Example Code for AVR-Low Power and Wakeup
Last revision 2025/12/19
This article presents example code for AVR microcontrollers focused on low power techniques and efficient wakeup using interrupts. Readers will find guidance on hardware preparation, software setup, and a detailed code walkthrough for setting alarms and managing power effectively.
Hardware Preparation
- DFR0216-2 DFRduino UNO R3 with IO Expansion Shield and USB Cable A-B x 1
- DFR0819 Fermion: DS3231 RTC Module x 1
- FIT0916-FF DuPont Wires x5
Software Preparation
- Download Arduino IDE: Click to download Arduino IDE
- Download the DFRobot_DS323X library: DFRobot_DS323X library
- About how to install the library?
Wiring Diagram
Ensure the INT pin is connected to the correct interrupt pin of the main control board (D2 for UNO).
Sample Code
/*!
* @file lowPowerAndWakeUp.ino
* @brief Set alarm, and use interrput pin to trigger MCU wake up
* @n Experiment phenomenon: Set the alarm clock to trigger at a specified time.
* @n Connect SQW pin with DIGITALPIN2.
* @n Print information on serial port after the alarm clock is triggered.
* @n This demo only works on avr
* @copyright Copyright (c) 2010 DFRobot Co.Ltd (http://www.dfrobot.com)
* @licence The MIT License (MIT)
* @author [LuoYufeng]([email protected])
* @version V0.1
* @date 2021-2-23
* @url https://github.com/DFRobot/DFRobot_DS323X
*/
#include "DFRobot_DS323X.h"
#include <avr/sleep.h>
volatile int8_t alarmFlag = 0;
DFRobot_DS323X rtc;
int t = 0;
void setup(void)
{
Serial.begin(9600);
/*Wait for the chip to be initialized completely, and then exit*/
while(rtc.begin() != true){
Serial.println("failed to init chip, please check if the chip connection is correct. ");
delay(1000);
}
/*!
*@brief Set the value of pin sqw
*@param mode eSquareWave_OFF = 0x1C // Not output square wave, enter interrupt mode
*@n eSquareWave_1Hz = 0x00 // 1Hz square wave
*@n eSquareWave_1kHz = 0x08 // 1kHz square wave
*@n eSquareWave_4kHz = 0x10 // 4kHz square wave
*@n eSquareWave_8kHz = 0x18 // 8kHz square wave
*/
rtc.writeSqwPinMode(rtc.eSquareWave_OFF);
rtc.enableAlarm1Int();
//rtc.disableAlarm1Int();
//rtc.enableAlarm2Int();
rtc.disableAlarm2Int();
//rtc.setHourSystem(); //set hour system of time, e24hours,e12hours, default is the 24 hours mode.
/*!
*@brief Set alarm clock
*@param alarmType Alarm clock working mode typedef enum{
*@n eEverySecond,
*@n eSecondsMatch,
*@n eSecondsMinutesMatch,
*@n eSecondsMinutesHoursMatch,
*@n eSecondsMinutesHoursDateMatch,
*@n eSecondsMinutesHoursDayMatch, //Alarm1
*@n eUnknownAlarm1
*@n }eAlarm1Types_t;
*@param days Alarm clock Day (day)
*@param hours Alarm clock Hour (hour)
*@param minutes Alarm clock Minute (minute)
*@param seconds Alarm clock Second (second)
*/
rtc.setAlarm1(rtc.eSecondsMatch,/*date,0-30*/1,/*hour,0-23*/0,/*minute,0-59*/0,/*second,0-59*/15);//Alarm1
/*!
*@brief Set alarm clock
*@param alarmType Alarm clock working mode typedef enum{
*@n eEveryMinute,
*@n eMinutesMatch,
*@n eMinutesHoursMatch,
*@n eMinutesHoursDateMatch,
*@n eMinutesHoursDayMatch, //Alarm2
*@n eUnknownAlarm2
*@n }eAlarm2Types_t;
*@param days Alarm clock Day (day)
*@param hours Alarm clock Hour (hour)
*@param minutes Alarm clock Minute (minute)
*/
//rtc.setAlarm2(rtc.eEveryMinute,/*date,0-30*/1,/*hour,1-12 in 12hours,0-23 in 24hours*/0,/*minute,0-59*/0);//Alarm2
rtc.setTime(/*year,1900-2100*/2021, /*mouth,1-12*/2, /*date,1-31*/28, /*hour,0-23*/23,/*minute,0-59*/59,/*second,0-59*/55);//Set Set initial time .
#if defined(ESP32) || defined(ESP8266)||defined(ARDUINO_SAM_ZERO)
attachInterrupt(digitalPinToInterrupt(D6)/*Query the interrupt number of the D6 pin*/,interrupt,FALLING);
#else
/* The Correspondence Table of AVR Series Arduino Interrupt Pins And Terminal Numbers
* ---------------------------------------------------------------------------------------
* | | DigitalPin | 2 | 3 | |
* | Uno, Nano, Mini, other 328-based |--------------------------------------------|
* | | Interrupt No | 0 | 1 | |
* |-------------------------------------------------------------------------------------|
* | | Pin | 2 | 3 | 21 | 20 | 19 | 18 |
* | Mega2560 |--------------------------------------------|
* | | Interrupt No | 0 | 1 | 2 | 3 | 4 | 5 |
* |-------------------------------------------------------------------------------------|
* | | Pin | 3 | 2 | 0 | 1 | 7 | |
* | Leonardo, other 32u4-based |--------------------------------------------|
* | | Interrupt No | 0 | 1 | 2 | 3 | 4 | |
* |--------------------------------------------------------------------------------------
*/
/* The Correspondence Table of micro:bit Interrupt Pins And Terminal Numbers
* ---------------------------------------------------------------------------------------------------------------------------------------------
* | micro:bit | DigitalPin |P0-P20 can be used as an external interrupt |
* | (When using as an external interrupt, |---------------------------------------------------------------------------------------------|
* |no need to set it to input mode with pinMode)|Interrupt No|Interrupt number is a pin digital value, such as P0 interrupt number 0, P1 is 1 |
* |-------------------------------------------------------------------------------------------------------------------------------------------|
*/
attachInterrupt(/*Interrupt No*/0,interrupt,FALLING);//Enable the external interrupt 0, connect INT1/2 to the digital pin of the main control:
//UNO(2), Mega2560(2), Leonardo(3), microbit(P0).
#endif
/*!
*@brief Set avr sleep mode
*/
set_sleep_mode (SLEEP_MODE_PWR_DOWN);
sleep_cpu();
sleep_enable();
}
void loop() {
if(alarmFlag == 1){
/*!
*@brief Judge if the alarm clock is triggered
*@return eNoTrigger // No alarm is triggered
*@n eAlarm1Trigger // Alarm1 is triggered
*@n eAlarm2Trigger // Alarm2 is triggered
*@n eAllTrigger // All alarms are triggered
*/
if (rtc.isAlarmTrig() == rtc.eAlarm1Trigger){ // If the alarm bit is set
Serial.println("Alarm1 clock is triggered.");
/*!
*@brief Clear trigger flag
*/
rtc.clearAlarm();
}else if (rtc.isAlarmTrig() == rtc.eAlarm2Trigger){
Serial.println("Alarm2 clock is triggered.");
rtc.clearAlarm();
}else if (rtc.isAlarmTrig() == rtc.eAllTrigger){
Serial.println("Both Alarm clocks are triggered.");
rtc.clearAlarm();
}
alarmFlag = 0;
while (t < 10){
Serial.print(rtc.getYear(), DEC);
Serial.print('/');
Serial.print(rtc.getMonth(), DEC);
Serial.print('/');
Serial.print(rtc.getDate(), DEC);
Serial.print(" (");
Serial.print(rtc.getDayOfWeek());
Serial.print(") ");
Serial.print(rtc.getHour(), DEC);
Serial.print(':');
Serial.print(rtc.getMinute(), DEC);
Serial.print(':');
Serial.print(rtc.getSecond(), DEC);
Serial.print(' ');
/*if rtc works in 24hours mode,this function doesn't print anything*/
Serial.print(rtc.getAMorPM());
Serial.println();
delay(1000);
t = t + 1;
}
t = 0;
}
else
delay(1000);
/*!
*@brief Judge if it is power-down
*@return if return true, power-down, time needs to reset; false, work well
*/
if (rtc.isLostPower()) {
Serial.println("RTC lost power, please reset the time!");
}
sleep_enable();
//energy.PowerDown();
}
void interrupt(){
alarmFlag = 1;
sleep_disable();
}
Result
Wake up UNO at regular intervals and print the time information.
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