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/*
Copyright (c) 2010 - Mike Szczys
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/
#include <msp430.h>
#define LED0 BIT0
#define LED1 BIT6
#define LED_DIR P1DIR
#define LED_OUT P1OUT
void initLEDs(void) {
LED_DIR |= LED0 + LED1; //Set LED pins as outputs
LED_OUT |= LED0 + LED1; //Turn on both LEDs
}
int main(void) {
WDTCTL = WDTPW + WDTHOLD; // Stop WDT
/*Halt the watchdog timer
According to the datasheet the watchdog timer
starts automatically after powerup. It must be
configured or halted at the beginning of code
execution to avoid a system reset. Furthermore,
the watchdog timer register (WDTCTL) is
password protected, and requires the upper byte
during write operations to be 0x5A, which is the
value associated with WDTPW.*/
initLEDs(); //Setup LEDs
BCSCTL3 |= LFXT1S_2; //Set ACLK to use internal VLO (12 kHz clock)
TACTL = TASSEL_1 | MC_1; //Set TimerA to use auxiliary clock in UP mode
TACCTL0 = CCIE; //Enable the interrupt for TACCR0 match
TACCR0 = 11999; /*Set TACCR0 which also starts the timer. At
12 kHz, counting to 12000 should output
an LED change every 1 second. Try this
out and see how inaccurate the VLO can be */
WRITE_SR(GIE); //Enable global interrupts
while(1) {
//Loop forever, interrupts take care of the rest
}
}
void __attribute__((interrupt (TIMERA0_VECTOR))) TIMERA0_ISR(void) {
LED_OUT ^= (LED0 + LED1); //Toggle both LEDs
}
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