diff --git a/libraries/AP_RPM/RPM_EFI.cpp b/libraries/AP_RPM/RPM_EFI.cpp
index 1cfa0ad011..82e126bf3c 100644
--- a/libraries/AP_RPM/RPM_EFI.cpp
+++ b/libraries/AP_RPM/RPM_EFI.cpp
@@ -13,19 +13,14 @@
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include <AP_HAL/AP_HAL.h>
-
-#include "RPM_EFI.h"
+#include "AP_RPM_config.h"
 
 #if AP_RPM_EFI_ENABLED
 
+#include "RPM_EFI.h"
+#include <AP_HAL/AP_HAL.h>
 #include <AP_EFI/AP_EFI.h>
 
-AP_RPM_EFI::AP_RPM_EFI(AP_RPM &_ap_rpm, uint8_t _instance, AP_RPM::RPM_State &_state) :
-    AP_RPM_Backend(_ap_rpm, _instance, _state)
-{
-}
-
 void AP_RPM_EFI::update(void)
 {
     AP_EFI *efi = AP::EFI();
diff --git a/libraries/AP_RPM/RPM_EFI.h b/libraries/AP_RPM/RPM_EFI.h
index 76710a3009..9d5ef49d25 100644
--- a/libraries/AP_RPM/RPM_EFI.h
+++ b/libraries/AP_RPM/RPM_EFI.h
@@ -14,7 +14,7 @@
  */
 #pragma once
 
-#include "AP_RPM.h"
+#include "AP_RPM_config.h"
 
 #if AP_RPM_EFI_ENABLED
 
@@ -23,13 +23,13 @@
 class AP_RPM_EFI : public AP_RPM_Backend
 {
 public:
+
     // constructor
-    AP_RPM_EFI(AP_RPM &ranger, uint8_t instance, AP_RPM::RPM_State &_state);
+    using AP_RPM_Backend::AP_RPM_Backend;
 
     // update state
     void update(void) override;
 
-private:
 };
 
 #endif
diff --git a/libraries/AP_RPM/RPM_ESC_Telem.cpp b/libraries/AP_RPM/RPM_ESC_Telem.cpp
index abb9b5f78a..ea44ea29e9 100644
--- a/libraries/AP_RPM/RPM_ESC_Telem.cpp
+++ b/libraries/AP_RPM/RPM_ESC_Telem.cpp
@@ -13,23 +13,13 @@
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include <AP_HAL/AP_HAL.h>
-#include <AP_ESC_Telem/AP_ESC_Telem.h>
-
-#include "RPM_ESC_Telem.h"
+#include "AP_RPM_config.h"
 
 #if AP_RPM_ESC_TELEM_ENABLED
 
-extern const AP_HAL::HAL& hal;
-
-/*
-   open the sensor in constructor
-*/
-AP_RPM_ESC_Telem::AP_RPM_ESC_Telem(AP_RPM &_ap_rpm, uint8_t _instance, AP_RPM::RPM_State &_state) :
-    AP_RPM_Backend(_ap_rpm, _instance, _state)
-{
-}
-
+#include <AP_ESC_Telem/AP_ESC_Telem.h>
+#include "RPM_ESC_Telem.h"
+#include <AP_HAL/AP_HAL.h>
 
 void AP_RPM_ESC_Telem::update(void)
 {
diff --git a/libraries/AP_RPM/RPM_ESC_Telem.h b/libraries/AP_RPM/RPM_ESC_Telem.h
index e8ef243871..f9ebb632db 100644
--- a/libraries/AP_RPM/RPM_ESC_Telem.h
+++ b/libraries/AP_RPM/RPM_ESC_Telem.h
@@ -14,16 +14,17 @@
  */
 #pragma once
 
-#include "AP_RPM.h"
-#include "RPM_Backend.h"
+#include "AP_RPM_config.h"
 
 #if AP_RPM_ESC_TELEM_ENABLED
 
+#include "RPM_Backend.h"
+
 class AP_RPM_ESC_Telem : public AP_RPM_Backend
 {
 public:
     // constructor
-    AP_RPM_ESC_Telem(AP_RPM &ranger, uint8_t instance, AP_RPM::RPM_State &_state);
+    using AP_RPM_Backend::AP_RPM_Backend;
 
     // update state
     void update(void) override;
diff --git a/libraries/AP_RPM/RPM_Generator.cpp b/libraries/AP_RPM/RPM_Generator.cpp
index 81b087f20f..0ed375d0cb 100644
--- a/libraries/AP_RPM/RPM_Generator.cpp
+++ b/libraries/AP_RPM/RPM_Generator.cpp
@@ -13,12 +13,12 @@
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include <AP_HAL/AP_HAL.h>
-
-#include "RPM_Generator.h"
+#include "AP_RPM_config.h"
 
 #if AP_RPM_GENERATOR_ENABLED
-extern const AP_HAL::HAL& hal;
+
+#include "RPM_Generator.h"
+#include <AP_Generator/AP_Generator.h>
 
 void AP_RPM_Generator::update(void)
 {
diff --git a/libraries/AP_RPM/RPM_Generator.h b/libraries/AP_RPM/RPM_Generator.h
index 627fc8ae9c..a9da14a121 100644
--- a/libraries/AP_RPM/RPM_Generator.h
+++ b/libraries/AP_RPM/RPM_Generator.h
@@ -14,12 +14,12 @@
  */
 #pragma once
 
-#include "AP_RPM.h"
-#include "RPM_Backend.h"
-#include <AP_Generator/AP_Generator.h>
+#include "AP_RPM_config.h"
 
 #if AP_RPM_GENERATOR_ENABLED
 
+#include "RPM_Backend.h"
+
 class AP_RPM_Generator : public AP_RPM_Backend
 {
 public:
diff --git a/libraries/AP_RPM/RPM_HarmonicNotch.cpp b/libraries/AP_RPM/RPM_HarmonicNotch.cpp
index e5dbbe766c..8fba549917 100644
--- a/libraries/AP_RPM/RPM_HarmonicNotch.cpp
+++ b/libraries/AP_RPM/RPM_HarmonicNotch.cpp
@@ -13,18 +13,15 @@
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include "RPM_HarmonicNotch.h"
+#include "AP_RPM_config.h"
 
 #if AP_RPM_HARMONICNOTCH_ENABLED
 
+#include "RPM_HarmonicNotch.h"
+
 #include <AP_HAL/AP_HAL.h>
 #include <AP_InertialSensor/AP_InertialSensor.h>
 
-AP_RPM_HarmonicNotch::AP_RPM_HarmonicNotch(AP_RPM &_ap_rpm, uint8_t _instance, AP_RPM::RPM_State &_state) :
-    AP_RPM_Backend(_ap_rpm, _instance, _state)
-{
-}
-
 void AP_RPM_HarmonicNotch::update(void)
 {
     const AP_InertialSensor& ins = AP::ins();
diff --git a/libraries/AP_RPM/RPM_HarmonicNotch.h b/libraries/AP_RPM/RPM_HarmonicNotch.h
index 81d13a4cfa..5ea617f30d 100644
--- a/libraries/AP_RPM/RPM_HarmonicNotch.h
+++ b/libraries/AP_RPM/RPM_HarmonicNotch.h
@@ -14,16 +14,17 @@
  */
 #pragma once
 
-#include "AP_RPM.h"
-#include "RPM_Backend.h"
+#include "AP_RPM_config.h"
 
 #if AP_RPM_HARMONICNOTCH_ENABLED
 
+#include "RPM_Backend.h"
+
 class AP_RPM_HarmonicNotch : public AP_RPM_Backend
 {
 public:
     // constructor
-    AP_RPM_HarmonicNotch(AP_RPM &ranger, uint8_t instance, AP_RPM::RPM_State &_state);
+    using AP_RPM_Backend::AP_RPM_Backend;
 
     // update state
     void update(void) override;
diff --git a/libraries/AP_RPM/RPM_Pin.cpp b/libraries/AP_RPM/RPM_Pin.cpp
index 8dc27fcac5..43d9443eb5 100644
--- a/libraries/AP_RPM/RPM_Pin.cpp
+++ b/libraries/AP_RPM/RPM_Pin.cpp
@@ -13,26 +13,20 @@
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include "RPM_Pin.h"
+#include "AP_RPM_config.h"
 
 #if AP_RPM_PIN_ENABLED
 
-#include <AP_HAL/AP_HAL.h>
+#include "RPM_Pin.h"
 
+#include <AP_HAL/AP_HAL.h>
 #include <AP_HAL/GPIO.h>
 #include <GCS_MAVLink/GCS.h>
+#include <AP_Math/AP_Math.h>
 
 extern const AP_HAL::HAL& hal;
 AP_RPM_Pin::IrqState AP_RPM_Pin::irq_state[RPM_MAX_INSTANCES];
 
-/* 
-   open the sensor in constructor
-*/
-AP_RPM_Pin::AP_RPM_Pin(AP_RPM &_ap_rpm, uint8_t instance, AP_RPM::RPM_State &_state) :
-	AP_RPM_Backend(_ap_rpm, instance, _state)
-{
-}
-
 /*
   handle interrupt on an instance
  */
diff --git a/libraries/AP_RPM/RPM_Pin.h b/libraries/AP_RPM/RPM_Pin.h
index e196eddc21..95c957f1f5 100644
--- a/libraries/AP_RPM/RPM_Pin.h
+++ b/libraries/AP_RPM/RPM_Pin.h
@@ -14,20 +14,19 @@
  */
 #pragma once
 
-#include "AP_RPM.h"
-
-#include "RPM_Backend.h"
+#include "AP_RPM_config.h"
 
 #if AP_RPM_PIN_ENABLED
 
+#include "RPM_Backend.h"
+
 #include <Filter/Filter.h>
-#include <AP_Math/AP_Math.h>
 
 class AP_RPM_Pin : public AP_RPM_Backend
 {
 public:
-    // constructor
-    AP_RPM_Pin(AP_RPM &ranger, uint8_t instance, AP_RPM::RPM_State &_state);
+
+    using AP_RPM_Backend::AP_RPM_Backend;
 
     // update state
     void update(void) override;