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ESP32 ESP-IDF example illustrating how to go back to sleep from deep sleep wake stub
/*
* This sample illustrates how to go back to deep sleep from the
* deep sleep wake stub.
*
* Consider the use case of counting pulses from an external sensor,
* where the pulses arrive at a relatively slow rate.
*
* ESP32 is configured to go into deep sleep mode, and wake up from
* a GPIO pin connected to the external pulse source.
* Once the pulse arrives, ESP32 wakes up from deep sleep and runs
* deep sleep wake stub. This stub function is stored in RTC fast
* memory, so it can run without waiting for the whole firmware
* to be loaded from flash.
*
* This function (called wake_stub below) increments the pulse counter,
* stored in RTC_SLOW_MEM. This memory is also preserved when going
* into deep sleep. Then the wake stub decides whether to continue
* booting the firmware, or to go back to sleep. In this simple example,
* the stub starts firmware when the pulse counter reaches 100.
* Note: in real application, counting needs to be continued when the
* application has started, for example using the PCNT peripheral.
*
*/
#include <stdio.h>
#include <string.h>
#include "esp_deep_sleep.h"
#include "esp_attr.h"
#include "rom/rtc.h"
#include "rom/ets_sys.h"
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "soc/rtc_cntl_reg.h"
#include "soc/rtc_io_reg.h"
#include "soc/uart_reg.h"
#include "soc/timer_group_reg.h"
// Pin used for pulse counting
// GPIO0 is RTC_GPIO11 (see esp32_chip_pin_list_en.pdf)
#define PULSE_CNT_GPIO_NUM 0
#define PULSE_CNT_RTC_GPIO_NUM 11
#define PULSE_CNT_IS_LOW() \
((REG_GET_FIELD(RTC_GPIO_IN_REG, RTC_GPIO_IN_NEXT) \
& BIT(PULSE_CNT_RTC_GPIO_NUM)) == 0)
// Pulse counter value, stored in RTC_SLOW_MEM
static size_t RTC_DATA_ATTR s_pulse_count;
static size_t RTC_DATA_ATTR s_max_pulse_count;
// Function which runs after exit from deep sleep
static void RTC_IRAM_ATTR wake_stub();
void app_main(void)
{
if (rtc_get_reset_reason(0) == DEEPSLEEP_RESET) {
printf("Wake up from deep sleep\n");
printf("Pulse count=%d\n", s_pulse_count);
} else {
printf("Not a deep sleep wake up\n");
}
s_pulse_count = 0;
s_max_pulse_count = 20;
printf("Going to deep sleep in 1 second\n");
printf("Will wake up after %d pulses\n", s_max_pulse_count);
vTaskDelay(1000/portTICK_PERIOD_MS);
// Set the wake stub function
esp_set_deep_sleep_wake_stub(&wake_stub);
// Wake up on low logic level
ESP_ERROR_CHECK( esp_deep_sleep_enable_ext1_wakeup(
1LL << PULSE_CNT_GPIO_NUM, ESP_EXT1_WAKEUP_ALL_LOW) );
// Enter deep sleep
esp_deep_sleep_start();
}
static const char RTC_RODATA_ATTR wake_fmt_str[] = "count=%d\n";
static const char RTC_RODATA_ATTR sleep_fmt_str[] = "sleeping\n";
static void RTC_IRAM_ATTR wake_stub()
{
// Increment the pulse counter
s_pulse_count++;
// and print the pulse counter value:
ets_printf(wake_fmt_str, s_pulse_count);
if (s_pulse_count >= s_max_pulse_count) {
// On revision 0 of ESP32, this function must be called:
esp_default_wake_deep_sleep();
// Return from the wake stub function to continue
// booting the firmware.
return;
}
// Pulse count is <s_max_pulse_count, go back to sleep
// and wait for more pulses.
// Wait for pin level to be high.
// If we go to sleep when the pin is still low, the chip
// will wake up again immediately. Hardware doesn't have
// edge trigger support for deep sleep wakeup.
do {
while (PULSE_CNT_IS_LOW()) {
// feed the watchdog
REG_WRITE(TIMG_WDTFEED_REG(0), 1);
}
// debounce, 10ms
ets_delay_us(10000);
} while (PULSE_CNT_IS_LOW());
// Print status
ets_printf(sleep_fmt_str);
// Wait for UART to end transmitting.
while (REG_GET_FIELD(UART_STATUS_REG(0), UART_ST_UTX_OUT)) {
;
}
// Set the pointer of the wake stub function.
REG_WRITE(RTC_ENTRY_ADDR_REG, (uint32_t)&wake_stub);
// Go to sleep.
CLEAR_PERI_REG_MASK(RTC_CNTL_STATE0_REG, RTC_CNTL_SLEEP_EN);
SET_PERI_REG_MASK(RTC_CNTL_STATE0_REG, RTC_CNTL_SLEEP_EN);
// A few CPU cycles may be necessary for the sleep to start...
while (true) {
;
}
// never reaches here.
}
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