adding led3.c

Makefile

@@ -4,7 +4,7 @@ CFLAGS 	= -Os -Wall -g -mmcu=msp430x2012
 LD 	= $(CC)
 LDFLAGS =
 
-PROGRAMS = led1.elf led2.elf
+PROGRAMS = led1.elf led2.elf led3.elf
 
 .PHONY : clean distclean
 
@@ -12,6 +12,7 @@ all : $(PROGRAMS)
 
 led1.elf : led1.o
 led2.elf : led2.o
+led3.elf : led3.o
 
 %.elf :
 	$(LD) -o $@ $^

led3.c

@@ -0,0 +1,54 @@
+
+#include <msp430.h>
+#include <legacymsp430.h>
+
+#define R_LED  BIT0
+#define G_LED  BIT6
+
+#define N_STATES 4
+
+int state = 0;
+
+void update(void) {
+
+	state = (state + 1) % N_STATES;
+
+	/* first bit set, enable red */
+	if (state & 0x1)
+		P1OUT |= R_LED;
+	else
+		P1OUT &= ~R_LED;
+
+	/* second bit set, enable green */
+	if (state & 0x2)
+		P1OUT |= G_LED;
+	else
+		P1OUT &= ~G_LED;
+}
+
+int main(void) {
+
+	/* Set watchdog timer to interupt at 32ms interval. */
+	WDTCTL = WDT_MDLY_32;
+
+	/* set direction to output on both leds */
+	P1DIR |= (R_LED | G_LED);
+
+	P1OUT = 0x0;
+
+	/* enable interrupt */
+	IE1 |= WDTIE;
+	_BIS_SR(LPM0_bits + GIE);
+
+	for(;;);
+
+	return 0;
+}
+
+interrupt(WDT_VECTOR) main_isr(void) {
+
+	static int cntr = 0;
+
+	if ((cntr++ % 30) == 0)
+		update();
+}