Hello,
I found this web page, Using the watchdog for both preventing failures and energy savings . I think this code should be useful for my application as I wanted a low power setup as well as some protection against code failures.
How can I add an external interrupt to wake the Arduino up from sleep? Below is the original code from the website as well as some of the external interrupt code (in bold).
#include <avr/wdt.h> // library for default watchdog functions
#include <avr/interrupt.h> // library for interrupts handling
#include <avr/sleep.h> // library for sleep
#include <avr/power.h> // library for power control
// how many times remain to sleep before wake up
// volatile to be modified in interrupt function
volatile int nbr_remaining;
// pin on which a led is attached on the board
#define led 13
int pin2 = 2;
void pin2Interrupt(void)
{
/* This will bring us back from sleep. */
/* We detach the interrupt to stop it from
* continuously firing while the interrupt pin
* is low.
*/
detachInterrupt(0);
}
// interrupt raised by the watchdog firing
// when the watchdog fires, this function will be executed
// remember that interrupts are disabled in ISR functions
// now we must check if the board is sleeping or if this is a genuine
// interrupt (hanging)
ISR(WDT_vect)
{
// Check if we are in sleep mode or it is a genuine WDR.
if(nbr_remaining > 0)
{
// not hang out, just waiting
// decrease the number of remaining avail loops
nbr_remaining = nbr_remaining - 1;
wdt_reset();
}
else
{
// must be rebooted
// configure
MCUSR = 0; // reset flags
// Put timer in reset-only mode:
WDTCSR |= 0b00011000; // Enter config mode.
WDTCSR = 0b00001000 | 0b000000; // clr WDIE (interrupt enable...7th from left)
// set WDE (reset enable...4th from left), and set delay interval
// reset system in 16 ms...
// unless wdt_disable() in loop() is reached first
// reboot
while(1);
}
}
// function to configure the watchdog: let it sleep 8 seconds before firing
// when firing, configure it for resuming program execution by default
// hangs will correspond to watchdog fired when nbr_remaining <= 0 and will
// be determined in the ISR function
void configure_wdt(void)
{
cli(); // disable interrupts for changing the registers
MCUSR = 0; // reset status register flags
// Put timer in interrupt-only mode:
WDTCSR |= 0b00011000; // Set WDCE (5th from left) and WDE (4th from left) to enter config mode,
// using bitwise OR assignment (leaves other bits unchanged).
WDTCSR = 0b01000000 | 0b100001; // set WDIE: interrupt enabled
// clr WDE: reset disabled
// and set delay interval (right side of bar) to 8 seconds
sei(); // re-enable interrupts
}
// Put the Arduino to deep sleep. Only an interrupt can wake it up.
void sleep(int ncycles)
{
nbr_remaining = ncycles; // defines how many cycles should sleep
// Set sleep to full power down. Only external interrupts or
// the watchdog timer can wake the CPU!
set_sleep_mode(SLEEP_MODE_PWR_DOWN);
// Turn off the ADC while asleep.
power_adc_disable();
while (nbr_remaining > 0){ // while some cycles left, sleep!
// Enable sleep and enter sleep mode.
sleep_mode();
// CPU is now asleep and program execution completely halts!
// Once awake, execution will resume at this point if the
// watchdog is configured for resume rather than restart
// When awake, disable sleep mode
sleep_disable();
// we have slept one time more
nbr_remaining = nbr_remaining - 1;
}
// put everything on again
power_all_enable();
}
void setup(){
/* Setup the pin direction. */
pinMode(pin2, INPUT);
// use led 13 and put it in low mode
pinMode(led, OUTPUT);
digitalWrite(led, LOW);
delay(1000);
// configure the watchdog
configure_wdt();
// blink twice
digitalWrite(led, HIGH);
delay(500);
digitalWrite(led, LOW);
delay(500);
digitalWrite(led, HIGH);
delay(500);
digitalWrite(led, LOW);
delay(500);
}
void loop(){
// sleep for a given number of cycles (here, 5 * 8 seconds) in lowest power mode
sleep(5);
// usefull stuff
// blink three times
digitalWrite(led, HIGH);
delay(500);
digitalWrite(led, LOW);
delay(500);
digitalWrite(led, HIGH);
delay(500);
digitalWrite(led, LOW);
delay(500);
digitalWrite(led, HIGH);
delay(500);
digitalWrite(led, LOW);
delay(500);
// now a real hang is happening: this will rebood the board
// after 8 seconds
// (at the end of the sleep, nrb_remaining = 0)
//while (1);
}
Where should I place attachInterrupt(0, pin2Interrupt, LOW); so the external interrupt works? I haven't been able to get this to work.
Thanks for any help