diff --git a/src/board_gruvin9x.cpp b/src/board_gruvin9x.cpp
index fbf7413c8..3fb2512c6 100644
--- a/src/board_gruvin9x.cpp
+++ b/src/board_gruvin9x.cpp
@@ -296,5 +296,3 @@ void readKeysAndTrims()
     ++enuk;
   }
 }
-
-uint16_t nextMixerTime = 0;
diff --git a/src/board_gruvin9x.h b/src/board_gruvin9x.h
index aabba787c..4f9048169 100644
--- a/src/board_gruvin9x.h
+++ b/src/board_gruvin9x.h
@@ -34,14 +34,11 @@
 #ifndef board_gruvin9x_h
 #define board_gruvin9x_h
 
-extern uint16_t nextMixerTime;
-
 #define TIMER_16KHZ_VECT TIMER2_OVF_vect
 #define COUNTER_16KHZ TCNT2
 #define TIMER_10MS_VECT  TIMER2_COMPA_vect
 #define PAUSE_10MS_INTERRUPT() TIMSK2 &= ~(1<<OCIE2A)
 #define RESUME_10MS_INTERRUPT() TIMSK2 |= (1<<OCIE2A)
-#define SCHEDULE_MIXER(delay) nextMixerTime = getTmr16KHz() + (delay)
 #define PAUSE_PULSES_INTERRUPT() TIMSK1 &= ~(1<<OCIE1A)
 #define RESUME_PULSES_INTERRUPT() TIMSK1 |= (1<<OCIE1A)
 #define PAUSE_PPMIN_INTERRUPT() TIMSK3 &= ~(1<<ICIE3)
diff --git a/src/board_stock.cpp b/src/board_stock.cpp
index b614d0b07..bd9e42c03 100644
--- a/src/board_stock.cpp
+++ b/src/board_stock.cpp
@@ -199,6 +199,3 @@ bool checkSlaveMode()
   }
   return lastSlaveMode;
 }
-
-uint16_t nextMixerTime = 0;
-
diff --git a/src/board_stock.h b/src/board_stock.h
index 7c85f7544..2ca91af6f 100644
--- a/src/board_stock.h
+++ b/src/board_stock.h
@@ -34,8 +34,6 @@
 #ifndef board_stock_h
 #define board_stock_h
 
-extern uint16_t nextMixerTime;
-
 #define TIMER_16KHZ_VECT TIMER0_OVF_vect
 #define COUNTER_16KHZ TCNT0
 
@@ -46,8 +44,6 @@ extern uint16_t nextMixerTime;
 #define PAUSE_PULSES_INTERRUPT() TIMSK &= ~(1<<OCIE1A);
 #define RESUME_PULSES_INTERRUPT() TIMSK |= (1<<OCIE1A)
 
-#define SCHEDULE_MIXER(delay) nextMixerTime = getTmr16KHz() + (delay)
-
 #define PAUSE_PPMIN_INTERRUPT() ETIMSK &= ~(1<<TICIE3)
 #define RESUME_PPMIN_INTERRUPT() ETIMSK |= (1<<TICIE3)
 
diff --git a/src/gruvin9x/diskio.cpp b/src/gruvin9x/diskio.cpp
index 39edc0a5b..91125bf55 100644
--- a/src/gruvin9x/diskio.cpp
+++ b/src/gruvin9x/diskio.cpp
@@ -104,11 +104,13 @@ BYTE CardType;			/* Card type flags */
 #else
 inline void checkMixer()
 {
+  // TODO duplicated code ...
   uint16_t t0 = getTmr16KHz();
-  int16_t delta = t0 - nextMixerTime;
-  if (delta < 0) return;
+  int16_t delta = (nextMixerEndTime - lastMixerDuration) - t0;
+  if (delta > 0 && delta < MAX_MIXER_DELTA) return;
+
+  nextMixerEndTime = t0 + MAX_MIXER_DELTA;
 
-  nextMixerTime = t0 + 20*16;
   doMixerCalculations();
 
   t0 = getTmr16KHz() - t0;
diff --git a/src/open9x.cpp b/src/open9x.cpp
index 62695c4e6..01aaccf9c 100644
--- a/src/open9x.cpp
+++ b/src/open9x.cpp
@@ -2822,10 +2822,11 @@ void perMain()
   doMixerCalculations();
 #elif !defined(PCBSKY9X)
   uint16_t t0 = getTmr16KHz();
-  int16_t delta = t0 - nextMixerTime;
-  if (delta < 0) return;
+  int16_t delta = (nextMixerEndTime - lastMixerDuration) - t0;
+  if (delta > 0 && delta < MAX_MIXER_DELTA) return;
+
+  nextMixerEndTime = t0 + MAX_MIXER_DELTA;
 
-  nextMixerTime = t0 + 20*16;
   doMixerCalculations();
 
   t0 = getTmr16KHz() - t0;
diff --git a/src/pulses_avr.cpp b/src/pulses_avr.cpp
index 9e957879e..2931c1ae8 100644
--- a/src/pulses_avr.cpp
+++ b/src/pulses_avr.cpp
@@ -33,6 +33,9 @@
 
 #include "open9x.h"
 
+uint16_t nextMixerEndTime = 0;
+#define SCHEDULE_MIXER_END(delay) nextMixerEndTime = getTmr16KHz() + (delay) - 2*16/*2ms*/
+
 #if defined(DSM2)
 // DSM2 control bits
 #define DSM2_CHANS     6
@@ -883,7 +886,7 @@ void setupPulses()
 #ifdef PXX
     case PROTO_PXX:
       // schedule next Mixer calculations
-      SCHEDULE_MIXER(20*16-lastMixerDuration-2*16/*1ms*/);
+      SCHEDULE_MIXER_END(20*16);
       sei();
       setupPulsesPXX();
       break;
@@ -892,7 +895,7 @@ void setupPulses()
 #ifdef DSM2
     case PROTO_DSM2:
       // schedule next Mixer calculations
-      SCHEDULE_MIXER(22*16-lastMixerDuration-2*16/*1ms*/);
+      SCHEDULE_MIXER_END(22*16);
       sei();
       setupPulsesDsm2(); // Different versions for DSM2=SERIAL vs. DSM2=PPM
 #if defined(PCBGRUVIN9X) && defined(DSM2_PPM)
@@ -916,7 +919,7 @@ void setupPulses()
       g_ppmPulsePolarity = g_model.pulsePol;
 #endif
       // schedule next Mixer calculations
-      SCHEDULE_MIXER(45*8+g_model.ppmFrameLength*8-lastMixerDuration-2*16/*1ms*/);
+      SCHEDULE_MIXER_END(45*8+g_model.ppmFrameLength*8);
       // no sei here
       setupPulsesPPM(PROTO_PPM);
       // if PPM16, PPM16 pulses are set up automatically within the interrupts
diff --git a/src/pulses_avr.h b/src/pulses_avr.h
index 98d471ce8..589b288c9 100644
--- a/src/pulses_avr.h
+++ b/src/pulses_avr.h
@@ -40,6 +40,10 @@ extern uint8_t s_pulses_paused;
 extern uint8_t *pulses2MHzRPtr;
 extern uint8_t *pulses2MHzWPtr;
 
+extern uint16_t nextMixerEndTime;
+
+#define MAX_MIXER_DELTA (50*16) /* 50ms max as an interval between 2 mixer calculations */
+
 void startPulses();
 inline bool pulsesStarted() { return s_current_protocol != 255; }
 inline void pausePulses() { s_pulses_paused = true; }