Analog Comparator Wakeup

Other Hardware 3rd Party Boards
1

Hello All,

I am looking for a bit of assistance to get my microcontroller to fall asleep and wake-up due to an interrupt from the analog comparator. The idea here is that I have an accelerometer connected to an analog input PD6 (AIN0) D6 and a reference voltage on PD7 (AIN1) D7. This way when the device is moved it will wake-up.

I have started with a example program from Nick Gammon. I tested using the ISR to blink the LED as the accelerometer value rises over the threshold of D7 (1.5V).

I have been looking at some of the examples programs for putting the Arduino to sleep.

Here is a snapshot of my code.

/* 
 *  Date: 2/15/16
 *  Example Sleep Program using the Analog Compator
 *  Originally based on Nick Gammon's Analog Sleep Comparator Program
 *  Atmel328p processor with accelerometer connected to PD6 (AIN0), Digital Pin 6 on Arduino IDE
 *  Pin PD7 (AIN1), Digital Pin 7 on Arduino IDE, has a voltage divider set to 1.5 V.
 *
 */

#include <avr/interrupt.h>
#include <avr/power.h>
#include <avr/sleep.h>
#include <avr/io.h>                
int ledPin = 4;
volatile boolean triggered;

void setup(void)
{
    pinMode(ledPin,OUTPUT);     // set LED pin (D4) as an output
    digitalWrite(ledPin,LOW);   // turn LED on (active low)

    ADCSRB = 0;           // (Disable) ACME: Analog Comparator Multiplexer Enable
    ACSR =  bit (ACI)     // (Clear) Analog Comparator Interrupt Flag
      | bit (ACIE)        // Analog Comparator Interrupt Enable
      | bit (ACIS1);      // ACIS1, ACIS0: Analog Comparator Interrupt Mode Select (trigger on falling edge)
     triggered = 0;
}
              
void loop(void)
{
    if (triggered == true)
    {
    digitalWrite(ledPin,LOW);   // turn LED on (active low)
    delay(3000); // wait to see the LED before sleeping again
    }
    sleepNow();
    
}
                
void sleepNow(void)
{
    triggered = false;
    digitalWrite(ledPin,HIGH);   // turn LED off (active low)
    // Choose our preferred sleep mode:
    set_sleep_mode(SLEEP_MODE_IDLE);
    
    // Set sleep enable (SE) bit:
    sleep_enable();
    
    // Put the device to sleep:
    sleep_mode();
 
    // Upon waking up, sketch continues from this point.
    sleep_disable();
  
}          

ISR (ANALOG_COMP_vect)
  {
  triggered = true;
  }

Any help will be much appreciated. The goal here is to improve the battery life for this project.

Thanks,

NB

2

Also this was the original program I started with to learn about the analog comparator.