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docs/esp32/quickref: Refine deep-sleep power-saving notes. 

This attempts to better explain how pull-ups and pull-downs operate in
deep-sleep mode.
This commit is contained in:
Jonathan Hogg 2022-03-07 09:15:05 +00:00 committed by Damien George
parent 94a9b50668
commit 5887dfeea6
1 changed files with 22 additions and 8 deletions
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30
docs/esp32/quickref.rst
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@ -186,8 +186,7 @@ Notes:
* Pins 34-39 are input only, and also do not have internal pull-up resistors
* The pull value of some pins can be set to ``Pin.PULL_HOLD`` to reduce power
consumption during deepsleep.
* See :ref:`Deep_sleep_Mode` for a discussion of pin behaviour during sleep
There's a higher-level abstraction :ref:`machine.Signal <machine.Signal>`
which can be used to invert a pin. Useful for illuminating active-low LEDs
@ -508,6 +507,8 @@ See :ref:`machine.WDT <machine.WDT>`. ::
wdt = WDT(timeout=5000)
wdt.feed()
.. _Deep_sleep_mode:
Deep-sleep mode
---------------
@ -527,15 +528,28 @@ Notes:
* Calling ``deepsleep()`` without an argument will put the device to sleep
indefinitely
* A software reset does not change the reset cause
* There may be some leakage current flowing through enabled internal pullups.
To further reduce power consumption it is possible to disable the internal pullups::
p1 = Pin(4, Pin.IN, Pin.PULL_HOLD)
Some ESP32 pins (0, 2, 4, 12-15, 25-27, 32-39) are connected to the RTC during
deep-sleep and can be used to wake the device with the ``wake_on_`` functions in
the :mod:`esp32` module. The output-capable RTC pins (all except 34-39) will
also retain their pull-up or pull-down resistor configuration when entering
deep-sleep.
After leaving deepsleep it may be necessary to un-hold the pin explicitly (e.g. if
it is an output pin) via::
If the pull resistors are not actively required during deep-sleep and are likely
to cause current leakage (for example a pull-up resistor is connected to ground
through a switch), then they should be disabled to save power before entering
deep-sleep mode::
p1 = Pin(4, Pin.OUT, None)
from machine import Pin, deepsleep
# configure input RTC pin with pull-up on boot
pin = Pin(2, Pin.IN, Pin.PULL_UP)
# disable pull-up and put the device to sleep for 10 seconds
pin.init(pull=None)
machine.deepsleep(10000)
Non-RTC GPIO pins will be disconnected by default on entering deep-sleep.
SD card
-------