Arduino Nano ESP32 - Web Apps Web Plotter
Overview
This tutorial covers the DIYablesWebPlotterPage class from the DIYables ESP32 WebApps Library. The page renders a streaming line chart in the browser. The Arduino Nano ESP32 sketch sends data points over WebSocket; the browser appends each point to the corresponding series in real time. Up to 8 independent data series are supported simultaneously.
Watch this step-by-step video tutorial demonstrating how to use a DHT sensor with the Web Plotter app:
What This Tutorial Covers
- Configuring the plotter title, axis labels, and sample retention limit
- Sending named data points from the sketch using addDataPoint()
- Plotting multiple series simultaneously
- Replacing simulated data with real sensor readings
Hardware Preparation
Or you can buy the following kits:
| 1 | × | DIYables Sensor Kit (18 sensors/displays) |
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Additionally, some of these links are for products from our own brand, DIYables .
Additionally, some of these links are for products from our own brand, DIYables .
Steps
Follow these instructions step by step:
- If this is your first time using the Arduino Nano ESP32, refer to the tutorial on setting up the Arduino Nano ESP32 development environment.
- Connect the Arduino Nano ESP32 board to your computer using a USB cable.
- Launch the Arduino IDE on your computer.
- Select the appropriate board (e.g. Arduino Nano ESP32) and COM port.
- Navigate to the Libraries icon on the left bar of the Arduino IDE.
- Search "DIYables ESP32 WebApps", then find the DIYables ESP32 WebApps Library by DIYables
- Click Install button to install the library.
- Search for DIYables ESP32 WebApps created by DIYables and click the Install button.
1
void setup() {
- You will be asked for installing some other library dependencies
- Click Install All button to install all library dependencies.
- On Arduino IDE, Go to File Examples DIYables ESP32 WebApps WebPlotter example, or copy the above code and paste it to the editor of Arduino IDE
/*
* DIYables WebApp Library - Web Plotter Example
*
* This example demonstrates the Web Plotter feature:
* - Real-time data visualization
* - Multiple data series support
* - Auto-scaling Y-axis
* - Responsive web interface
* - WebSocket communication for instant updates
*
* Hardware: ESP32 Boards
*
* Setup:
* 1. Update WiFi credentials below
* 2. Upload the sketch to your Arduino
* 3. Open Serial Monitor to see the IP address
* 4. Navigate to http://[IP_ADDRESS]/webplotter
*/
#include <DIYables_ESP32_Platform.h>
#include <DIYablesWebApps.h>
// WiFi credentials - UPDATE THESE WITH YOUR NETWORK
const char WIFI_SSID[] = "YOUR_WIFI_SSID";
const char WIFI_PASSWORD[] = "YOUR_WIFI_PASSWORD";
// Create WebApp server and page instances
ESP32ServerFactory serverFactory;
DIYablesWebAppServer webAppsServer(serverFactory, 80, 81);
DIYablesHomePage homePage;
DIYablesWebPlotterPage webPlotterPage;
// Simulation variables
unsigned long lastDataTime = 0;
const unsigned long DATA_INTERVAL = 1000; // Send data every 1000ms
float timeCounter = 0;
void setup() {
Serial.begin(9600);
delay(1000);
// TODO: Initialize your hardware pins and sensors here
Serial.println("DIYables ESP32 WebApp - Web Plotter Example");
// Add home and web plotter pages
webAppsServer.addApp(&homePage);
webAppsServer.addApp(&webPlotterPage);
// Optional: Add 404 page for better user experience
webAppsServer.setNotFoundPage(DIYablesNotFoundPage());
// Configure the plotter
webPlotterPage.setPlotTitle("Real-time Data Plotter");
webPlotterPage.setAxisLabels("Time (s)", "Values");
webPlotterPage.enableAutoScale(true);
webPlotterPage.setMaxSamples(50);
// Start the WebApp server
if (!webAppsServer.begin(WIFI_SSID, WIFI_PASSWORD)) {
while (1) {
Serial.println("Failed to start WebApp server!");
delay(1000);
}
}
// Set up callbacks
webPlotterPage.onPlotterDataRequest([]() {
Serial.println("Web client requested data");
sendSensorData();
});
Serial.println("\nWebPlotter is ready!");
Serial.println("Usage Instructions:");
Serial.println("1. Connect to the WiFi network");
Serial.println("2. Open your web browser");
Serial.println("3. Navigate to the Arduino's IP address");
Serial.println("4. Click on 'Web Plotter' to view real-time data");
Serial.println("\nGenerating simulated sensor data...");
}
void loop() {
// Handle web server and WebSocket connections
webAppsServer.loop();
// Send sensor data at regular intervals
if (millis() - lastDataTime >= DATA_INTERVAL) {
lastDataTime = millis();
sendSensorData();
timeCounter += DATA_INTERVAL / 1000.0; // Convert to seconds
}
}
void sendSensorData() {
// Generate simulated sensor data
// In a real application, replace these with actual sensor readings
// Simulated temperature sensor (sine wave with noise)
float temperature = 25.0 + 5.0 * sin(timeCounter * 0.5) + random(-100, 100) / 100.0;
// Simulated humidity sensor (cosine wave)
float humidity = 50.0 + 20.0 * cos(timeCounter * 0.3);
// Simulated light sensor (triangle wave)
float light = 512.0 + 300.0 * (2.0 * abs(fmod(timeCounter * 0.2, 2.0) - 1.0) - 1.0);
// Simulated analog pin reading
float analogValue = analogRead(A0);
// Send data using different methods:
// Method 1: Send individual values (uncomment to use)
// webPlotterPage.sendPlotData(temperature);
// Method 2: Send multiple values at once
webPlotterPage.sendPlotData(temperature, humidity, light / 10.0, analogValue / 100.0);
// Method 3: Send array of values (alternative approach)
// float values[] = {temperature, humidity, light / 10.0, analogValue / 100.0};
// webPlotterPage.sendPlotData(values, 4);
// Method 4: Send raw data string (for custom formatting)
// String dataLine = String(temperature, 2) + " " + String(humidity, 1) + " " + String(light / 10.0, 1);
// webPlotterPage.sendPlotData(dataLine);
// Print to Serial Monitor in Serial Plotter compatible format
// Format: Temperature Humidity Light Analog (tab-separated for Serial Plotter)
Serial.print(temperature, 1);
Serial.print("\t");
Serial.print(humidity, 1);
Serial.print("\t");
Serial.print(light / 10.0, 1);
Serial.print("\t");
Serial.println(analogValue / 100.0, 2);
}
- Update the WiFi credentials in the sketch:
const char WIFI_SSID[] = "YOUR_WIFI_NETWORK";
const char WIFI_PASSWORD[] = "YOUR_WIFI_PASSWORD";
- Click Upload button on Arduino IDE to upload code to Arduino Nano ESP32
- Open the Serial Monitor
- The Serial Monitor output should resemble the following:
8
Serial.println("Hello World!");
Message (Enter to send message to 'Arduino Nano ESP32' on 'COM15')
New Line
9600 baud
DIYables WebApp - Web Plotter Example
INFO: Added app /
INFO: Added app /web-plotter
DIYables WebApp Library
Platform: Arduino Nano ESP32
Network connected!
IP address: 192.168.0.2
HTTP server started on port 80
Configuring WebSocket server callbacks...
WebSocket server started on port 81
WebSocket URL: ws://192.168.0.2:81
WebSocket server started on port 81
==========================================
DIYables WebApp Ready!
==========================================
Web Interface: http://192.168.0.2
WebSocket: ws://192.168.0.2:81
Available Applications:
Home Page: http://192.168.0.2/
Web Plotter: http://192.168.0.2/web-plotter
==========================================
- If nothing appears, press the reset button on the board.
- Enter the IP address from the Serial Monitor into a browser on the same network.
- Example: http://192.168.0.2
- The home page shows a card for the plotter application:
- Select the Web Plotter card to open the chart page:
- The page is also directly accessible at http://192.168.0.2/web-plotter.
- The chart begins updating as the sketch sends simulated data. Each series is drawn in a distinct color.
Plotter Configuration
Set the chart title, axis labels, auto-scale behavior, and maximum retained samples before starting the server:
webPlotterPage.setPlotTitle("Sensor Data");
webPlotterPage.setAxisLabels("Time (s)", "Value");
webPlotterPage.enableAutoScale(true);
webPlotterPage.setMaxSamples(100); // Keep last 100 points per series
Sending Data Points
Each data point specifies a series name, X value, and Y value. The series is created automatically on first use:
// Single series
webPlotterPage.addDataPoint("temperature", elapsedSeconds, sensorValue);
// Multiple series in the same update cycle
webPlotterPage.addDataPoint("temperature", t, tempValue);
webPlotterPage.addDataPoint("humidity", t, humValue);
webPlotterPage.addDataPoint("pressure", t, pressValue);
Reading from Real Sensors
Replace the simulated values in the example with actual sensor readings:
Single Sensor
float temperature = analogRead(A0) * (5.0 / 1023.0) * 100.0; // LM35
webPlotterPage.addDataPoint("LM35", millis() / 1000.0, temperature);
Multiple Sensors
float temp = readTemperature();
float humid = readHumidity();
webPlotterPage.addDataPoint("Temp", millis() / 1000.0, temp);
webPlotterPage.addDataPoint("Humid", millis() / 1000.0, humid);
Limit the send rate to avoid overwhelming the WebSocket connection. A 500 ms to 1000 ms interval is suitable for most sensor applications.
Troubleshooting
Chart does not update
- Confirm webAppsServer.loop() runs on every loop() iteration
- Add Serial.println() before addDataPoint() to verify the code path executes
- Reload the browser page and check the WebSocket connection indicator
Chart shows flat lines or wrong values
- Verify the sensor read and scaling formula
- Print the value to the Serial Monitor alongside sending it to the plotter
Too many data points slow the browser
- Lower setMaxSamples() to reduce the points retained per series
- Increase the delay between data sends
Board not reachable
- Confirm the IP address from the Serial Monitor
- Ensure the browser device is on the same 2.4 GHz network as the board