How to Read Data from ThingSpeak using ESP32: Complete Guide

Why Use ESP32 with ThingSpeak for IoT Projects

The ESP32 microcontroller is perfectly suited for an ESP32 project with ThingSpeak integration due to its built-in Wi-Fi capabilities, dual-core processing power, and extensive memory resources.

Unlike the SP8266, the ESP32 offers superior processing capabilities and supports both Wi-Fi and Bluetooth connectivity, making it versatile for complex IoT applications.

The combination enables seamless data transmission to cloud platforms, real-time monitoring capabilities, and cost-effective solutions for weather stations, sensor networks, and automation systems.

Hardware and Software Requirements

Hardware Components

• ESP32 development board (ESP32 DevKit or similar) 
• USB cable for programming and power 
• Stable power supply (optional for standalone operation) 
• Sensors (optional, for actual data collection)

Software Requirements

• Arduino IDE with ESP32 board support 
• WiFi library (built-in ESP32 library) 
• HTTPClient library for HTTP requests 
• ArduinoJson library for parsing JSON responses 
• ThingSpeak library (optional, for simplified integration)

Setting Up a ThingSpeak Channel for Data Storage

Creating a ThingSpeak channel is essential for reading data from ThingSpeak using ESP32. First, create a free account at thingspeak.com and navigate to the "Channels" section.

Create a new channel by specifying field names (Field1, Field2, etc.) that correspond to your data types. After creation, locate your Channel ID in the channel URL and copy the Read API Key from the "API Keys" tab.

These credentials are crucial for authentication when your ESP32 makes data requests to the ThingSpeak servers.

Connecting ESP32 to Wi-Fi Network

The ESP32 WiFi connection setup is fundamental for cloud communication. The process involves initializing the WiFi library, connecting to your network using SSID and password credentials, and establishing a stable connection before attempting data operations. Here's the essential setup code:

#include  <WiFi.h>
 
const char* ssid = "YOUR_WIFI_SSID"; 
const char* password = "YOUR_WIFI_PASSWORD"; 
 
void setup() { 
  Serial.begin(115200); 
  WiFi.begin(ssid, password); 
   
  while (WiFi.status() != WL_CONNECTED) { 
    delay(500); 
    Serial.print("."); 
  } 
   
  Serial.println("WiFi connected!"); 
}

The connection status should be verified before attempting any HTTP operations to ensure reliable data transmission.

Steps to Read Data from ThingSpeak using ESP32

Required Libraries

• Install the necessary libraries in your Arduino IDE : 
• WiFi: Built-in ESP32 library for wireless connectivity 
• HTTPClient: For making HTTP requests to ThingSpeak API 
• ArduinoJson: For parsing JSON responses from ThingSpeak 
• ThingSpeak: Official library for easier ThingSpeak integration

Installing Libraries

1. Open Arduino IDE 
2. Go to Sketch > Include Library > Manage Libraries 
3. Search and install "ThingSpeak" by MathWorks 
4. Search and install "ArduinoJson" by Benoit Blanchon

ThingSpeak Channel Setup

Get Your Channel Information

1. Log into your ThingSpeak account at thingspeak.com 
2. Navigate to your channel or create a new one 
3. Note down your Channel ID (visible in the channel URL) 
4. Go to the API Keys tab and copy your Read API Key

Hardware Setup

Connect your ESP32 to your computer via USB cable. No additional hardware is required for basic data reading but ensure your ESP32 has stable power supply.

Code Implementation

Basic HTTP GET Method

Here's the complete code to read data from ThingSpeak using HTTP GET requests:

#include <WiFi.h>
#include <HTTPClient.h> 
#include <ArduinoJson.h> 
 
// WiFi credentials 
const char* ssid = "YOUR_WIFI_SSID"; 
const char* password = "YOUR_WIFI_PASSWORD"; 
 
// ThingSpeak settings 
unsigned long channelID = YOUR_CHANNEL_ID; 
const char* readAPIKey = "YOUR_READ_API_KEY"; 
const char* server = "api.thingspeak.com"; 
 
// Variables to store sensor data 
float field1Value = 0; 
float field2Value = 0; 
 
void setup() { 

  Serial.begin(115200); 
   
  // Connect to WiFi 
  WiFi.begin(ssid, password); 
  Serial.print("Connecting to WiFi"); 
   
  while (WiFi.status() != WL_CONNECTED) { 
    delay(500); 
    Serial.print("."); 
  } 
   
  Serial.println(); 
  Serial.println("WiFi connected!"); 
  Serial.print("IP address: "); 
  Serial.println(WiFi.localIP()); 
} 
 
void loop() { 
  if (WiFi.status() == WL_CONNECTED) { 
    readThingSpeakData(); 
    delay(20000); // Read data every 20 seconds 
  } 
} 
 
void readThingSpeakData() { 
  HTTPClient http; 
   
  // Construct the URL for reading data 
  String url = "http://api.thingspeak.com/channels/" + String(channelID) +  
               "/feeds.json?api_key=" + String(readAPIKey) + "&results=1"; 
   
  http.begin(url); 
  int httpResponseCode = http.GET(); 
   
  if (httpResponseCode > 0) { 
    String payload = http.getString(); 
    Serial.println("HTTP Response: " + String(httpResponseCode)); 
    Serial.println("Payload: " + payload); 
     
    // Parse JSON response 
    parseJSON(payload); 
  } else { 
    Serial.println("Error in HTTP request: " + String(httpResponseCode)); 
  } 
   
  http.end(); 
} 
 
void parseJSON(String jsonString) { 
  DynamicJsonDocument doc(2048); 
  deserializeJson(doc, jsonString); 
   
  // Extract channel information 
  int channelId = doc["channel"]["id"]; 
  String channelName = doc["channel"]["name"]; 
   
  Serial.println("Channel ID: " + String(channelId)); 
  Serial.println("Channel Name: " + channelName); 
   
  // Extract feed data (most recent entry) 
  if (doc["feeds"].size() > 0) { 
    JsonObject feed = doc["feeds"][0]; 
     
    String createdAt = feed["created_at"]; 
    field1Value = feed["field1"].as<float>(); 
    field2Value = feed["field2"].as<float>(); 
     
    Serial.println("Latest Entry:"); 
    Serial.println("Timestamp: " + createdAt); 
    Serial.println("Field 1: " + String(field1Value)); 
    Serial.println("Field 2: " + String(field2Value)); 
  } 
   
  Serial.println("------------------------"); 
}
 

Using ThingSpeak Library Method

Alternative approach using the official ThingSpeak library:

#include <WiFi.h> 
#include "ThingSpeak.h" 
 
const char* ssid = "YOUR_WIFI_SSID"; 
const char* password = "YOUR_WIFI_PASSWORD"; 
 
WiFiClient client; 
 
unsigned long channelID = YOUR_CHANNEL_ID; 
const char* readAPIKey = "YOUR_READ_API_KEY"; 
 
void setup() { 
  Serial.begin(115200); 
  WiFi.mode(WIFI_STA); 
   
  WiFi.begin(ssid, password); 
  while (WiFi.status() != WL_CONNECTED) { 
    delay(500); 
    Serial.print("."); 
  } 
   
  Serial.println("WiFi connected!"); 
  ThingSpeak.begin(client); 
} 
 
void loop() { 
  // Read specific field value 
  float field1 = ThingSpeak.readFloatField(channelID, 1, readAPIKey); 
  int statusCode = ThingSpeak.getLastReadStatus(); 
   
  if (statusCode == 200) { 
    Serial.println("Field 1: " + String(field1)); 
  } else { 
    Serial.println("Problem reading channel. HTTP error code " + String(statusCode)); 
  } 
   
  delay(20000); // ThingSpeak allows updates every 15 seconds 
}

Configuration Steps

Update Code Parameters

Replace the following placeholders in your code: 

• YOUR_WIFI_SSID: Your WiFi network name 
• YOUR_WIFI_PASSWORD: Your WiFi password 
• YOUR_CHANNEL_ID: Your ThingSpeak channel ID number 
• YOUR_READ_API_KEY: Your channel's Read API Key

URL Structure Understanding

ThingSpeak uses RESTful API endpoints for data retrieval:

• Basic format: https://api.thingspeak.com/channels/CHANNEL_ID/feeds.json 
• With API key: ?api_key=READ_API_KEY 
• Limit results: &results=NUMBER_OF_ENTRIES 
• Specific field: /fields/FIELD_NUMBER.json

Data Rate Limits

ThingSpeak has rate limits for data retrieval: 

• Maximum 8,000 requests per day for free accounts 
• Recommended minimum interval: 15-20 seconds between requests 
• Use results parameter to limit returned data and reduce bandwidth

Advanced Features

Reading Multiple Fields

To read specific fields individually:

// Read multiple fields separately 
float temperature = ThingSpeak.readFloatField(channelID, 1, readAPIKey); 
float humidity = ThingSpeak.readFloatField(channelID, 2, readAPIKey); 
float pressure = ThingSpeak.readFloatField(channelID, 3, readAPIKey);

Reading Historical Data

Modify the URL to get historical entries:

String url = "http://api.thingspeak.com/channels/" + String(channelID) +  
             "/feeds.json?api_key=" + String(readAPIKey) + "&results=10";

This implementation provides a complete foundation for reading data from ThingSpeak using ESP32, with both HTTP client and ThingSpeak library approaches for different use cases.

Conclusion

Reading data from ThingSpeak using ESP32 provides a powerful and cost-effective solution for IoT monitoring applications.

The ESP32's built-in Wi-Fi capabilities combined with ThingSpeak's cloud platform enable remote data access from anywhere in the world.

This integration offers real-time visualization, data analysis, and reliable communication for weather stations, sensor networks, and automation projects.

With proper implementation of rate limiting and error handling, the ESP32-ThingSpeak combination delivers a robust foundation for scalable IoT data retrieval systems.