP_AHRS::get_variances(float &velVar, float &posVar, float &hgtVar, Vector3f &magVar, float &tasVar) const
 {
     switch (ekf_type()) {
     case EKFType::NONE:
@@ -2532,7 +2537,7 @@ bool AP_AHRS_NavEKF::get_variances(float &velVar, float &posVar, float &hgtVar,
 
 // get a source's velocity innovations.  source should be from 0 to 7 (see AP_NavEKF_Source::SourceXY)
 // returns true on success and results are placed in innovations and variances arguments
-bool AP_AHRS_NavEKF::get_vel_innovations_and_variances_for_source(uint8_t source, Vector3f &innovations, Vector3f &variances) const
+bool AP_AHRS::get_vel_innovations_and_variances_for_source(uint8_t source, Vector3f &innovations, Vector3f &variances) const
 {
     switch (ekf_type()) {
     case EKFType::NONE:
@@ -2566,7 +2571,7 @@ bool AP_AHRS_NavEKF::get_vel_innovations_and_variances_for_source(uint8_t source
     return false;
 }
 
-bool AP_AHRS_NavEKF::getGpsGlitchStatus() const
+bool AP_AHRS::getGpsGlitchStatus() const
 {
     nav_filter_status ekf_status {};
     if (!get_filter_status(ekf_status)) {
@@ -2576,7 +2581,7 @@ bool AP_AHRS_NavEKF::getGpsGlitchStatus() const
 }
 
 //get the index of the active airspeed sensor, wrt the primary core
-uint8_t AP_AHRS_NavEKF::get_active_airspeed_index() const
+uint8_t AP_AHRS::get_active_airspeed_index() const
 {
 // we only have affinity for EKF3 as of now
 #if HAL_NAVEKF3_AVAILABLE
@@ -2593,7 +2598,7 @@ uint8_t AP_AHRS_NavEKF::get_active_airspeed_index() const
 }
 
 // get the index of the current primary IMU
-uint8_t AP_AHRS_NavEKF::get_primary_IMU_index() const
+uint8_t AP_AHRS::get_primary_IMU_index() const
 {
     int8_t imu = -1;
     switch (ekf_type()) {
@@ -2627,13 +2632,13 @@ uint8_t AP_AHRS_NavEKF::get_primary_IMU_index() const
 }
 
 // get earth-frame accel vector for primary IMU
-const Vector3f &AP_AHRS_NavEKF::get_accel_ef() const
+const Vector3f &AP_AHRS::get_accel_ef() const
 {
     return get_accel_ef(get_primary_accel_index());
 }
 
 // return the index of the primary core or -1 if no primary core selected
-int8_t AP_AHRS_NavEKF::get_primary_core_index() const
+int8_t AP_AHRS::get_primary_core_index() const
 {
     switch (active_EKF_type()) {
     case EKFType::NONE:
@@ -2663,7 +2668,7 @@ int8_t AP_AHRS_NavEKF::get_primary_core_index() const
 }
 
 // get the index of the current primary accelerometer sensor
-uint8_t AP_AHRS_NavEKF::get_primary_accel_index(void) const
+uint8_t AP_AHRS::get_primary_accel_index(void) const
 {
     if (ekf_type() != EKFType::NONE) {
         return get_primary_IMU_index();
@@ -2672,7 +2677,7 @@ uint8_t AP_AHRS_NavEKF::get_primary_accel_index(void) const
 }
 
 // get the index of the current primary gyro sensor
-uint8_t AP_AHRS_NavEKF::get_primary_gyro_index(void) const
+uint8_t AP_AHRS::get_primary_gyro_index(void) const
 {
     if (ekf_type() != EKFType::NONE) {
         return get_primary_IMU_index();
@@ -2681,7 +2686,7 @@ uint8_t AP_AHRS_NavEKF::get_primary_gyro_index(void) const
 }
 
 // see if EKF lane switching is possible to avoid EKF failsafe
-void AP_AHRS_NavEKF::check_lane_switch(void)
+void AP_AHRS::check_lane_switch(void)
 {
     switch (active_EKF_type()) {
     case EKFType::NONE:
@@ -2712,7 +2717,7 @@ void AP_AHRS_NavEKF::check_lane_switch(void)
 }
 
 // request EKF yaw reset to try and avoid the need for an EKF lane switch or failsafe
-void AP_AHRS_NavEKF::request_yaw_reset(void)
+void AP_AHRS::request_yaw_reset(void)
 {
     switch (active_EKF_type()) {
     case EKFType::NONE:
@@ -2743,14 +2748,14 @@ void AP_AHRS_NavEKF::request_yaw_reset(void)
 }
 
 // set position, velocity and yaw sources to either 0=primary, 1=secondary, 2=tertiary
-void AP_AHRS_NavEKF::set_posvelyaw_source_set(uint8_t source_set_idx)
+void AP_AHRS::set_posvelyaw_source_set(uint8_t source_set_idx)
 {
 #if HAL_NAVEKF3_AVAILABLE
     EKF3.setPosVelYawSourceSet(source_set_idx);
 #endif
 }
 
-void AP_AHRS_NavEKF::Log_Write()
+void AP_AHRS::Log_Write()
 {
 #if HAL_NAVEKF2_AVAILABLE
     EKF2.Log_Write();
@@ -2760,13 +2765,8 @@ void AP_AHRS_NavEKF::Log_Write()
 #endif
 }
 
-AP_AHRS_NavEKF &AP::ahrs_navekf()
-{
-    return static_cast<AP_AHRS_NavEKF&>(*AP_AHRS::get_singleton());
-}
-
 // check whether compass can be bypassed for arming check in case when external navigation data is available 
-bool AP_AHRS_NavEKF::is_ext_nav_used_for_yaw(void) const
+bool AP_AHRS::is_ext_nav_used_for_yaw(void) const
 {
     switch (active_EKF_type()) {
 #if HAL_NAVEKF2_AVAILABLE
@@ -2791,7 +2791,7 @@ bool AP_AHRS_NavEKF::is_ext_nav_used_for_yaw(void) const
 }
 
 // set and save the alt noise parameter value
-void AP_AHRS_NavEKF::set_alt_measurement_noise(float noise)
+void AP_AHRS::set_alt_measurement_noise(float noise)
 {
 #if HAL_NAVEKF2_AVAILABLE
     EKF2.set_baro_alt_noise(noise);
@@ -2800,3 +2800,16 @@ void AP_AHRS_NavEKF::set_alt_measurement_noise(float noise)
     EKF3.set_baro_alt_noise(noise);
 #endif
 }
+
+
+// singleton instance
+AP_AHRS *AP_AHRS::_singleton;
+
+namespace AP {
+
+AP_AHRS &ahrs()
+{
+    return *AP_AHRS::get_singleton();
+}
+
+}
diff --git a/libraries/AP_AHRS/AP_AHRS_NavEKF.h b/libraries/AP_AHRS/AP_AHRS_NavEKF.h
index 0160777846..1824c30cde 100644
--- a/libraries/AP_AHRS/AP_AHRS_NavEKF.h
+++ b/libraries/AP_AHRS/AP_AHRS_NavEKF.h
@@ -44,24 +44,34 @@
 #include <AP_NavEKF3/AP_NavEKF3.h>
 #include <AP_NavEKF/AP_Nav_Common.h>              // definitions shared by inertial and ekf nav filters
 
+#include "AP_AHRS_DCM.h"
+
+// forward declare view class
+class AP_AHRS_View;
 
 #define AP_AHRS_NAVEKF_SETTLE_TIME_MS 20000     // time in milliseconds the ekf needs to settle after being started
 
-class AP_AHRS_NavEKF : public AP_AHRS_DCM {
+class AP_AHRS : public AP_AHRS_DCM {
+    friend class AP_AHRS_View;
 public:
+
     enum Flags {
         FLAG_ALWAYS_USE_EKF = 0x1,
     };
 
     // Constructor
-    AP_AHRS_NavEKF(uint8_t flags = 0);
+    AP_AHRS(uint8_t flags = 0);
 
     // initialise
     void init(void) override;
 
     /* Do not allow copies */
-    AP_AHRS_NavEKF(const AP_AHRS_NavEKF &other) = delete;
-    AP_AHRS_NavEKF &operator=(const AP_AHRS_NavEKF&) = delete;
+    CLASS_NO_COPY(AP_AHRS);
+
+    // get singleton instance
+    static AP_AHRS *get_singleton() {
+        return _singleton;
+    }
 
     // return the smoothed gyro vector corrected for drift
     const Vector3f &get_gyro(void) const override;
@@ -303,7 +313,19 @@ public:
     NavEKF3 EKF3;
 #endif
 
+    // for holding parameters
+    static const struct AP_Param::GroupInfo var_info[];
+
+    // create a view
+    AP_AHRS_View *create_view(enum Rotation rotation, float pitch_trim_deg=0);
+
+protected:
+    // optional view class
+    AP_AHRS_View *_view;
+
 private:
+    static AP_AHRS *_singleton;
+
     enum class EKFType {
         NONE = 0
 #if HAL_NAVEKF3_AVAILABLE
@@ -377,3 +399,7 @@ private:
     void update_external(void);
 #endif    
 };
+
+namespace AP {
+    AP_AHRS &ahrs();
+};
diff --git a/libraries/AP_AHRS/examples/AHRS_Test/AHRS_Test.cpp b/libraries/AP_AHRS/examples/AHRS_Test/AHRS_Test.cpp
index 4f4f6ae747..521d6a7e29 100644
--- a/libraries/AP_AHRS/examples/AHRS_Test/AHRS_Test.cpp
+++ b/libraries/AP_AHRS/examples/AHRS_Test/AHRS_Test.cpp
@@ -25,7 +25,7 @@ static AP_Logger logger{logger_bitmask};
 
 class DummyVehicle : public AP_Vehicle {
 public:
-    AP_AHRS_NavEKF ahrs{AP_AHRS_NavEKF::FLAG_ALWAYS_USE_EKF};
+    AP_AHRS ahrs{AP_AHRS::FLAG_ALWAYS_USE_EKF};
     bool set_mode(const uint8_t new_mode, const ModeReason reason) override { return true; };
     uint8_t get_mode() const override { return 1; };
     void get_scheduler_tasks(const AP_Scheduler::Task *&tasks, uint8_t &task_count, uint32_t &log_bit) override {};
@@ -43,7 +43,7 @@ static DummyVehicle vehicle;
 
 // choose which AHRS system to use
 // AP_AHRS_DCM ahrs = AP_AHRS_DCM::create(barometer, gps);
-AP_AHRS_NavEKF &ahrs = vehicle.ahrs;
+auto &ahrs = vehicle.ahrs;
 
 void setup(void)
 {