Arduino sleep mode!! NEED HELP!!

Projects General Guidance
1

Hi guys,

I was wondering how to put the Arduino to sleep and what happens in the sleep mode. I'm using the SLEEP_MODE_PWR_DOWN, I believe this is the complete power down? If I'm wrong please correct me.

So I was making a project in which I want to put the Arduino to complete power down mode, where I don't want it to do anything. So to experiment how this sleep mode works with the Arduino I tried to make a sketch in which I trigger the sleep mode 5 seconds after getting into the loop. Also I have the built-in led on pin 13 turned on. I wanted to see if the led would turn off automatically as the Arduino jumps into the sleep mode. Unfortunately, the led doesn't turn off by itself. It seemed as if I had to write the code to turn off the led before going into the sleep mode and turn it back on after waking up. I forgot to mention that I'm using Interrupt on pin 2 to wake up the Arduino from sleep.

So does that mean I'll have to turn off all devices I wanted to stop working during the sleep mode manually (I mean with extra lines of code obviously, like I did with the led in this sketch below)? Is there no way for the Arduino to automatically turn off everything in power down mode?

This is my experiment sketch.

#include <avr/sleep.h>
#define interruptPin 2


unsigned long curtime1 = 0;
unsigned long prevtime1 = 0;
unsigned long curtime2 = 0;
unsigned long prevtime2 = 0;
int interval1 = 5000;
int interval2 = 500;

void setup()
{
  Serial.begin(115200);
  pinMode(LED_BUILTIN, OUTPUT);
  pinMode(interruptPin, INPUT_PULLUP);
  digitalWrite(LED_BUILTIN, HIGH);
}

void loop()
{
  curtime1 = millis();
  curtime2 = millis();
  if ((curtime1 - prevtime1) >= interval1)
  {
    Serial.println("Going to sleep now!!");
    prevtime1 = curtime1;
    going_to_sleep();
  }
  if ((curtime2 - prevtime2) >= interval2)
  {
    Serial.println("im still running");           //To check via serial monitor if the loop is still running while on sleep.
    prevtime2 = curtime2;
  }
}

void going_to_sleep()
{
  sleep_enable();
  attachInterrupt(0, wakeUp, LOW);
  set_sleep_mode(SLEEP_MODE_PWR_DOWN);
  //digitalWrite(LED_BUILTIN, LOW);                     //To turn off led before going to sleep
  delay(1000);
  sleep_cpu();
  Serial.println("just woke up!!");
  //digitalWrite(LED_BUILTIN, HIGH);                    //To turn on led after waking up
}

void wakeUp()
{
  Serial.println("Interrupt Fired");
  sleep_disable();
  detachInterrupt(0);
}
2

You do need to turn stuff of manually.

The lowpower library or the processor cannot know which devices you have connected to the pins and cannot know what to do to turn the devices off.

And neither is there any standard way of turning an attached device off or putting into a low current sleep mode.

3

srnet:
You do need to turn stuff of manually.

The lowpower library or the processor cannot know which devices you have connected to the pins and cannot know what to do to turn the devices off.

And neither is there any standard way of turning an attached device off or putting into a low current sleep mode.

Well I thought the same but I had my doubts. Now that's cleared, I can continue my work. Thank you for your time.

4

I'm using the SLEEP_MODE_PWR_DOWN, I believe this is the complete power down?

No. The processor is powered but the clocks are stopped. Importantly, memory and configuration is maintained.

The processor can still be awakened by certain interrupts, like the watchdog timer.

It is really important to read the appropriate section of the processor data sheet for questions like this.

5

jremington:
No. The processor is powered but the clocks are stopped. Importantly, memory and configuration is maintained.

The processor can still be awakened by certain interrupts, like the watchdog timer.

It is really important to read the appropriate section of the processor data sheet for questions like this.

Yes, I will check the datasheet. Thank you for this information.