Programming the Arduino

This is a collection of links and tips on how to program the Arduino. Main source is the Arduino.cc Code Library.

Push buttons

• How and Why to avoid using delay()

Sound Generation

• Generating musical signals using freqout()

Fast Division

fast division by 10

• Fast division by 10

Fast division by 10

void divmod10(uint32_t in, uint32_t &div, uint32_t &mod)
{
  uint32_t x=(in>>1); // div = in/10 <==> div = ((in/2)/5)
        uint32_t q=x;

        q= (q>>8) + x;
        q= (q>>8) + x;
        q= (q>>8) + x;
        q= (q>>8) + x + 1;

        x= q;
        q= (q>>1) + x;
        q= (q>>3) + x;
        q= (q>>1) + x;

        div = (q >> 3);
        mod = in - (((div << 2) + div) << 1);
}

This was the earlier version:

Fast division by 10 early version

void divmod10(uint32_t in, uint32_t &div, uint32_t &mod)
{
  // q = in * 0.8;
  uint32_t q = (in >> 1) + (in >> 2);
  q = q + (q >> 4);
  q = q + (q >> 8);
  q = q + (q >> 16);  // not needed for 16 bit version

  // q = q / 8;  ==> q =  in *0.1;
  q = q >> 3;
  
  // determine error
  uint32_t  r = in - ((q << 3) + (q << 1));   // r = in - q*10; 
  div = q + (r > 9);
  if (r > 9) mod = r - 10;
  else mod = r;
}

Home Automation

• Internet of Things at Souliss

Doing Two things at Once

• Blink without delay()

• Replacing delay() with IsTime()

Logic Probe

• Op-Amp-based logic probe No Arduino needed for this.