MSP430 Workshop notes 2/27/2011

/*

  blinky430.c

*/
#include <msp430x20x3.h>

void main(void)
{
	// The watchdog timer will periodically reset the chip if we haven't poked it
	// Initialize the WDT (WDTPW) and turn that behavior off (WDTHOLD)
	WDTCTL = WDTPW + WDTHOLD;

	// Mark P1.0 as an output pin by setting P1DIR's LSB to 1
	P1DIR = P1DIR | 0x01;

	while (1)	// Infinite loop
	{
		// Flip LED state
		// Invert pin P1.0, port 1 bitwise XOR with 0000 0001
		P1OUT = P1OUT ^ 0x01;

		// Wait
		i = 20000;
		while ( i > 0 ) {
			i--;
		}
	}
}

/*

  pulse430.c

*/
#include <msp430x20x3.h>

// Constants for pulse width increment and cycle time (sum of LED on + off time)
#define INCR  1
#define CYCLE 250

void main(void)
{
	// The watchdog timer will periodically reset the chip if we haven't poked it
	// Initialize the WDT (WDTPW) and turn that behavior off (WDTHOLD)
	WDTCTL = WDTPW + WDTHOLD;

	// Mark P1.0 as an output pin by setting P1DIR's LSB to 1
	P1DIR = P1DIR | 0x01;

	// Starting value for the LED pulse width
	unsigned int width = 11;

	// Per-cycle pulse width delta (how much longer to stay lit each cycle)
	unsigned int incr = INCR;

	// Loop counter
	unsigned long i;

	while (1)	// Infinite loop
	{

		// == LED ON ==
		// Turn on pin P1.0, port 1 bitwise OR with 0000 0001
		P1OUT = P1OUT | 0x01;

		// Wait
		i = width;
		while ( i > 0 ) {
			i--;
		}

		// == LED OFF ==
		// Turn off pin P1.0, port 1 bitwise AND with 1111 1110
		P1OUT = P1OUT & 0xFE;

		// Wait out the remainder of the cycle
		i = CYCLE - width;
		while ( i > 0 ) {
			i--;
		}

		// == UPDATE PULSE WIDTH ==
		width += incr;

		// If we've hit the minimum or maximum pulse width, start moving the width
		// in the other direction
		if ( width >= CYCLE - 30 || width < 1) {
			incr = -incr;
		}

	}
}