Mixer code moved to a separate file

radio/src/maths.cpp

@@ -36,6 +36,102 @@
 
 #include "opentx.h"
 
+#if !defined(CPUARM)
+// #define CORRECT_NEGATIVE_SHIFTS
+// open.20.fsguruh; shift right operations do the rounding different for negative values compared to positive values
+// so all negative divisions round always further down, which give absolute values bigger compared to a usual division
+// this is noticable on the display, because instead of -100.0 -99.9 is shown; While in praxis I doublt somebody will notice a
+// difference this is more a mental thing. Maybe people are distracted, because the easy calculations are obviously wrong
+// this define would correct this, but costs 34 bytes code for stock version
+
+// currently we set this to active always, because it might cause a fault about 1% compared positive and negative values
+// is done now in makefile
+
+int16_t calc100to256_16Bits(int16_t x) // return x*2.56
+{
+    // y = 2*x + x/2 +x/16-x/512-x/2048
+    // 512 and 2048 are out of scope from int8 input --> forget it
+#ifdef CORRECT_NEGATIVE_SHIFTS
+    int16_t res=(int16_t)x<<1;
+    //int8_t  sign=(uint8_t) x>>7;
+    int8_t sign=(x<0?1:0);
+
+    x-=sign;
+    res+=(x>>1);
+    res+=sign;
+    res+=(x>>4);
+    res+=sign;
+    return res;
+#else
+    return ((int16_t)x<<1)+(x>>1)+(x>>4);
+#endif
+}
+
+int16_t calc100to256(int8_t x) // return x*2.56
+{
+  return calc100to256_16Bits(x);
+}
+
+int16_t calc100toRESX_16Bits(int16_t x) // return x*10.24
+{
+#ifdef CORRECT_NEGATIVE_SHIFTS
+  int16_t res= ((int16_t)x*41)>>2;
+  int8_t sign=(x<0?1:0);
+  //int8_t  sign=(uint8_t) x>>7;
+  x-=sign;
+  res-=(x>>6);
+  res-=sign;
+  return res;
+#else
+  // return (int16_t)x*10 + x/4 - x/64;
+  return ((x*41)>>2) - (x>>6);
+#endif
+}
+
+int16_t calc100toRESX(int8_t x) // return x*10.24
+{
+  return calc100toRESX_16Bits(x);
+}
+
+// return x*1.024
+int16_t calc1000toRESX(int16_t x) // improve calc time by Pat MacKenzie
+{
+  // return x + x/32 - x/128 + x/512;
+  int16_t y = x>>5;
+  x+=y;
+  y=y>>2;
+  x-=y;
+  return x+(y>>2);
+}
+
+int16_t calcRESXto1000(int16_t x)  // return x/1.024
+{
+// *1000/1024 = x - x/32 + x/128
+  return (x - (x>>5) + (x>>7));
+}
+
+int8_t calcRESXto100(int16_t x)
+{
+  return (x*25) >> 8;
+}
+#endif
+
+#if defined(HELI) || defined(FRSKY_HUB)
+uint16_t isqrt32(uint32_t n)
+{
+  uint16_t c = 0x8000;
+  uint16_t g = 0x8000;
+
+  for (;;) {
+    if ((uint32_t)g*g > n)
+      g ^= c;
+    c >>= 1;
+    if(c == 0)
+      return g;
+    g |= c;
+  }
+}
+#endif
 
 /*
   Division by 10 and rounding or fixed point arithmetic values