1.. _esp32-light-sleep-sample:
2
3ESP32 Light Sleep demo
4######################
5
6Overview
7********
8
9This example illustrates usage of light sleep mode. Unlike deep sleep mode,
10light sleep preserves the state of the memory, CPU, and peripherals. Execution
11of code on both CPUs is stopped when esp_light_sleep_start() function is called.
12When the chip exits light sleep mode, execution continues at the point where it
13was stopped, and esp_light_sleep_start() function returns.
14
15The example enables the following wakeup sources:
16
17* ``Timer``: wake up the chip in 2 seconds.
18* ``EXT0``: wake up the chip if a button attached to GPIO0 is pressed (i.e. if
19  GPIO0 goes low).
20
21Requirements
22************
23
24This example can be used with any ESP32 development board. Most boards have a
25button attached to GPIO0, often labelled BOOT. If the board does not have such
26button, an external button can be connected, along with a 10k pull-up resistor,
27and a 100nF capacitor to ground for debouncing.
28
29Building, Flashing and Running
30******************************
31
32.. zephyr-app-commands::
33   :zephyr-app: samples/boards/esp32/light_sleep
34   :board: esp32_devkitc_wroom
35   :goals: build flash
36   :compact:
37
38Sample Output
39=================
40ESP32 core output
41-----------------
42
43In the scenario below, the button attached to GPIO0 was pressed and held for
44about 500 ms, after the second wakeup from light sleep. The program has
45indicated the wakeup reason after each sleep iteration.
46
47.. code-block:: console
48
49   *** Booting Zephyr OS build zephyr-v3.1.0-3667-gb42e2b225ecf  ***
50
51   Entering light sleep
52   Returned from light sleep, reason: timer, t=3344 ms, slept for 2001 ms
53   Entering light sleep
54   Returned from light sleep, reason: timer, t=5354 ms, slept for 2000 ms
55   Entering light sleep
56   Returned from light sleep, reason: pin, t=5885 ms, slept for 521 ms
57   Waiting for GPIO0 to go high...
58   Entering light sleep
59   Returned from light sleep, reason: timer, t=8765 ms, slept for 2000 ms
60   Entering light sleep
61   Returned from light sleep, reason: timer, t=10776 ms, slept for 2001 ms
62   Entering light sleep
63
64Troubleshooting
65***************
66
67If pressing the button attached to GPIO0 does not affect program behavior,
68check DTR/RTS configuration in the serial monitor. This is not necessary for
69IDF monitor, but for other tools it might be necessary to set DTR and RTS line
70state to "disabled" or "de-asserted".
71