/* Shaft.c */


/* Utility functions for monitoring the shaft encoders */


/* Functions for reading left and right "velocities" using PA7s pulse counter */

/* and an interrupt routine (in speed.icb) to catch pulses on PA0 */


void init_velocity()		/* Enable PA7 pulse counting and PA0 interrupt */

{ poke(0x1026,0b01010000);	/* PACTL  PA7 input, trigger on rising edge */

  poke(0x1027,0);		/* PACNT  init to 0 */

  left_clicks = 0;		/* Global referenced by interrupt routine */

  bit_clear(0x1021,0b10);	/* TCTL2 Assign values to the two lowest order bits */

  bit_set(  0x1021,0b01);	/*  of tctl2 without changing any other bits */

  bit_set(  0x1022,0b01);	/* TMSK1  enable IC3 interrupts */

}


int get_left_clicks()		/* Get the number of clicks and reset to 0 */

{ int clks = left_clicks;	/* If called at regular intervals this funciton returns */

  left_clicks = 0;		/*  the the left velocity in units of clicks per interval */

  return clks; }


int get_right_clicks()		/* Same as above for right Shaft encoder */

{ int clks = peek(0x1027);	/* PACNT is only an 8-bit register -- be sure to */

  poke(0x1027,0);		/*  call it often enough so that it dosen't overflow */

  return clks; }