deep_sleep_demo

# Deep Sleep Demo

Puts the chip into deep sleep and wakes it with a button or a 30-second timer, reporting the wake-up
cause on each boot.

## What it demonstrates

- Keeping a boot counter in RTC memory (`RTC_DATA_ATTR`), which survives deep sleep
- Finding out why the chip started with `idfxx::sleep::wakeup_cause()`
- Finding out which pin woke the chip with `idfxx::sleep::ext1_wakeup_status()`
- Entering deep sleep with `idfxx::sleep::deep_sleep()`, armed with two wake-up sources: a pin and a
  timer (`idfxx::sleep::timer_wake`)
- Choosing the pin wake-up source for each chip: `idfxx::sleep::deep_sleep_gpio_wake` on the ESP32-C3 and
  ESP32-C6, which keeps the pin's internal pull-up on during sleep, and `idfxx::sleep::ext1_wake` on the others
- Selecting the EXT1 low-level trigger by target: `ext1_mode::all_low` on the ESP32, `ext1_mode::any_low`
  on the others

The example uses the exception-based API (`CONFIG_COMPILER_CXX_EXCEPTIONS=y` in `sdkconfig.defaults`).

## Hardware required

- Any ESP32-series development board
- On the ESP32-C3 and ESP32-C6, a push button on GPIO 0 that pulls the pin low when pressed

The example wakes on a button that pulls its pin low. It uses the board's BOOT button where that
button can wake the chip from deep sleep: GPIO 0 on the ESP32, ESP32-S2 and ESP32-S3, and GPIO 9 on
the ESP32-H2. These BOOT buttons have an external pull-up, so no extra parts are needed.

On the ESP32-C3 and ESP32-C6, the BOOT button is on GPIO 9, which can't wake these chips from deep
sleep. Connect a push button between GPIO 0 and GND instead; the example keeps the pin's internal
pull-up on while the chip sleeps.

To use a different pin, change `WAKE_PIN` in `main/main.cpp`. To change the timer, change
`SLEEP_INTERVAL`.

## How to use

Create a project from this example:

```bash
idf.py create-project-from-example "cleishm/idfxx_sleep:deep_sleep_demo"
cd deep_sleep_demo
```

Then build and flash it, then watch the serial output:

```bash
idf.py set-target esp32
idf.py -p PORT flash monitor
```

Replace `esp32` with your target and `PORT` with your board's serial port. Press `Ctrl-]` to exit the
monitor.

After a cold boot, the chip reports the boot and goes to deep sleep. Press the button to wake it, or
wait 30 seconds for the timer. Waking from deep sleep restarts the application, so each wake prints
the boot count and what woke the chip, then sleeps again. If your board connects to the computer
through the chip's own USB port rather than a USB-to-UART bridge, the serial connection drops while
the chip sleeps.