Sleep

There are several methods to make your device sleep. First we cover the basic sleep. Similar to delay() used in Arduino, sleep will yield your program until the time is over. Important is that the all microcontroller functions keep running. Also the LoRa, SigFox and LTE modems can be used directly (without re-attaching) after regular sleep.

import time

time.sleep(1) #sleep 1 second

time.sleep_ms(10) #sleep 10 milliseconds

time.sleep_us(10) #sleep 10 microseconds

import machine
machine.idle()

Power saving

To save power, we can also put the controller into sleep modes using the following examples.

Light sleep

The machine.sleep() command will put the controller into a light sleep mode. WiFi and BLE are switched off, but the main CPU and RAM are still running. the LoRa, SigFox and LTE modems are stopped as well and have to be re-initialized after wakeup. The controller will continue running the code after waking up. GPIO states are also conserved. Setting the second argument to True will restore the WiFi and BLE after wakeup.

import machine
import time
print("this will be printed before: " + str(time.ticks_ms()))
machine.sleep(1000*10, True)
print("this will be printed after 10 seconds: " str(time.ticks_ms()))

Deep sleep

Deepsleep disables, next to the lightsleep, the main CPU and RAM. This leaves only a low power coprocessor and RTC timer running. After waking up, the board will start again at boot.py, just like with pressing the reset button. The CPU counter (time.ticks()) will continue to count however! You can also leave the brackets empty to sleep indefinetely, until the reset button is pressed, the power is removed, or an external wake up signal (interrupt) is provided. Be aware that the LTE modem will remain switched on unless you actively switch off its power, or use its own power saving modes.

import machine
print("Wake up")
machine.deepsleep(1000) #deepsleep 1 second
print("this will never get printed!")

Wake up reason

Sometimes, we want to know the reason the board woke up, to differentiate the difference between pressing the reset button and waking up from sleep. We can also determine the time left on the sleep timer. Try the example below:

import machine
import time
(wake_reason, gpio_list) = machine.wake_reason()
print("Device running for: " + str(time.ticks_ms()) + "ms")
print("Remaining sleep time: " + str(machine.remaining_sleep_time()) + "ms" )
if wake_reason == machine.PWRON_WAKE:
    print("Woke up by reset button")
elif wake_reason == machine.PIN_WAKE:
    print("Woke up by external pin (external interrupt)")
    print(*gpio_list, sep=", ")
elif wake_reason == machine.RTC_WAKE:
    print("Woke up by RTC (timer ran out)")
elif wake_reason == machine.ULP_WAKE:
    print("Woke up by ULP (capacitive touch)")

machine.pin_sleep_wakeup(('P3', 'P4'), mode=machine.WAKEUP_ANY_HIGH, enable_pull=True)

machine.deepsleep(1000*60) #sleep for 1 minute
print("This will never be printed")

For the Pysense, Pytrack and Pyscan expansionboards, an additional sleep function is available. You can find out more about that here