bldc-1.c

#include "msp430.h"

/*
  BLDC motor driver ver1

  P2.0 P2.1 P2.2 go through cycle
  010
  011
  001
  101
  100
  110

  This pattern can be generated using initial state 010
  and xor mask 001, rotating latter left after each use

  Compiled using msp430-gcc 4.6.3

  aarmot 2013-01-19
*/

#define	OUTPUT_MASK	0b111
#define	INITIAL_BITS	0b010
#define	INITIAL_MASK	0b100

// Approximate period, measured in usec
#define	PERIOD		1000

unsigned char xormask = INITIAL_MASK;

void main(void)
{
	WDTCTL = WDTPW + WDTHOLD;	// Stop watchdog

	BCSCTL1 = CALBC1_1MHZ;		// Running at 1 MHz
	DCOCTL = CALDCO_1MHZ;

	P2DIR |= OUTPUT_MASK;		// Output direction
	P2OUT = INITIAL_BITS;

	TA0CCTL0 = CCIE;		// CCR0 interrupt enabled
	TA0CCR0 = PERIOD;
	TA0CTL = TASSEL_2 + MC_2;	// SMCLK, contmode
	__bis_SR_register(LPM0_bits + GIE);	// Enter LPM0 w/ interrupt
}

__attribute__((__interrupt__(TIMER0_A0_VECTOR)))
void Timer0_A(void)
{
	P2OUT ^= xormask;			// Toggle output
	xormask >>= 1;
	if(xormask == 0) xormask = INITIAL_MASK;
	TA0CCR0 += PERIOD;
}