divu5() and divu3(). Fast replacements for unsigned division by 3, 5, 6, 10, 15

Development Libraries
9

Nice work Tom!

I have some functions prototyped some time ago. can be used as starting point but can still be optimized further.

divu24, divu12, divu3600, for clock math

uint32_t div24(uint32_t in)
{
  return div3(in) >> 3;
}

uint32_t div12(uint32_t in)
{
  return div3(in) >> 2;
}

uint32_t div86400(uint32_t in)  // seconds to days
{
  return ((in >> 1) + (in >>2) + (in>>7) + (in>>11) + (in>>12) - (in>>15)) >> 16;
}

uint32_t div3600(uint32_t in)
{
  return div60(div60(in));
}

divu1000 - for millis/micros, millimeters to meters etc

some experimental code (to be optimized)

uint32_t div100(uint32_t in)  // cm to meters
{
  return div10(div10(in));
}

uint32_t div1000(uint32_t in)
{
  return ((in>>2) + (in>>8) + ((in>>1) + (in>>5) + (in>>8) + (in>>11) + (in>>12) + (in >>14) + (in >> 15)) >> 8) >> 8 ;
}

div29 (for ultrasonic sensors) see - PING duration to cm division / 29 optimized - Libraries - Arduino Forum -

some gonio related experiments (to be optimized)

uint32_t divPI(uint32_t in)
{
  uint32_t x = (in>>2) + (in>>4) + (in>>8) + (in>>9) - (in>>15) + (in >>17); // minus is correct
  return x;
}

uint32_t mulPI(uint32_t in)
{
  uint32_t x = (in<<1) + in + (in>>3) + (in>>6) + (in>>10);
  return x;
}

uint32_t degrees2radians(uint32_t in)
{
  uint32_t x = (in>>1) + (in>>5);
  x += (( (in>>1) + (in>>2) - (in>>3) + (in >>6) ) >>5);
  return x >> 5;
}

uint32_t radians2degrees(uint32_t in)
{
  uint32_t x = (in << 5) + (in<<4) + (in<<3) + in + (in>>2) + (in>>5) + (in>>7) + (in>>8) + (in>>9) + (in >>10);
  return x;
}

my div 13 code (not tested in detail)

uint32_t div13(uint32_t in)
{
  // powers 4,  7,8,9,11,12,16,  19,20,21,23,24,28
  uint32 t = in>>7 + in>>8 + in>>9 + in>>11 + in>>12 + in>>16;
  t = t + t>>12;
  return (in>>4) + t;
}