diff --git a/libraries/AP_Motors/AP_MotorsCoax.cpp b/libraries/AP_Motors/AP_MotorsCoax.cpp
index f2595a9279..4207bd26d5 100644
--- a/libraries/AP_Motors/AP_MotorsCoax.cpp
+++ b/libraries/AP_Motors/AP_MotorsCoax.cpp
@@ -88,23 +88,23 @@ void AP_MotorsCoax::set_update_rate( uint16_t speed_hz )
     uint32_t mask2 =
         1U << AP_MOTORS_MOT_3 |
         1U << AP_MOTORS_MOT_4 ;
-    hal.rcout->set_freq(mask2, _speed_hz);
+    rc_set_freq(mask2, _speed_hz);
 
     // set update rate for the two servos
     uint32_t mask =
       1U << AP_MOTORS_MOT_1 |
       1U << AP_MOTORS_MOT_2 ;
-    hal.rcout->set_freq(mask, _servo_speed);
+    rc_set_freq(mask, _servo_speed);
 }
 
 // enable - starts allowing signals to be sent to motors
 void AP_MotorsCoax::enable()
 {
     // enable output channels
-    hal.rcout->enable_ch(AP_MOTORS_MOT_1);
-    hal.rcout->enable_ch(AP_MOTORS_MOT_2);
-    hal.rcout->enable_ch(AP_MOTORS_MOT_3);
-    hal.rcout->enable_ch(AP_MOTORS_MOT_4);
+    rc_enable_ch(AP_MOTORS_MOT_1);
+    rc_enable_ch(AP_MOTORS_MOT_2);
+    rc_enable_ch(AP_MOTORS_MOT_3);
+    rc_enable_ch(AP_MOTORS_MOT_4);
 }
 
 // output_min - sends minimum values out to the motor and trim values to the servos
diff --git a/libraries/AP_Motors/AP_MotorsHeli_Single.cpp b/libraries/AP_Motors/AP_MotorsHeli_Single.cpp
index ab0bfed3c1..27451eb9bd 100644
--- a/libraries/AP_Motors/AP_MotorsHeli_Single.cpp
+++ b/libraries/AP_Motors/AP_MotorsHeli_Single.cpp
@@ -131,19 +131,19 @@ void AP_MotorsHeli_Single::set_update_rate( uint16_t speed_hz )
         1U << AP_MOTORS_MOT_2 |
         1U << AP_MOTORS_MOT_3 |
         1U << AP_MOTORS_MOT_4;
-    hal.rcout->set_freq(mask, _speed_hz);
+    rc_set_freq(mask, _speed_hz);
 }
 
 // enable - starts allowing signals to be sent to motors and servos
 void AP_MotorsHeli_Single::enable()
 {
     // enable output channels
-    hal.rcout->enable_ch(AP_MOTORS_MOT_1);    // swash servo 1
-    hal.rcout->enable_ch(AP_MOTORS_MOT_2);    // swash servo 2
-    hal.rcout->enable_ch(AP_MOTORS_MOT_3);    // swash servo 3
-    hal.rcout->enable_ch(AP_MOTORS_MOT_4);    // yaw
-    hal.rcout->enable_ch(AP_MOTORS_HELI_SINGLE_AUX);                                 // output for gyro gain or direct drive variable pitch tail motor
-    hal.rcout->enable_ch(AP_MOTORS_HELI_SINGLE_RSC);                                 // output for main rotor esc
+    rc_enable_ch(AP_MOTORS_MOT_1);    // swash servo 1
+    rc_enable_ch(AP_MOTORS_MOT_2);    // swash servo 2
+    rc_enable_ch(AP_MOTORS_MOT_3);    // swash servo 3
+    rc_enable_ch(AP_MOTORS_MOT_4);    // yaw
+    rc_enable_ch(AP_MOTORS_HELI_SINGLE_AUX);                                 // output for gyro gain or direct drive variable pitch tail motor
+    rc_enable_ch(AP_MOTORS_HELI_SINGLE_RSC);                                 // output for main rotor esc
 }
 
 // init_outputs - initialise Servo/PWM ranges and endpoints
diff --git a/libraries/AP_Motors/AP_MotorsMatrix.cpp b/libraries/AP_Motors/AP_MotorsMatrix.cpp
index b03cb512ff..dd15bc97dc 100644
--- a/libraries/AP_Motors/AP_MotorsMatrix.cpp
+++ b/libraries/AP_Motors/AP_MotorsMatrix.cpp
@@ -49,7 +49,7 @@ void AP_MotorsMatrix::set_update_rate( uint16_t speed_hz )
 		mask |= 1U << i;
         }
     }
-    hal.rcout->set_freq( mask, _speed_hz );
+    rc_set_freq( mask, _speed_hz );
 }
 
 // set frame orientation (normally + or X)
@@ -78,7 +78,7 @@ void AP_MotorsMatrix::enable()
     // enable output channels
     for( i=0; i<AP_MOTORS_MAX_NUM_MOTORS; i++ ) {
         if( motor_enabled[i] ) {
-            hal.rcout->enable_ch(i);
+            rc_enable_ch(i);
         }
     }
 }
diff --git a/libraries/AP_Motors/AP_MotorsSingle.cpp b/libraries/AP_Motors/AP_MotorsSingle.cpp
index 8705088ba9..a1a21b2f62 100644
--- a/libraries/AP_Motors/AP_MotorsSingle.cpp
+++ b/libraries/AP_Motors/AP_MotorsSingle.cpp
@@ -96,20 +96,20 @@ void AP_MotorsSingle::set_update_rate( uint16_t speed_hz )
         1U << AP_MOTORS_MOT_2 |
         1U << AP_MOTORS_MOT_3 |
         1U << AP_MOTORS_MOT_4 ;
-    hal.rcout->set_freq(mask, _servo_speed);
+    rc_set_freq(mask, _servo_speed);
     uint32_t mask2 = 1U << AP_MOTORS_MOT_7;
-    hal.rcout->set_freq(mask2, _speed_hz);
+    rc_set_freq(mask2, _speed_hz);
 }
 
 // enable - starts allowing signals to be sent to motors
 void AP_MotorsSingle::enable()
 {
     // enable output channels
-    hal.rcout->enable_ch(AP_MOTORS_MOT_1);
-    hal.rcout->enable_ch(AP_MOTORS_MOT_2);
-    hal.rcout->enable_ch(AP_MOTORS_MOT_3);
-    hal.rcout->enable_ch(AP_MOTORS_MOT_4);
-    hal.rcout->enable_ch(AP_MOTORS_MOT_7);
+    rc_enable_ch(AP_MOTORS_MOT_1);
+    rc_enable_ch(AP_MOTORS_MOT_2);
+    rc_enable_ch(AP_MOTORS_MOT_3);
+    rc_enable_ch(AP_MOTORS_MOT_4);
+    rc_enable_ch(AP_MOTORS_MOT_7);
 }
 
 // output_min - sends minimum values out to the motor and trim values to the servos
diff --git a/libraries/AP_Motors/AP_MotorsTri.cpp b/libraries/AP_Motors/AP_MotorsTri.cpp
index 8edec89246..ef169a5d46 100644
--- a/libraries/AP_Motors/AP_MotorsTri.cpp
+++ b/libraries/AP_Motors/AP_MotorsTri.cpp
@@ -97,17 +97,17 @@ void AP_MotorsTri::set_update_rate( uint16_t speed_hz )
 	    1U << AP_MOTORS_MOT_1 |
 	    1U << AP_MOTORS_MOT_2 |
 	    1U << AP_MOTORS_MOT_4;
-    hal.rcout->set_freq(mask, _speed_hz);
+    rc_set_freq(mask, _speed_hz);
 }
 
 // enable - starts allowing signals to be sent to motors
 void AP_MotorsTri::enable()
 {
     // enable output channels
-    hal.rcout->enable_ch(AP_MOTORS_MOT_1);
-    hal.rcout->enable_ch(AP_MOTORS_MOT_2);
-    hal.rcout->enable_ch(AP_MOTORS_MOT_4);
-    hal.rcout->enable_ch(AP_MOTORS_CH_TRI_YAW);
+    rc_enable_ch(AP_MOTORS_MOT_1);
+    rc_enable_ch(AP_MOTORS_MOT_2);
+    rc_enable_ch(AP_MOTORS_MOT_4);
+    rc_enable_ch(AP_MOTORS_CH_TRI_YAW);
 }
 
 // output_min - sends minimum values out to the motors
diff --git a/libraries/AP_Motors/AP_Motors_Class.cpp b/libraries/AP_Motors/AP_Motors_Class.cpp
index d2fbd87ac3..e65e186ef5 100644
--- a/libraries/AP_Motors/AP_Motors_Class.cpp
+++ b/libraries/AP_Motors/AP_Motors_Class.cpp
@@ -76,3 +76,32 @@ void AP_Motors::rc_write(uint8_t chan, uint16_t pwm)
     }
     hal.rcout->write(chan, pwm);
 }
+
+/*
+  set frequency of a set of channels
+ */
+void AP_Motors::rc_set_freq(uint32_t mask, uint16_t freq_hz)
+{
+    uint32_t mask2 = 0;
+    for (uint8_t i=0; i<32; i++) {
+        uint32_t bit = 1UL<<i;
+        if (mask & bit) {
+            if (_motor_map_mask & bit) {
+                // we have a mapped motor number for this channel
+                mask2 |= (1UL << _motor_map[i]);
+            } else {
+                mask2 |= bit;
+            }
+        }
+    }
+    hal.rcout->set_freq(mask2, freq_hz);
+}
+
+void AP_Motors::rc_enable_ch(uint8_t chan)
+{
+    if (_motor_map_mask & (1U<<chan)) {
+        // we have a mapped motor number for this channel
+        chan = _motor_map[chan];
+    }
+    hal.rcout->enable_ch(chan);
+}
diff --git a/libraries/AP_Motors/AP_Motors_Class.h b/libraries/AP_Motors/AP_Motors_Class.h
index ad1094c0ac..fff392a597 100644
--- a/libraries/AP_Motors/AP_Motors_Class.h
+++ b/libraries/AP_Motors/AP_Motors_Class.h
@@ -130,6 +130,8 @@ protected:
     virtual void        output_armed_zero_throttle() { output_min(); }
     virtual void        output_disarmed()=0;
     virtual void        rc_write(uint8_t chan, uint16_t pwm);
+    virtual void        rc_set_freq(uint32_t mask, uint16_t freq_hz);
+    virtual void        rc_enable_ch(uint8_t chan);
     
     // update the throttle input filter
     virtual void        update_throttle_filter() = 0;