Arduino code to get clean values from even the noisiest and silliest rotary encoder

read_rotary.c

// From https://www.best-microcontroller-projects.com/rotary-encoder.html

static uint8_t prevNextCode = 0;
static uint16_t store=0;

int8_t read_rotary() {
  static int8_t rot_enc_table[] = {0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0};

  prevNextCode <<= 2;
  if (digitalRead(RIGHT_PIN)) prevNextCode |= 0x02;
  if (digitalRead(LEFT_PIN)) prevNextCode |= 0x01;
  prevNextCode &= 0x0f;

   // If valid then store as 16 bit data.
   if  (rot_enc_table[prevNextCode] ) {
      store <<= 4;
      store |= prevNextCode;
      //if (store==0xd42b) return 1;
      //if (store==0xe817) return -1;
      if ((store&0xff)==0x2b) return -1;
      if ((store&0xff)==0x17) return 1;
   }
   return 0;
}