Implement ESP32 Deep Sleep with RTC Memory for Battery-Powered IoT Sensors

Implementing ESP32 Deep Sleep with RTC Memory Retention for Sensor Data Logging in Battery-Powered IoT Devices

In this tutorial, we will implement deep sleep functionality on the ESP32 while retaining sensor data in RTC (Real Time Clock) memory. This is particularly useful for battery-powered IoT devices that need to minimize power consumption while logging sensor data.

Prerequisites

• Basic understanding of Arduino programming
• ESP32 development board
• Arduino IDE installed on your computer
• USB cable for connecting the ESP32 to your computer
• Some sensors (e.g., temperature, humidity) for data logging

Parts/Tools

• ESP32 Development Board
• Jumper wires (if necessary)
• Sensor(s) of your choice (e.g., DHT11 for temperature/humidity)
• Arduino IDE

Steps

1. Set Up Your Arduino IDE
   1. Open the Arduino IDE.
   2. Go to File > Preferences.
   3. In the Additional Board Manager URLs field, add this link:

      https://dl.espressif.com/dl/package_esp32_index.json

   4. Go to Tools > Board > Boards Manager, search for “ESP32,” and install the package.
2. Connect Your Sensor
   1. Connect the sensor to the ESP32 according to its datasheet.
   2. For example, for a DHT11 sensor, connect the data pin to GPIO 23.
3. Write the Code
   1. Open a new sketch in Arduino IDE and include the necessary libraries:

   #include "DHT.h"
   #define DHTPIN 23
   #define DHTTYPE DHT11
   DHT dht(DHTPIN, DHTTYPE);

   2. Initialize the sensor and RTC memory:

   
   void setup() {
       Serial.begin(115200);
       dht.begin();
       Serial.println("Initializing...");
   }

   3. Read sensor data and store it in RTC memory:

   
   void logSensorData() {
       float humidity = dht.readHumidity();
       float temperature = dht.readTemperature();
       // Store data in RTC memory
       RTC_DATA_ATTR float storedHumidity;
       RTC_DATA_ATTR float storedTemperature;
       storedHumidity = humidity;
       storedTemperature = temperature;
   }

   4. Implement the deep sleep functionality:

   
   void enterDeepSleep() {
       Serial.println("Entering Deep Sleep...");
       esp_sleep_enable_timer_wakeup(60000000); // Sleep for 60 seconds
       esp_deep_sleep_start();
   }

   5. Combine everything in the loop:

   
   void loop() {
       logSensorData();
       enterDeepSleep();
   }

4. Upload the Code
   1. Select the correct board and port under Tools.
   2. Click on the upload button to upload your code to the ESP32.

Troubleshooting

• Device Not Connecting: Ensure the correct board and COM port are selected in the Arduino IDE.
• No Data from Sensor: Check your wiring and ensure the sensor is powered and connected correctly.
• Code Not Uploading: Try pressing the reset button on the ESP32 just before uploading.
• Deep Sleep Not Working: Verify the deep sleep time configuration and ensure no other operations are preventing sleep.

Conclusion

By following this tutorial, you have successfully implemented deep sleep functionality on the ESP32 while retaining sensor data in RTC memory. This approach is ideal for battery-powered IoT devices, allowing them to log data efficiently while minimizing power consumption. Experiment with different sensors and deep sleep durations to suit your application’s needs.