88 lines
4.9 KiB
Markdown
88 lines
4.9 KiB
Markdown
# Deep Sleep Example
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(See the README.md file in the upper level 'examples' directory for more information about examples.)
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The [deep sleep mode](https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/system/sleep_modes.html#sleep-modes) of the ESP32 is a power saving mode that causes the CPU, majority of RAM, and digital peripherals that are clocked from APB_CLK to be powered off. Deep sleep mode can be exited using one of multiple [wake up sources](https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/system/sleep_modes.html#wakeup-sources). This example demonstrates how to use the [`esp_sleep.h`](https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/system/sleep_modes.html#api-reference) API to enter deep sleep mode, then wake up form different sources.
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The following wake up sources are demonstrated in this example (refer to the [Wakeup Sources documentation](https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/system/sleep_modes.html#wakeup-sources) for more details regarding wake up sources):
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1. **Timer:** An RTC timer that can be programmed to trigger a wake up after a preset time. This example will trigger a wake up every 20 seconds.
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2. **EXT1:** External wake up 1 which is tied to multiple RTC GPIOs. This example use GPIO2 and GPIO4 to trigger a wake up with any one of the two pins are HIGH.
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3. **Touch:** Touch pad sensor interrupt. This example uses touch pads connected to GPIO32, GPIO33 in ESP32 or GPIO9 in ESP32-S2 to trigger a wake up when any of the pads are pressed.
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4. **ULP:** Ultra Low Power Coprocessor which can continue to run during deep sleep. This example utilizes the ULP and constantly sample the chip's temperature and trigger a wake up if the chips temperature exceeds ~5 degrees Celsius.
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Note: Some wake up sources can be disabled via configuration (see section on [project configuration](#Configure-the-project))
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In this example, the `CONFIG_BOOTLOADER_SKIP_VALIDATE_IN_DEEP_SLEEP` Kconfig option is used, which allows you to reduce the boot time of the bootloader during waking up from deep sleep. The bootloader stores in rtc memory the address of a running partition and uses it when it wakes up. This example allows you to skip all image checks and speed up the boot.
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## How to use example
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### Hardware Required
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This example should be able to run on any commonly available ESP32 development board without any extra hardware if only **Timer** and **ULP** wake up sources are used. However, the following extra connections will be required for the remaining wake up sources.
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- **EXT1:** GPIO2 and GPIO4 should be connected to LOW to avoid floating pins. When triggering a wake up, connect one or both of the pins to HIGH. Note that floating pins may trigger a wake up.
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- **Touch:** GPIO32, GPIO33 in ESP32 or GPIO9 in ESP32-S2 should be connected to touch sensors (see [Touch Sensor Application Note](https://github.com/espressif/esp-iot-solution/blob/master/documents/touch_pad_solution/touch_sensor_design_en.md)).
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### Configure the project
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```
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idf.py menuconfig
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```
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* **Touch wake up** can be enabled/disabled via `Example configuration > Enable touch wake up`
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* **ULT wake up** can be enabled/disabled via `Example configuration > Enable temperature monitoring by ULP`
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Wake up sources that are unused or unconnected should be disabled in configuration to prevent inadvertent triggering of wake up as a result of floating pins.
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### Build and Flash
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Build the project and flash it to the board, then run monitor tool to view serial output:
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```
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idf.py -p PORT flash monitor
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```
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(Replace PORT with the name of the serial port to use.)
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(To exit the serial monitor, type ``Ctrl-]``.)
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See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.
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## Example Output
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On initial startup, this example will detect that this is the first boot and output the following low:
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```
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...
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I (304) cpu_start: Starting scheduler on PRO CPU.
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I (0) cpu_start: Starting scheduler on APP CPU.
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Not a deep sleep reset
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Enabling timer wakeup, 20s
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Enabling EXT1 wakeup on pins GPIO2, GPIO4
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Touch pad #8 average: 2148, wakeup threshold set to 2048.
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Touch pad #9 average: 2148, wakeup threshold set to 2048.
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Enabling touch pad wakeup
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Enabling ULP wakeup
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Entering deep sleep
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```
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The ESP32 will then enter deep sleep. When a wake up occurs, the ESP32 must undergo the entire boot process again. However the example will detect that this boot is due to a wake up and indicate the wake up source in the output log such as the following:
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```
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...
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I (304) cpu_start: Starting scheduler on PRO CPU.
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I (0) cpu_start: Starting scheduler on APP CPU.
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Wake up from timer. Time spent in deep sleep: 20313ms
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ULP did 110 temperature measurements in 20313 ms
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Initial T=87, latest T=87
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Enabling timer wakeup, 20s
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Enabling EXT1 wakeup on pins GPIO2, GPIO4
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Touch pad #8 average: 2149, wakeup threshold set to 2049.
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Touch pad #9 average: 2146, wakeup threshold set to 2046.
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Enabling touch pad wakeup
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Enabling ULP wakeup
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Entering deep sleep
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```
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