diff --git a/companion/src/firmwares/opentx/opentxGruvin9xsimulator.cpp b/companion/src/firmwares/opentx/opentxGruvin9xsimulator.cpp
index 0da2fe515..a7e1f0db1 100644
--- a/companion/src/firmwares/opentx/opentxGruvin9xsimulator.cpp
+++ b/companion/src/firmwares/opentx/opentxGruvin9xsimulator.cpp
@@ -62,6 +62,7 @@ namespace Open9xGruvin9x {
 #include "radio/src/eeprom_rlc.cpp"
 #include "radio/src/opentx.cpp"
 #include "radio/src/switches.cpp"
+#include "radio/src/curves.cpp"
 #include "radio/src/protocols/pulses_avr.cpp"
 #include "radio/src/stamp.cpp"
 #include "radio/src/maths.cpp"
diff --git a/companion/src/firmwares/opentx/opentxM128simulator.cpp b/companion/src/firmwares/opentx/opentxM128simulator.cpp
index 30b5b1352..18a58dd42 100644
--- a/companion/src/firmwares/opentx/opentxM128simulator.cpp
+++ b/companion/src/firmwares/opentx/opentxM128simulator.cpp
@@ -61,6 +61,7 @@ namespace Open9xM128 {
 #include "radio/src/eeprom_rlc.cpp"
 #include "radio/src/opentx.cpp"
 #include "radio/src/switches.cpp"
+#include "radio/src/curves.cpp"
 #include "radio/src/protocols/pulses_avr.cpp"
 #include "radio/src/stamp.cpp"
 #include "radio/src/maths.cpp"
diff --git a/companion/src/firmwares/opentx/opentxSky9xsimulator.cpp b/companion/src/firmwares/opentx/opentxSky9xsimulator.cpp
index c18c7adcc..9befd70e6 100644
--- a/companion/src/firmwares/opentx/opentxSky9xsimulator.cpp
+++ b/companion/src/firmwares/opentx/opentxSky9xsimulator.cpp
@@ -76,6 +76,7 @@ namespace Open9xSky9x {
 #include "radio/src/eeprom_conversions.cpp"
 #include "radio/src/opentx.cpp"
 #include "radio/src/switches.cpp"
+#include "radio/src/curves.cpp"
 #include "radio/src/targets/sky9x/pulses_driver.cpp"
 #include "radio/src/protocols/pulses_arm.cpp"
 #include "radio/src/stamp.cpp"
diff --git a/companion/src/firmwares/opentx/opentxTaranisSimulator.cpp b/companion/src/firmwares/opentx/opentxTaranisSimulator.cpp
index 5c4474b07..87bd1062d 100644
--- a/companion/src/firmwares/opentx/opentxTaranisSimulator.cpp
+++ b/companion/src/firmwares/opentx/opentxTaranisSimulator.cpp
@@ -79,6 +79,7 @@ inline int geteepromsize() {
 #include "radio/src/eeprom_rlc.cpp"
 #include "radio/src/opentx.cpp"
 #include "radio/src/switches.cpp"
+#include "radio/src/curves.cpp"
 #include "radio/src/targets/taranis/pulses_driver.cpp"
 #include "radio/src/targets/taranis/rtc_driver.cpp"
 #include "radio/src/targets/taranis/trainer_driver.cpp"
diff --git a/companion/src/firmwares/opentx/opentxsimulator.cpp b/companion/src/firmwares/opentx/opentxsimulator.cpp
index d20ba68f1..2dab2960c 100644
--- a/companion/src/firmwares/opentx/opentxsimulator.cpp
+++ b/companion/src/firmwares/opentx/opentxsimulator.cpp
@@ -67,6 +67,7 @@ namespace Open9x {
 #include "radio/src/eeprom_rlc.cpp"
 #include "radio/src/opentx.cpp"
 #include "radio/src/switches.cpp"
+#include "radio/src/curves.cpp"
 #include "radio/src/protocols/pulses_avr.cpp"
 #include "radio/src/stamp.cpp"
 #include "radio/src/maths.cpp"
diff --git a/radio/src/Makefile b/radio/src/Makefile
index 945329b88..b0347c3a1 100644
--- a/radio/src/Makefile
+++ b/radio/src/Makefile
@@ -759,7 +759,7 @@ else
   TTS_SRC = $(shell sh -c "if test -f $(STD_TTS_SRC); then echo $(STD_TTS_SRC); else echo translations/tts_en.cpp; fi")
 endif
 
-CPPSRC += opentx.cpp $(PULSESSRC) switches.cpp stamp.cpp gui/menus.cpp gui/menu_model.cpp gui/menu_general.cpp gui/view_main.cpp gui/view_statistics.cpp $(EEPROMSRC) lcd.cpp keys.cpp maths.cpp translations.cpp fonts.cpp $(TTS_SRC)
+CPPSRC += opentx.cpp $(PULSESSRC) switches.cpp curves.cpp stamp.cpp gui/menus.cpp gui/menu_model.cpp gui/menu_general.cpp gui/view_main.cpp gui/view_statistics.cpp $(EEPROMSRC) lcd.cpp keys.cpp maths.cpp translations.cpp fonts.cpp $(TTS_SRC)
 
 # Debugging format.
 #     Native formats for AVR-GCC's -g are dwarf-2 [default] or stabs.
diff --git a/radio/src/curves.cpp b/radio/src/curves.cpp
new file mode 100755
index 000000000..c6eaffccc
--- /dev/null
+++ b/radio/src/curves.cpp
@@ -0,0 +1,432 @@
+/*
+ * Authors (alphabetical order)
+ * - Andre Bernet <bernet.andre@gmail.com>
+ * - Andreas Weitl
+ * - Bertrand Songis <bsongis@gmail.com>
+ * - Bryan J. Rentoul (Gruvin) <gruvin@gmail.com>
+ * - Cameron Weeks <th9xer@gmail.com>
+ * - Erez Raviv
+ * - Gabriel Birkus
+ * - Jean-Pierre Parisy
+ * - Karl Szmutny
+ * - Michael Blandford
+ * - Michal Hlavinka
+ * - Pat Mackenzie
+ * - Philip Moss
+ * - Rob Thomson
+ * - Romolo Manfredini <romolo.manfredini@gmail.com>
+ * - Thomas Husterer
+ *
+ * opentx is based on code named
+ * gruvin9x by Bryan J. Rentoul: http://code.google.com/p/gruvin9x/,
+ * er9x by Erez Raviv: http://code.google.com/p/er9x/,
+ * and the original (and ongoing) project by
+ * Thomas Husterer, th9x: http://code.google.com/p/th9x/
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include "opentx.h"
+
+#if defined(PCBTARANIS)
+int8_t *curveEnd[MAX_CURVES];
+void loadCurves()
+{
+  int8_t * tmp = g_model.points;
+  for (int i=0; i<MAX_CURVES; i++) {
+    switch (g_model.curves[i].type) {
+      case CURVE_TYPE_STANDARD:
+        tmp += 5+g_model.curves[i].points;
+        break;
+      case CURVE_TYPE_CUSTOM:
+        tmp += 8+2*g_model.curves[i].points;
+        break;
+    }
+    curveEnd[i] = tmp;
+  }
+}
+int8_t *curveAddress(uint8_t idx)
+{
+  return idx==0 ? g_model.points : curveEnd[idx-1];
+}
+#else
+int8_t *curveAddress(uint8_t idx)
+{
+  return &g_model.points[idx==0 ? 0 : 5*idx+g_model.curves[idx-1]];
+}
+
+CurveInfo curveInfo(uint8_t idx)
+{
+  CurveInfo result;
+  result.crv = curveAddress(idx);
+  int8_t *next = curveAddress(idx+1);
+  uint8_t size = next - result.crv;
+  if ((size & 1) == 0) {
+    result.points = (size / 2) + 1;
+    result.custom = true;
+  }
+  else {
+    result.points = size;
+    result.custom = false;
+  }
+  return result;
+}
+#endif
+
+#if defined(PCBTARANIS)
+#define CUSTOM_POINT_X(points, count, idx) ((idx)==0 ? -100 : (((idx)==(count)-1) ? 100 : points[(count)+(idx)-1]))
+s32 compute_tangent(CurveInfo *crv, int8_t *points, int i)
+{
+    s32 m=0;
+    uint8_t num_points = crv->points + 5;
+    #define MMULT 1024
+    if (i == 0) {
+      //linear interpolation between 1st 2 points
+      //keep 3 decimal-places for m
+      if (crv->type == CURVE_TYPE_CUSTOM) {
+        int8_t x0 = CUSTOM_POINT_X(points, num_points, 0);
+        int8_t x1 = CUSTOM_POINT_X(points, num_points, 1);
+        if (x1 > x0) m = (MMULT * (points[1] - points[0])) / (x1 - x0);
+      }
+      else {
+        s32 delta = (2 * 100) / (num_points - 1);
+        m = (MMULT * (points[1] - points[0])) / delta;
+      }
+    }
+    else if (i == num_points - 1) {
+      //linear interpolation between last 2 points
+      //keep 3 decimal-places for m
+      if (crv->type == CURVE_TYPE_CUSTOM) {
+        int8_t x0 = CUSTOM_POINT_X(points, num_points, num_points-2);
+        int8_t x1 = CUSTOM_POINT_X(points, num_points, num_points-1);
+        if (x1 > x0) m = (MMULT * (points[num_points-1] - points[num_points-2])) / (x1 - x0);
+      }
+      else {
+        s32 delta = (2 * 100) / (num_points - 1);
+        m = (MMULT * (points[num_points-1] - points[num_points-2])) / delta;
+      }
+    }
+    else {
+        //apply monotone rules from
+        //http://en.wikipedia.org/wiki/Monotone_cubic_interpolation
+        //1) compute slopes of secant lines
+        s32 d0=0, d1=0;
+        if (crv->type == CURVE_TYPE_CUSTOM) {
+          int8_t x0 = CUSTOM_POINT_X(points, num_points, i-1);
+          int8_t x1 = CUSTOM_POINT_X(points, num_points, i);
+          int8_t x2 = CUSTOM_POINT_X(points, num_points, i+1);
+          if (x1 > x0) d0 = (MMULT * (points[i] - points[i-1])) / (x1 - x0);
+          if (x2 > x1) d1 = (MMULT * (points[i+1] - points[i])) / (x2 - x1);
+        }
+        else {
+          s32 delta = (2 * 100) / (num_points - 1);
+          d0 = (MMULT * (points[i] - points[i-1])) / (delta);
+          d1 = (MMULT * (points[i+1] - points[i])) / (delta);
+        }
+        //2) compute initial average tangent
+        m = (d0 + d1) / 2;
+        //3 check for horizontal lines
+        if (d0 == 0 || d1 == 0 || (d0 > 0 && d1 < 0) || (d0 < 0 && d1 > 0)) {
+          m = 0;
+        }
+        else if (MMULT * m / d0 >  3 * MMULT) {
+          m = 3 * d0;
+        }
+        else if (MMULT * m / d1 > 3 * MMULT) {
+          m = 3 * d1;
+        }
+    }
+    return m;
+}
+
+/* The following is a hermite cubic spline.
+   The basis functions can be found here:
+   http://en.wikipedia.org/wiki/Cubic_Hermite_spline
+   The tangents are computed via the 'cubic monotone' rules (allowing for local-maxima)
+*/
+int16_t hermite_spline(int16_t x, uint8_t idx)
+{
+  CurveInfo &crv = g_model.curves[idx];
+  int8_t *points = curveAddress(idx);
+  uint8_t count = crv.points+5;
+  bool custom = (crv.type == CURVE_TYPE_CUSTOM);
+
+  if (x < -RESX)
+    x = -RESX;
+  else if (x > RESX)
+    x = RESX;
+
+  for (int i=0; i<count-1; i++) {
+    s32 p0x, p3x;
+    if (custom) {
+      p0x = (i>0 ? calc100toRESX(points[count+i-1]) : -RESX);
+      p3x = (i<count-2 ? calc100toRESX(points[count+i]) : RESX);
+    }
+    else {
+      p0x = -RESX + (i*2*RESX)/(count-1);
+      p3x = -RESX + ((i+1)*2*RESX)/(count-1);
+    }
+
+    if (x >= p0x && x <= p3x) {
+      s32 p0y = calc100toRESX(points[i]);
+      s32 p3y = calc100toRESX(points[i+1]);
+      s32 m0 = compute_tangent(&crv, points, i);
+      s32 m3 = compute_tangent(&crv, points, i+1);
+      s32 y;
+      s32 h = p3x - p0x;
+      s32 t = (h > 0 ? (MMULT * (x - p0x)) / h : 0);
+      s32 t2 = t * t / MMULT;
+      s32 t3 = t2 * t / MMULT;
+      s32 h00 = 2*t3 - 3*t2 + MMULT;
+      s32 h10 = t3 - 2*t2 + t;
+      s32 h01 = -2*t3 + 3*t2;
+      s32 h11 = t3 - t2;
+      y = p0y * h00 + h * (m0 * h10 / MMULT) + p3y * h01 + h * (m3 * h11 / MMULT);
+      y /= MMULT;
+      return y;
+    }
+  }
+  return 0;
+}
+#endif
+
+int intpol(int x, uint8_t idx) // -100, -75, -50, -25, 0 ,25 ,50, 75, 100
+{
+#if defined(PCBTARANIS)
+  CurveInfo &crv = g_model.curves[idx];
+  int8_t *points = curveAddress(idx);
+  uint8_t count = crv.points+5;
+  bool custom = (crv.type == CURVE_TYPE_CUSTOM);
+#else
+  CurveInfo crv = curveInfo(idx);
+  int8_t *points = crv.crv;
+  uint8_t count = crv.points;
+  bool custom = crv.custom;
+#endif
+  int16_t erg = 0;
+
+  x += RESXu;
+
+  if (x <= 0) {
+    erg = (int16_t)points[0] * (RESX/4);
+  }
+  else if (x >= (RESX*2)) {
+    erg = (int16_t)points[count-1] * (RESX/4);
+  }
+  else {
+    uint16_t a=0, b=0;
+    uint8_t i;
+    if (custom) {
+      for (i=0; i<count-1; i++) {
+        a = b;
+        b = (i==count-2 ? 2*RESX : RESX + calc100toRESX(points[count+i]));
+        if ((uint16_t)x<=b) break;
+      }
+    }
+    else {
+      uint16_t d = (RESX * 2) / (count-1);
+      i = (uint16_t)x / d;
+      a = i * d;
+      b = a + d;
+    }
+    erg = (int16_t)points[i]*(RESX/4) + ((int32_t)(x-a) * (points[i+1]-points[i]) * (RESX/4)) / ((b-a));
+  }
+
+  return erg / 25; // 100*D5/RESX;
+}
+
+#if defined(CURVES)
+#if defined(PCBTARANIS)
+int applyCurve(int x, CurveRef & curve)
+{
+  switch (curve.type) {
+    case CURVE_REF_DIFF:
+    {
+      int curveParam = calc100to256(GET_GVAR(curve.value, -100, 100, s_perout_flight_mode));
+      if (curveParam > 0 && x < 0)
+        x = (x * (256 - curveParam)) >> 8;
+      else if (curveParam < 0 && x > 0)
+        x = (x * (256 + curveParam)) >> 8;
+      return x;
+    }
+
+    case CURVE_REF_EXPO:
+      return expo(x, GET_GVAR(curve.value, -100, 100, s_perout_flight_mode));
+
+    case CURVE_REF_FUNC:
+      switch (curve.value) {
+        case CURVE_X_GT0:
+          if (x < 0) x = 0; //x|x>0
+          return x;
+        case CURVE_X_LT0:
+          if (x > 0) x = 0; //x|x<0
+          return x;
+        case CURVE_ABS_X: // x|abs(x)
+          return abs(x);
+        case CURVE_F_GT0: //f|f>0
+          return x > 0 ? RESX : 0;
+        case CURVE_F_LT0: //f|f<0
+          return x < 0 ? -RESX : 0;
+        case CURVE_ABS_F: //f|abs(f)
+          return x > 0 ? RESX : -RESX;
+      }
+      break;
+
+    case CURVE_REF_CUSTOM:
+    {
+      int curveParam = curve.value;
+      if (curveParam < 0) {
+        x = -x;
+        curveParam = -curveParam;
+      }
+      if (curveParam > 0 && curveParam <= MAX_CURVES) {
+        return applyCustomCurve(x, curveParam - 1);
+      }
+      break;
+    }
+  }
+
+  return x;
+}
+
+int applyCustomCurve(int x, uint8_t idx)
+{
+  CurveInfo &crv = g_model.curves[idx];
+  if (crv.smooth)
+    return hermite_spline(x, idx);
+  else
+    return intpol(x, idx);
+}
+
+#else
+int applyCurve(int x, int8_t idx)
+{
+  /* already tried to have only one return at the end */
+  switch(idx) {
+    case CURVE_NONE:
+      return x;
+    case CURVE_X_GT0:
+      if (x < 0) x = 0; //x|x>0
+      return x;
+    case CURVE_X_LT0:
+      if (x > 0) x = 0; //x|x<0
+      return x;
+    case CURVE_ABS_X: // x|abs(x)
+      return abs(x);
+    case CURVE_F_GT0: //f|f>0
+      return x > 0 ? RESX : 0;
+    case CURVE_F_LT0: //f|f<0
+      return x < 0 ? -RESX : 0;
+    case CURVE_ABS_F: //f|abs(f)
+      return x > 0 ? RESX : -RESX;
+  }
+  if (idx < 0) {
+    x = -x;
+    idx = -idx + CURVE_BASE - 1;
+  }
+  return applyCustomCurve(x, idx - CURVE_BASE);
+}
+#endif
+#endif
+
+// #define EXTENDED_EXPO
+// increases range of expo curve but costs about 82 bytes flash
+
+// expo-funktion:
+// ---------------
+// kmplot
+// f(x,k)=exp(ln(x)*k/10) ;P[0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]
+// f(x,k)=x*x*x*k/10 + x*(1-k/10) ;P[0,1,2,3,4,5,6,7,8,9,10]
+// f(x,k)=x*x*k/10 + x*(1-k/10) ;P[0,1,2,3,4,5,6,7,8,9,10]
+// f(x,k)=1+(x-1)*(x-1)*(x-1)*k/10 + (x-1)*(1-k/10) ;P[0,1,2,3,4,5,6,7,8,9,10]
+// don't know what this above should be, just confusing in my opinion,
+
+// here is the real explanation
+// actually the real formula is
+/*
+ f(x) = exp( ln(x) * 10^k)
+ if it is 10^k or e^k or 2^k etc. just defines the max distortion of the expo curve; I think 10 is useful
+ this gives values from 0 to 1 for x and output; k must be between -1 and +1
+ we do not like to calculate with floating point. Therefore we rescale for x from 0 to 1024 and for k from -100 to +100
+ f(x) = 1024 * ( e^( ln(x/1024) * 10^(k/100) ) )
+ This would be really hard to be calculated by such a microcontroller
+ Therefore Thomas Husterer compared a few usual function something like x^3, x^4*something, which look similar
+ Actually the formula
+ f(x) = k*x^3+x*(1-k)
+ gives a similar form and should have even advantages compared to a original exp curve.
+ This function again expect x from 0 to 1 and k only from 0 to 1
+ Therefore rescaling is needed like before:
+ f(x) = 1024* ((k/100)*(x/1024)^3 + (x/1024)*(100-k)/100)
+ some mathematical tricks
+ f(x) = (k*x*x*x/(1024*1024) + x*(100-k)) / 100
+ for better rounding results we add the 50
+ f(x) = (k*x*x*x/(1024*1024) + x*(100-k) + 50) / 100
+
+ because we now understand the formula, we can optimize it further
+ --> calc100to256(k) --> eliminates /100 by replacing with /256 which is just a simple shift right 8
+ k is now between 0 and 256
+ f(x) = (k*x*x*x/(1024*1024) + x*(256-k) + 128) / 256
+ */
+
+// input parameters;
+//  x 0 to 1024;
+//  k 0 to 100;
+// output between 0 and 1024
+unsigned int expou(unsigned int x, unsigned int k)
+{
+#if defined(EXTENDED_EXPO)
+  bool extended;
+  if (k>80) {
+    extended=true;
+  }
+  else {
+    k += (k>>2);  // use bigger values before extend, because the effect is anyway very very low
+    extended=false;
+  }
+#endif
+
+  k = calc100to256(k);
+
+  uint32_t value = (uint32_t) x*x;
+  value *= (uint32_t)k;
+  value >>= 8;
+  value *= (uint32_t)x;
+
+#if defined(EXTENDED_EXPO)
+  if (extended) {  // for higher values do more multiplications to get a stronger expo curve
+    value >>= 16;
+    value *= (uint32_t)x;
+    value >>= 4;
+    value *= (uint32_t)x;
+  }
+#endif
+
+  value >>= 12;
+  value += (uint32_t)(256-k)*x+128;
+
+  return value>>8;
+}
+
+int expo(int x, int k)
+{
+  if (k == 0) return x;
+  int y;
+  bool neg = (x < 0);
+
+  if (neg) x = -x;
+  if (k<0) {
+    y = RESXu-expou(RESXu-x, -k);
+  }
+  else {
+    y = expou(x, k);
+  }
+  return neg? -y : y;
+}
diff --git a/radio/src/opentx.cpp b/radio/src/opentx.cpp
index 04b7c78db..8afc6e5f1 100644
--- a/radio/src/opentx.cpp
+++ b/radio/src/opentx.cpp
@@ -407,51 +407,6 @@ LimitData *limitAddress(uint8_t idx)
   return &g_model.limitData[idx];
 }
 
-#if defined(PCBTARANIS)
-int8_t *curveEnd[MAX_CURVES];
-void loadCurves()
-{
-  int8_t * tmp = g_model.points;
-  for (int i=0; i<MAX_CURVES; i++) {
-    switch (g_model.curves[i].type) {
-      case CURVE_TYPE_STANDARD:
-        tmp += 5+g_model.curves[i].points;
-        break;
-      case CURVE_TYPE_CUSTOM:
-        tmp += 8+2*g_model.curves[i].points;
-        break;
-    }
-    curveEnd[i] = tmp;
-  }
-}
-int8_t *curveAddress(uint8_t idx)
-{
-  return idx==0 ? g_model.points : curveEnd[idx-1];
-}
-#else
-int8_t *curveAddress(uint8_t idx)
-{
-  return &g_model.points[idx==0 ? 0 : 5*idx+g_model.curves[idx-1]];
-}
-
-CurveInfo curveInfo(uint8_t idx)
-{
-  CurveInfo result;
-  result.crv = curveAddress(idx);
-  int8_t *next = curveAddress(idx+1);
-  uint8_t size = next - result.crv;
-  if ((size & 1) == 0) {
-    result.points = (size / 2) + 1;
-    result.custom = true;
-  }
-  else {
-    result.points = size;
-    result.custom = false;
-  }
-  return result;
-}
-#endif
-
 LogicalSwitchData *cswAddress(uint8_t idx)
 {
   return &g_model.customSw[idx];
@@ -601,357 +556,6 @@ void modelDefault(uint8_t id)
 #endif
 }
 
-#if defined(PCBTARANIS)
-#define CUSTOM_POINT_X(points, count, idx) ((idx)==0 ? -100 : (((idx)==(count)-1) ? 100 : points[(count)+(idx)-1]))
-s32 compute_tangent(CurveInfo *crv, int8_t *points, int i)
-{
-    s32 m=0;
-    uint8_t num_points = crv->points + 5;
-    #define MMULT 1024
-    if (i == 0) {
-      //linear interpolation between 1st 2 points
-      //keep 3 decimal-places for m
-      if (crv->type == CURVE_TYPE_CUSTOM) {
-        int8_t x0 = CUSTOM_POINT_X(points, num_points, 0);
-        int8_t x1 = CUSTOM_POINT_X(points, num_points, 1);
-        if (x1 > x0) m = (MMULT * (points[1] - points[0])) / (x1 - x0);
-      }
-      else {
-        s32 delta = (2 * 100) / (num_points - 1);
-        m = (MMULT * (points[1] - points[0])) / delta;
-      }
-    }
-    else if (i == num_points - 1) {
-      //linear interpolation between last 2 points
-      //keep 3 decimal-places for m
-      if (crv->type == CURVE_TYPE_CUSTOM) {
-        int8_t x0 = CUSTOM_POINT_X(points, num_points, num_points-2);
-        int8_t x1 = CUSTOM_POINT_X(points, num_points, num_points-1);
-        if (x1 > x0) m = (MMULT * (points[num_points-1] - points[num_points-2])) / (x1 - x0);
-      }
-      else {
-        s32 delta = (2 * 100) / (num_points - 1);
-        m = (MMULT * (points[num_points-1] - points[num_points-2])) / delta;
-      }
-    }
-    else {
-        //apply monotone rules from
-        //http://en.wikipedia.org/wiki/Monotone_cubic_interpolation
-        //1) compute slopes of secant lines
-        s32 d0=0, d1=0;
-        if (crv->type == CURVE_TYPE_CUSTOM) {
-          int8_t x0 = CUSTOM_POINT_X(points, num_points, i-1);
-          int8_t x1 = CUSTOM_POINT_X(points, num_points, i);
-          int8_t x2 = CUSTOM_POINT_X(points, num_points, i+1);
-          if (x1 > x0) d0 = (MMULT * (points[i] - points[i-1])) / (x1 - x0);
-          if (x2 > x1) d1 = (MMULT * (points[i+1] - points[i])) / (x2 - x1);
-        }
-        else {
-          s32 delta = (2 * 100) / (num_points - 1);
-          d0 = (MMULT * (points[i] - points[i-1])) / (delta);
-          d1 = (MMULT * (points[i+1] - points[i])) / (delta);
-        }
-        //2) compute initial average tangent
-        m = (d0 + d1) / 2;
-        //3 check for horizontal lines
-        if (d0 == 0 || d1 == 0 || (d0 > 0 && d1 < 0) || (d0 < 0 && d1 > 0)) {
-          m = 0;
-        }
-        else if (MMULT * m / d0 >  3 * MMULT) {
-          m = 3 * d0;
-        }
-        else if (MMULT * m / d1 > 3 * MMULT) {
-          m = 3 * d1;
-        }
-    }
-    return m;
-}
-
-/* The following is a hermite cubic spline.
-   The basis functions can be found here:
-   http://en.wikipedia.org/wiki/Cubic_Hermite_spline
-   The tangents are computed via the 'cubic monotone' rules (allowing for local-maxima)
-*/
-int16_t hermite_spline(int16_t x, uint8_t idx)
-{
-  CurveInfo &crv = g_model.curves[idx];
-  int8_t *points = curveAddress(idx);
-  uint8_t count = crv.points+5;
-  bool custom = (crv.type == CURVE_TYPE_CUSTOM);
-
-  if (x < -RESX)
-    x = -RESX;
-  else if (x > RESX)
-    x = RESX;
-
-  for (int i=0; i<count-1; i++) {
-    s32 p0x, p3x;
-    if (custom) {
-      p0x = (i>0 ? calc100toRESX(points[count+i-1]) : -RESX);
-      p3x = (i<count-2 ? calc100toRESX(points[count+i]) : RESX);
-    }
-    else {
-      p0x = -RESX + (i*2*RESX)/(count-1);
-      p3x = -RESX + ((i+1)*2*RESX)/(count-1);
-    }
-
-    if (x >= p0x && x <= p3x) {
-      s32 p0y = calc100toRESX(points[i]);
-      s32 p3y = calc100toRESX(points[i+1]);
-      s32 m0 = compute_tangent(&crv, points, i);
-      s32 m3 = compute_tangent(&crv, points, i+1);
-      s32 y;
-      s32 h = p3x - p0x;
-      s32 t = (h > 0 ? (MMULT * (x - p0x)) / h : 0);
-      s32 t2 = t * t / MMULT;
-      s32 t3 = t2 * t / MMULT;
-      s32 h00 = 2*t3 - 3*t2 + MMULT;
-      s32 h10 = t3 - 2*t2 + t;
-      s32 h01 = -2*t3 + 3*t2;
-      s32 h11 = t3 - t2;
-      y = p0y * h00 + h * (m0 * h10 / MMULT) + p3y * h01 + h * (m3 * h11 / MMULT);
-      y /= MMULT;
-      return y;
-    }
-  }
-  return 0;
-}
-#endif
-
-int intpol(int x, uint8_t idx) // -100, -75, -50, -25, 0 ,25 ,50, 75, 100
-{
-#if defined(PCBTARANIS)
-  CurveInfo &crv = g_model.curves[idx];
-  int8_t *points = curveAddress(idx);
-  uint8_t count = crv.points+5;
-  bool custom = (crv.type == CURVE_TYPE_CUSTOM);
-#else
-  CurveInfo crv = curveInfo(idx);
-  int8_t *points = crv.crv;
-  uint8_t count = crv.points;
-  bool custom = crv.custom;
-#endif
-  int16_t erg = 0;
-
-  x += RESXu;
-
-  if (x <= 0) {
-    erg = (int16_t)points[0] * (RESX/4);
-  }
-  else if (x >= (RESX*2)) {
-    erg = (int16_t)points[count-1] * (RESX/4);
-  }
-  else {
-    uint16_t a=0, b=0;
-    uint8_t i;
-    if (custom) {
-      for (i=0; i<count-1; i++) {
-        a = b;
-        b = (i==count-2 ? 2*RESX : RESX + calc100toRESX(points[count+i]));
-        if ((uint16_t)x<=b) break;
-      }
-    }
-    else {
-      uint16_t d = (RESX * 2) / (count-1);
-      i = (uint16_t)x / d;
-      a = i * d;
-      b = a + d;
-    }
-    erg = (int16_t)points[i]*(RESX/4) + ((int32_t)(x-a) * (points[i+1]-points[i]) * (RESX/4)) / ((b-a));
-  }
-
-  return erg / 25; // 100*D5/RESX;
-}
-
-#if defined(CURVES)
-#if defined(PCBTARANIS)
-int applyCurve(int x, CurveRef & curve)
-{
-  switch (curve.type) {
-    case CURVE_REF_DIFF:
-    {
-      int curveParam = calc100to256(GET_GVAR(curve.value, -100, 100, s_perout_flight_mode));
-      if (curveParam > 0 && x < 0)
-        x = (x * (256 - curveParam)) >> 8;
-      else if (curveParam < 0 && x > 0)
-        x = (x * (256 + curveParam)) >> 8;
-      return x;
-    }
-
-    case CURVE_REF_EXPO:
-      return expo(x, GET_GVAR(curve.value, -100, 100, s_perout_flight_mode));
-
-    case CURVE_REF_FUNC:
-      switch (curve.value) {
-        case CURVE_X_GT0:
-          if (x < 0) x = 0; //x|x>0
-          return x;
-        case CURVE_X_LT0:
-          if (x > 0) x = 0; //x|x<0
-          return x;
-        case CURVE_ABS_X: // x|abs(x)
-          return abs(x);
-        case CURVE_F_GT0: //f|f>0
-          return x > 0 ? RESX : 0;
-        case CURVE_F_LT0: //f|f<0
-          return x < 0 ? -RESX : 0;
-        case CURVE_ABS_F: //f|abs(f)
-          return x > 0 ? RESX : -RESX;
-      }
-      break;
-
-    case CURVE_REF_CUSTOM:
-    {
-      int curveParam = curve.value;
-      if (curveParam < 0) {
-        x = -x;
-        curveParam = -curveParam;
-      }
-      if (curveParam > 0 && curveParam <= MAX_CURVES) {
-        return applyCustomCurve(x, curveParam - 1);
-      }
-      break;
-    }
-  }
-
-  return x;
-}
-
-int applyCustomCurve(int x, uint8_t idx)
-{
-  CurveInfo &crv = g_model.curves[idx];
-  if (crv.smooth)
-    return hermite_spline(x, idx);
-  else
-    return intpol(x, idx);
-}
-
-#else
-int applyCurve(int x, int8_t idx)
-{
-  /* already tried to have only one return at the end */
-  switch(idx) {
-    case CURVE_NONE:
-      return x;
-    case CURVE_X_GT0:
-      if (x < 0) x = 0; //x|x>0
-      return x;
-    case CURVE_X_LT0:
-      if (x > 0) x = 0; //x|x<0
-      return x;
-    case CURVE_ABS_X: // x|abs(x)
-      return abs(x);
-    case CURVE_F_GT0: //f|f>0
-      return x > 0 ? RESX : 0;
-    case CURVE_F_LT0: //f|f<0
-      return x < 0 ? -RESX : 0;
-    case CURVE_ABS_F: //f|abs(f)
-      return x > 0 ? RESX : -RESX;
-  }
-  if (idx < 0) {
-    x = -x;
-    idx = -idx + CURVE_BASE - 1;
-  }
-  return applyCustomCurve(x, idx - CURVE_BASE);
-}
-#endif
-#else
-#define applyCurve(x, idx) (x)
-#endif
-
-// #define EXTENDED_EXPO
-// increases range of expo curve but costs about 82 bytes flash
-
-// expo-funktion:
-// ---------------
-// kmplot
-// f(x,k)=exp(ln(x)*k/10) ;P[0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]
-// f(x,k)=x*x*x*k/10 + x*(1-k/10) ;P[0,1,2,3,4,5,6,7,8,9,10]
-// f(x,k)=x*x*k/10 + x*(1-k/10) ;P[0,1,2,3,4,5,6,7,8,9,10]
-// f(x,k)=1+(x-1)*(x-1)*(x-1)*k/10 + (x-1)*(1-k/10) ;P[0,1,2,3,4,5,6,7,8,9,10]
-// don't know what this above should be, just confusing in my opinion,
-
-// here is the real explanation
-// actually the real formula is  
-/*
- f(x) = exp( ln(x) * 10^k)  
- if it is 10^k or e^k or 2^k etc. just defines the max distortion of the expo curve; I think 10 is useful
- this gives values from 0 to 1 for x and output; k must be between -1 and +1
- we do not like to calculate with floating point. Therefore we rescale for x from 0 to 1024 and for k from -100 to +100
- f(x) = 1024 * ( e^( ln(x/1024) * 10^(k/100) ) )
- This would be really hard to be calculated by such a microcontroller
- Therefore Thomas Husterer compared a few usual function something like x^3, x^4*something, which look similar
- Actually the formula 
- f(x) = k*x^3+x*(1-k) 
- gives a similar form and should have even advantages compared to a original exp curve.
- This function again expect x from 0 to 1 and k only from 0 to 1
- Therefore rescaling is needed like before:
- f(x) = 1024* ((k/100)*(x/1024)^3 + (x/1024)*(100-k)/100)
- some mathematical tricks 
- f(x) = (k*x*x*x/(1024*1024) + x*(100-k)) / 100
- for better rounding results we add the 50
- f(x) = (k*x*x*x/(1024*1024) + x*(100-k) + 50) / 100
- 
- because we now understand the formula, we can optimize it further
- --> calc100to256(k) --> eliminates /100 by replacing with /256 which is just a simple shift right 8
- k is now between 0 and 256
- f(x) = (k*x*x*x/(1024*1024) + x*(256-k) + 128) / 256
- */
- 
-// input parameters; 
-//  x 0 to 1024;
-//  k 0 to 100;
-// output between 0 and 1024
-unsigned int expou(unsigned int x, unsigned int k)
-{
-#if defined(EXTENDED_EXPO)
-  bool extended;
-  if (k>80) {
-    extended=true;
-  }
-  else {
-    k += (k>>2);  // use bigger values before extend, because the effect is anyway very very low
-    extended=false;
-  }
-#endif  
-
-  k = calc100to256(k);
-  
-  uint32_t value = (uint32_t) x*x;
-  value *= (uint32_t)k;
-  value >>= 8;
-  value *= (uint32_t)x;
-
-#if defined(EXTENDED_EXPO)
-  if (extended) {  // for higher values do more multiplications to get a stronger expo curve
-    value >>= 16;
-    value *= (uint32_t)x;
-    value >>= 4;
-    value *= (uint32_t)x;
-  }
-#endif
-  
-  value >>= 12;
-  value += (uint32_t)(256-k)*x+128;
-
-  return value>>8;
-}
-
-int expo(int x, int k)
-{
-  if (k == 0) return x;
-  int y;
-  bool neg = (x < 0);
-
-  if (neg) x = -x;
-  if (k<0) {
-    y = RESXu-expou(RESXu-x, -k);
-  }
-  else {
-    y = expou(x, k);
-  }
-  return neg? -y : y;
-}
 
 #if defined(HELI)
   int16_t cyc_anas[3] = {0};
@@ -5155,4 +4759,3 @@ int main(void)
 #endif
 }
 #endif // !SIMU
-
diff --git a/radio/src/opentx.h b/radio/src/opentx.h
index e59ab631f..1431448fa 100644
--- a/radio/src/opentx.h
+++ b/radio/src/opentx.h
@@ -1040,7 +1040,16 @@ extern uint16_t           BandGap;
 
 int intpol(int x, uint8_t idx);
 int expo(int x, int k);
-int applyCurve(int x, int8_t idx);
+
+#if defined(CURVES)
+  #if defined(PCBTARANIS)
+    int applyCurve(int x, CurveRef & curve);
+  #else
+    int applyCurve(int x, int8_t idx);
+  #endif
+#else
+  #define applyCurve(x, idx) (x)
+#endif
 
 #if defined(PCBTARANIS)
   int applyCustomCurve(int x, uint8_t idx);