8051 Encoder

encoder.c

/*!
 * \file encoder.c
 *
 * Date: 22/01/2019
 */

#include <stdio.h>
#include <8052.h>


/*! \brief Encoder "absolute" position. */
int ABS_POS;

/* A limit switch should be used to set a zero position. */


/*!
 * \brief Init serial port at 19200.
 */
void
initSio ()
{
  TMOD &= 0x0F;
  TMOD |= 0x20;
  TCON = 0x41;
  TH1 = 0xFD;
  SCON = 0x50;
}


/*!
 * \brief For SDCC printf.
 */
int
putchar (int c)
{
  SBUF = c;
  while (!TI);
  TI = 0;
  return 0;
}


/*!
 * \bruief Enables interrupt on P3_2 falling edge transition.
 */
void
interruptSetupEx0 ()
{
  EA = 1; /* Enable all interrupts. */
  EX0 = 1; /* Enable interrupt on pin P3_2. */
  IT0 = 1; /* Falling edge. */
}


/*!
 * \brief ISR for external interrupt INT0.
 */
void
ISR_ex0 (void) __interrupt 0
{
  if (P3_3 = 1) ABS_POS++;
  else ABS_POS--;
  //printf("called");
  /* (P3_3 = 1 ? ABS_POS++: ABS_POS--); This doesn't work and I don't know why :-). */
}


void
main ()
{
  P3_2 = 1; /* Input (interrupt trigger). */
  P3_3 = 1; /* Input (direction detection). */
  ABS_POS = 0;
  initSio ();
  interruptSetupEx0 (); /* From this point interrupt is enabled. */
  while(1)
  {
    printf ("Position %d\n\r\f", ABS_POS);
    for (unsigned int a = 0; a < 60000; a++) /* Delay. */
    {
      for (int b = 0; b < 10; b++);
    }; /* Delay line. */
  }
}

/* EOF */