Light sleep wake-up via gpio on esp32

Question

I have a simple code for esp32 here. I can only use gpio pin number 35 on the board. So esp32 should go to light sleep and wake up on button press. When I run this program below, my esp32 goes into light sleep, but it doesn't wake up when the button is pressed. What's the problem? Any idea please? Thank you.

#include <esp_sleep.h>

void setup() {

  Serial.begin(115200);
  delay(2000);
  gpio_wakeup_enable(GPIO_NUM_35, GPIO_INTR_HIGH_LEVEL);
  esp_sleep_enable_gpio_wakeup();
  delay(2000); 
  Serial.println("Going to sleep now");
  delay(2000); 
  esp_light_sleep_start();
  delay(2000); 
  Serial.println("This will be NOT printed");

}

void loop() {
  delay(2000); 
  Serial.println("Hi after wake up via GPIO Button!");
  delay(2000); 
}

Answer 1

I've figured out by myself what the trouble was: just change to rtc_io ext0 and set level on 0. Then it will work fine. (Maybe this will be helpful for other users.)

Answer 2

I was able to find the solution, I've updated the code and the solution, here you go,

Prerequisites:

• BUTTON to be connected with 3.3V at at a GPIO PIN (In my case GPIO-15 for ESP32 Devkit v3)

I've added couple of extra functions:

• uart_tx_wait_idle(CONFIG_ESP_CONSOLE_UART_NUM), so that esp32 would wait until all the console are printed out, else it would cut off in the middle.
• setup proper pulldown resistor (For beginners this has a very clear explanation - https://www.youtube.com/watch?v=_8HYjjaT7BM)
• esp_sleep_enable_ext0_wakeup to listen to the port for wakeup.

#include <esp_sleep.h>
#include "esp32/rom/uart.h"
#include "driver/rtc_io.h"
void setup() {

  Serial.begin(115200);
  gpio_wakeup_enable(GPIO_NUM_15, GPIO_INTR_HIGH_LEVEL);
  esp_sleep_enable_timer_wakeup(5000000);
  rtc_gpio_pulldown_en(GPIO_NUM_15);
  rtc_gpio_pullup_dis(GPIO_NUM_15);
  Serial.println("Going to sleep now");
  uart_tx_wait_idle(CONFIG_ESP_CONSOLE_UART_NUM);
  esp_sleep_enable_ext0_wakeup(GPIO_NUM_15, 1);
  esp_light_sleep_start();
  delay(2000); 
  Serial.println("This will be printed");
}

void loop() {
      if (rtc_gpio_get_level(GPIO_NUM_15) == 1)  {
        printf("please release button\n");
        do
        {
            vTaskDelay(pdMS_TO_TICKS(10));
        } while (rtc_gpio_get_level(GPIO_NUM_15) == 1);
    }
  Serial.println("Hi after wake up!");
  Serial.println("Going to sleep now!");
  uart_tx_wait_idle(CONFIG_ESP_CONSOLE_UART_NUM);
  esp_light_sleep_start();
}

For anyone coming from RTOS background, here's my solution,

#include "driver/rtc_io.h"
#include "stdio.h"
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "esp_sleep.h"
#include "esp32/rom/uart.h"
#include "time.h"
#include "sys/time.h"
#include "esp_timer.h"

#define PIN_SWITCH 15
#define PIN_LED 2

void app_main()
{

    printf("\nSleep Program Running..\n");
    gpio_set_direction(PIN_SWITCH, GPIO_MODE_INPUT);
    gpio_wakeup_enable(PIN_SWITCH, GPIO_INTR_HIGH_LEVEL);
    rtc_gpio_pulldown_en(PIN_SWITCH);
    rtc_gpio_pullup_dis(PIN_SWITCH);
    gpio_set_direction(PIN_LED, GPIO_MODE_OUTPUT);

    esp_sleep_enable_timer_wakeup(5000000);

    while (true)
    {
        if (rtc_gpio_get_level(PIN_SWITCH) == 1)
        {
            printf("please release button\n");
            do
            {
                vTaskDelay(pdMS_TO_TICKS(10));
            } while (rtc_gpio_get_level(PIN_SWITCH) == 1);
        }
        printf("Going for a nap\n");
        uart_tx_wait_idle(CONFIG_ESP_CONSOLE_UART_NUM);
        int64_t before = esp_timer_get_time();
        gpio_set_level(PIN_LED, 0);
        esp_sleep_enable_ext0_wakeup(PIN_SWITCH, 1);
        esp_light_sleep_start();
        gpio_set_level(PIN_LED, 1);
        int64_t after = esp_timer_get_time();
        esp_sleep_wakeup_cause_t reason = esp_sleep_get_wakeup_cause();
        printf("Waked up Event %d - Sleep for %lld \n", reason, (after - before) / 1000);
        vTaskDelay(1);
    }
}