ESP8266 - Web Plotter
This tutorial instructs you on how to build a web-based plotter resembling the Serial Plotter found in the Arduino IDE. This setup allows you to conveniently monitor real-time data from an ESP8266 using a web browser on either your smartphone or PC. It will visualize the data in a graphical format similar to what you observe in the Serial Plotter of the Arduino IDE.
Hardware Preparation
| 1 | × | ESP8266 NodeMCU | |
| 1 | × | USB Cable Type-C | |
| 1 | × | (Recommended) Screw Terminal Expansion Board for ESP8266 | |
| 1 | × | (Recommended) Power Splitter For ESP8266 Type-C |
Or you can buy the following sensor kits:
| 1 | × | DIYables Sensor Kit (30 sensors/displays) | |
| 1 | × | DIYables Sensor Kit (18 sensors/displays) |
Disclosure: Some of the links provided in this section are Amazon affiliate links. We may receive a commission for any purchases made through these links at no additional cost to you.
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.
How Web Plotter Works
- The ESP8266 code creates both a web server and WebSocket server.
- When a user accesses the webpage hosted on the ESP8266 board via a web browser, the ESP8266's web server sends back the web content (HTML, CSS, JavaScript) to the browser.
- The JavaScript code running in the web browser renders a graph resembling the Serial Plotter.
- Upon clicking the connect button on the webpage, the JavaScript code establishes a WebSocket connection to the WebSocket server running on the ESP8266 board.
- The ESP8266 sends data over the WebSocket connection to the web browser in a format similar to that used by the Serial Plotter (details provided in the next section).
- The JavaScript code in the web browser receives the data and plots it on the graph.
The data format that ESP8266 sends to web plotter
To plot multiple variables, we need to separate variables from each other by “\t” or " " character. The last value MUST be terminated by “\r\n” characters.
In detail:
- The first variable
plotter.broadcastTXT(line_1);
- The middle variables
plotter.broadcastTXT("\t"); // a tab '\t' or space ' ' character is printed between the two values.
plotter.broadcastTXT(line_2);
plotter.broadcastTXT("\t"); // a tab '\t' or space ' ' character is printed between the two values.
plotter.broadcastTXT(line_3);
- The last variable
plotter.broadcastTXT("\t"); // a tab '\t' or space ' ' character is printed between the two values.
plotter.broadcastTXT(line_4);
plotter.broadcastTXT("\r\n"); // the last value is terminated by a carriage return and a newline characters.
For more detail, please refer to ESP8266 - Serial Plotter tutorial
ESP8266 Code - Web Plotter
The webpage's content (HTML, CSS, JavaScript) are stored separately on an index.h file. So, we will have two code files on Arduino IDE:
- An .ino file that is ESP8266 code, which creates a web sever and WebSocket server
- An .h file, which contains the webpage's content.
Detailed Instructions
To get started with ESP8266 on Arduino IDE, follow these steps:
- Check out the how to setup environment for ESP8266 on Arduino IDE tutorial if this is your first time using ESP8266.
- Connect the ESP8266 board to your computer using a USB cable.
- Open Arduino IDE on your computer.
- Choose the correct ESP8266 board, such as (e.g. NodeMCU 1.0 (ESP-12E Module)), and its respective COM port.
- Open the Library Manager by clicking on the Library Manager icon on the left navigation bar of Arduino IDE.
- Search “WebSockets”, then find the WebSockets created by Markus Sattler.
- Click Install button to install WebSockets library.
- On Arduino IDE, create new sketch, Give it a name, for example, newbiely.com.ino
- Copy the below code and open with Arduino IDE
/*
* This ESP8266 NodeMCU code was developed by newbiely.com
*
* This ESP8266 NodeMCU code is made available for public use without any restriction
*
* For comprehensive instructions and wiring diagrams, please visit:
* https://newbiely.com/tutorials/esp8266/esp8266-web-plotter
*/
#include <ESP8266WiFi.h>
#include <ESP8266WebServer.h>
#include <WebSocketsServer.h>
#include "index.h" // contains HTML, JavaScript and CSS
const char* ssid = "YOUR_WIFI_SSID"; // CHANGE IT TO MATCH YOUR OWN NETWORK CREDENTIALS
const char* password = "YOUR_WIFI_PASSWORD"; // CHANGE IT TO MATCH YOUR OWN NETWORK CREDENTIALS
ESP8266WebServer server(80); // Web server on port 80
WebSocketsServer plotter = WebSocketsServer(81); // WebSocket server on port 81
int last_update = 0;
void setup() {
Serial.begin(9600);
delay(500);
// Connect to Wi-Fi
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
delay(1000);
Serial.println("Connecting to WiFi...");
}
Serial.println("Connected to WiFi");
// Initialize WebSocket server
plotter.begin();
// Serve a basic HTML page with JavaScript to create the WebSocket connection
server.on("/", HTTP_GET, []() {
Serial.println("Web Server: received a web page request");
String html = HTML_CONTENT; // Use the HTML content from the index.h file
server.send(200, "text/html", html);
});
server.begin();
Serial.print("ESP8266 Web Server's IP address: ");
Serial.println(WiFi.localIP());
}
void loop() {
// Handle client requests
server.handleClient();
// Handle WebSocket events
plotter.loop();
if (millis() - last_update > 500) {
last_update = millis();
String line_1 = String(random(0, 100));
String line_2 = String(random(0, 100));
String line_3 = String(random(0, 100));
String line_4 = String(random(0, 100));
// TO SERIAL PLOTTER
Serial.print(line_1);
Serial.print("\t"); // A tab character ('\t') or a space (' ') is printed between the two values.
Serial.print(line_2);
Serial.print("\t"); // A tab character ('\t') or a space (' ') is printed between the two values.
Serial.print(line_3);
Serial.print("\t"); // A tab character ('\t') or a space (' ') is printed between the two values.
Serial.println(line_4); // The last value is terminated by a carriage return ('\r') and a newline ('\n') character.
// TO WEB PLOTTER
plotter.broadcastTXT(line_1);
plotter.broadcastTXT("\t"); // A tab character ('\t') or a space (' ') is printed between the two values.
plotter.broadcastTXT(line_2);
plotter.broadcastTXT("\t"); // A tab character ('\t') or a space (' ') is printed between the two values.
plotter.broadcastTXT(line_3);
plotter.broadcastTXT("\t"); // A tab character ('\t') or a space (' ') is printed between the two values.
plotter.broadcastTXT(line_4);
plotter.broadcastTXT("\r\n"); // The last value is terminated by a carriage return ('\r') and a newline ('\n') character.
}
}
- Modify the WiFi information (SSID and password) in the code to match your own network credentials.
- Create the index.h file On Arduino IDE by:
- Either click on the button just below the serial monitor icon and choose New Tab, or use Ctrl+Shift+N keys.
- Give the file's name index.h and click OK button
- Copy the below code and paste it to the index.h.
- Now you have the code in two files: newbiely.com.ino and index.h
- Click Upload button on Arduino IDE to upload code to ESP8266.
- Open the Serial Monitor
- Check out the result on Serial Monitor.
- Take note of the IP address displayed, and enter this address into the address bar of a web browser on your smartphone or PC.
- You will see the webpage it as below:
- Click the CONNECT button to connect the webpage to ESP8266 via WebSocket.
- You will see the plotter plots data as the below image.
- You can open the Serial Plotter on Arduino IDE to compare with the Web Plotter on the web browser.
- If you modify the HTML content in the index.h and does not touch anything in newbiely.com.ino file, when you compile and upload code to ESP8266, Arduino IDE will not update the HTML content.
- To make Arduino IDE update the HTML content in this case, make a change in the newbiely.com.ino file (e.g. adding empty line, add a comment....)
/*
* This ESP8266 NodeMCU code was developed by newbiely.com
*
* This ESP8266 NodeMCU code is made available for public use without any restriction
*
* For comprehensive instructions and wiring diagrams, please visit:
* https://newbiely.com/tutorials/esp8266/esp8266-web-plotter
*/
const char *HTML_CONTENT = R"=====(
<!DOCTYPE html>
<html>
<head>
<title>ESP8266 - Web Plotter</title>
<meta name="viewport" content="width=device-width, initial-scale=0.7">
<style>
body {text-align: center; height: 750px; }
h1 {font-weight: bold; font-size: 20pt; padding-bottom: 5px; color: navy; }
h2 {font-weight: bold; font-size: 15pt; padding-bottom: 5px; }
button {font-weight: bold; font-size: 15pt; }
#footer {width: 100%; margin: 0px; padding: 0px 0px 10px 0px; bottom: 0px; }
.sub-footer {margin: 0 auto; position: relative; width:400px; }
.sub-footer a {position: absolute; font-size: 10pt; top: 3px; }
</style>
<script>
var COLOR_BACKGROUND = "#FFFFFF";
var COLOR_TEXT = "#000000";
var COLOR_BOUND = "#000000";
var COLOR_GRIDLINE = "#F0F0F0";
var COLOR_LINE = ["#0000FF", "#FF0000", "#009900", "#FF9900", "#CC00CC", "#666666", "#00CCFF", "#000000"];
var LEGEND_WIDTH = 10;
var X_TITLE_HEIGHT = 40;
var Y_TITLE_WIDTH = 40;
var X_VALUE_HEIGHT = 40;
var Y_VALUE_WIDTH = 50;
var PLOTTER_PADDING_TOP = 30;
var PLOTTER_PADDING_RIGHT = 30;
var X_GRIDLINE_NUM = 5;
var Y_GRIDLINE_NUM = 4;
var WSP_WIDTH = 400;
var WSP_HEIGHT = 200;
var MAX_SAMPLE = 50; // in sample
var X_MIN = 0;
var X_MAX = MAX_SAMPLE;
var Y_MIN = -5;
var Y_MAX = 5;
var X_TITLE = "X";
var Y_TITLE = "Y";
var plotter_width;
var plotter_height;
var plotter_pivot_x;
var plotter_pivot_y;
var sample_count = 0;
var buffer = "";
var data = [];
var webSocket;
var canvas;
var ctx;
function plotter_init(){
canvas = document.getElementById("graph");
canvas.style.backgroundColor = COLOR_BACKGROUND;
ctx = canvas.getContext("2d");
canvas_resize();
setInterval(update_plotter, 1000 / 60);
}
function plotter_to_esp8266(){
if(webSocket == null){
webSocket = new WebSocket("ws://" + window.location.host + ":81");
document.getElementById("ws_state").innerHTML = "CONNECTING";
webSocket.onopen = ws_onopen;
webSocket.onclose = ws_onclose;
webSocket.onmessage = ws_onmessage;
webSocket.binaryType = "arraybuffer";
}
else
webSocket.close();
}
function ws_onopen(){
document.getElementById("ws_state").innerHTML = "<span style='color: blue'>CONNECTED</span>";
document.getElementById("btn_connect").innerHTML = "Disconnect";
}
function ws_onclose(){
document.getElementById("ws_state").innerHTML = "<span style='color: gray'>CLOSED</span>";
document.getElementById("btn_connect").innerHTML = "Connect";
webSocket.onopen = null;
webSocket.onclose = null;
webSocket.onmessage = null;
webSocket = null;
}
function ws_onmessage(e_msg){
e_msg = e_msg || window.event; // MessageEvent
console.log(e_msg.data);
buffer += e_msg.data;
buffer = buffer.replace(/\r\n/g, "\n");
buffer = buffer.replace(/\r/g, "\n");
while(buffer.indexOf("\n") == 0)
buffer = buffer.substr(1);
if(buffer.indexOf("\n") <= 0)
return;
var pos = buffer.lastIndexOf("\n");
var str = buffer.substr(0, pos);
var new_sample_arr = str.split("\n");
buffer = buffer.substr(pos + 1);
for(var si = 0; si < new_sample_arr.length; si++) {
var str = new_sample_arr[si];
var arr = [];
if(str.indexOf("\t") > 0)
arr = str.split("\t");
else
arr = str.split(" ");
for(var i = 0; i < arr.length; i++){
var value = parseFloat(arr[i]);
if(isNaN(value))
continue;
if(i >= data.length) {
var new_line = [value];
data.push(new_line); // new line
}
else
data[i].push(value);
}
sample_count++;
}
for(var line = 0; line < data.length; line++){
while(data[line].length > MAX_SAMPLE)
data[line].splice(0, 1);
}
auto_scale();
}
function map(x, in_min, in_max, out_min, out_max){
return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
}
function get_random_color(){
var letters = '0123456789ABCDEF';
var _color = '#';
for (var i = 0; i < 6; i++)
_color += letters[Math.floor(Math.random() * 16)];
return _color;
}
function update_plotter(){
if(sample_count <= MAX_SAMPLE)
X_MAX = sample_count;
else
X_MAX = 50;
ctx.clearRect(0, 0, WSP_WIDTH, WSP_HEIGHT);
ctx.save();
ctx.translate(plotter_pivot_x, plotter_pivot_y);
ctx.font = "bold 20px Arial";
ctx.textBaseline = "middle";
ctx.textAlign = "center";
ctx.fillStyle = COLOR_TEXT;
// draw X axis title
if(X_TITLE != "")
ctx.fillText(X_TITLE, plotter_width / 2, X_VALUE_HEIGHT + X_TITLE_HEIGHT / 2);
// draw Y axis title
if(Y_TITLE != ""){
ctx.rotate(-90 * Math.PI / 180);
ctx.fillText(Y_TITLE, plotter_height / 2, -Y_VALUE_WIDTH - Y_TITLE_WIDTH / 2);
ctx.rotate(90 * Math.PI / 180);
}
ctx.font = "16px Arial";
ctx.textAlign = "right";
ctx.strokeStyle = COLOR_BOUND;
for(var i = 0; i <= Y_GRIDLINE_NUM; i++){
var y_gridline_px = -map(i, 0, Y_GRIDLINE_NUM, 0, plotter_height);
y_gridline_px = Math.round(y_gridline_px) + 0.5;
ctx.beginPath();
ctx.moveTo(0, y_gridline_px);
ctx.lineTo(plotter_width, y_gridline_px);
ctx.stroke();
ctx.strokeStyle = COLOR_BOUND;
ctx.beginPath();
ctx.moveTo(-7 , y_gridline_px);
ctx.lineTo(4, y_gridline_px);
ctx.stroke();
var y_gridline_value = map(i, 0, Y_GRIDLINE_NUM, Y_MIN, Y_MAX);
y_gridline_value = y_gridline_value.toFixed(1);
ctx.fillText(y_gridline_value + "", -15, y_gridline_px);
ctx.strokeStyle = COLOR_GRIDLINE;
}
ctx.strokeStyle = COLOR_BOUND;
ctx.textAlign = "center";
ctx.beginPath();
ctx.moveTo(0.5, y_gridline_px - 7);
ctx.lineTo(0.5, y_gridline_px + 4);
ctx.stroke();
for(var i = 0; i <= X_GRIDLINE_NUM; i++){
var x_gridline_px = map(i, 0, X_GRIDLINE_NUM, 0, plotter_width);
x_gridline_px = Math.round(x_gridline_px) + 0.5;
ctx.beginPath();
ctx.moveTo(x_gridline_px, 0);
ctx.lineTo(x_gridline_px, -plotter_height);
ctx.stroke();
ctx.strokeStyle = COLOR_BOUND;
ctx.beginPath();
ctx.moveTo(x_gridline_px, 7);
ctx.lineTo(x_gridline_px, -4);
ctx.stroke();
var x_gridline_value;
if(sample_count <= MAX_SAMPLE)
x_gridline_value = map(i, 0, X_GRIDLINE_NUM, X_MIN, X_MAX);
else
x_gridline_value = map(i, 0, X_GRIDLINE_NUM, sample_count - MAX_SAMPLE, sample_count);;
ctx.fillText(x_gridline_value.toString(), x_gridline_px, X_VALUE_HEIGHT / 2 + 5);
ctx.strokeStyle = COLOR_GRIDLINE;
}
var line_num = data.length;
for(var line = 0; line < line_num; line++){
// draw graph
var sample_num = data[line].length;
if(sample_num >= 2){
var y_value = data[line][0];
var x_px = 0;
var y_px = -map(y_value, Y_MIN, Y_MAX, 0, plotter_height);
if(line == COLOR_LINE.length)
COLOR_LINE.push(get_random_color());
ctx.strokeStyle = COLOR_LINE[line];
ctx.beginPath();
ctx.moveTo(x_px, y_px);
for(var i = 0; i < sample_num; i++){
y_value = data[line][i];
x_px = map(i, X_MIN, X_MAX -1, 0, plotter_width);
y_px = -map(y_value, Y_MIN, Y_MAX, 0, plotter_height);
ctx.lineTo(x_px, y_px);
}
ctx.stroke();
}
// draw legend
var x = plotter_width - (line_num - line) * LEGEND_WIDTH - (line_num - line - 1) * LEGEND_WIDTH / 2;
var y = -plotter_height - PLOTTER_PADDING_TOP / 2 - LEGEND_WIDTH / 2;
ctx.fillStyle = COLOR_LINE[line];
ctx.beginPath();
ctx.rect(x, y, LEGEND_WIDTH, LEGEND_WIDTH);
ctx.fill();
}
ctx.restore();
}
function canvas_resize(){
canvas.width = 0; // to avoid wrong screen size
canvas.height = 0;
document.getElementById('footer').style.position = "fixed";
var width = window.innerWidth - 20;
var height = window.innerHeight - 20;
WSP_WIDTH = width;
WSP_HEIGHT = height - document.getElementById('header').offsetHeight - document.getElementById('footer').offsetHeight;
canvas.width = WSP_WIDTH;
canvas.height = WSP_HEIGHT;
ctx.font = "16px Arial";
var y_min_text_size = ctx.measureText(Y_MIN.toFixed(1) + "").width;
var y_max_text_size = ctx.measureText(Y_MAX.toFixed(1) + "").width;
Y_VALUE_WIDTH = Math.round(Math.max(y_min_text_size, y_max_text_size)) + 15;
plotter_width = WSP_WIDTH - Y_VALUE_WIDTH - PLOTTER_PADDING_RIGHT;
plotter_height = WSP_HEIGHT - X_VALUE_HEIGHT - PLOTTER_PADDING_TOP;
plotter_pivot_x = Y_VALUE_WIDTH;
plotter_pivot_y = WSP_HEIGHT - X_VALUE_HEIGHT;
if(X_TITLE != "") {
plotter_height -= X_TITLE_HEIGHT;
plotter_pivot_y -= X_TITLE_HEIGHT;
}
if(Y_TITLE != "") {
plotter_width -= Y_TITLE_WIDTH;
plotter_pivot_x += Y_TITLE_WIDTH;
}
ctx.lineWidth = 1;
}
function auto_scale(){
if(data.length >= 1){
var max_arr = [];
var min_arr = [];
for(var i = 0; i < data.length; i++){
if(data[i].length >= 1){
var max = Math.max.apply(null, data[i]);
var min = Math.min.apply(null, data[i]);
max_arr.push(max);
min_arr.push(min);
}
}
var max = Math.max.apply(null, max_arr);
var min = Math.min.apply(null, min_arr);
var MIN_DELTA = 10.0;
if((max - min) < MIN_DELTA){
var mid = (max + min) / 2;
max = mid + MIN_DELTA / 2;
min = mid - MIN_DELTA / 2;
}
var range = max - min;
var exp;
if (range == 0.0)
exp = 0;
else
exp = Math.floor(Math.log10(range / 4));
var scale = Math.pow(10, exp);
var raw_step = (range / 4) / scale;
var step;
potential_steps =[1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 6.0, 8.0, 10.0];
for (var i = 0; i < potential_steps.length; i++) {
if (potential_steps[i] < raw_step)
continue;
step = potential_steps[i] * scale;
Y_MIN = step * Math.floor(min / step);
Y_MAX = Y_MIN + step * (4);
if (Y_MAX >= max)
break;
}
var count = 5 - Math.floor((Y_MAX - max) / step);
Y_MAX = Y_MIN + step * (count - 1);
ctx.font = "16px Arial";
var y_min_text_size = ctx.measureText(Y_MIN.toFixed(1) + "").width;
var y_max_text_size = ctx.measureText(Y_MAX.toFixed(1) + "").width;
Y_VALUE_WIDTH = Math.round(Math.max(y_min_text_size, y_max_text_size)) + 15;
plotter_width = WSP_WIDTH - Y_VALUE_WIDTH - PLOTTER_PADDING_RIGHT;
plotter_pivot_x = Y_VALUE_WIDTH;
}
}
window.onload = plotter_init;
</script>
</head>
<body onresize="canvas_resize()">
<h1 id="header">ESP8266 - Web Plotter</h1>
<canvas id="graph"></canvas>
<br>
<div id="footer">
<div class="sub-footer">
<h2>WebSocket <span id="ws_state"><span style="color: gray">CLOSED</span></span></h2>
</div>
<button id="btn_connect" type="button" onclick="plotter_to_esp8266();">Connect</button>
</div>
</body>
</html>
)=====";
COM6
Connecting to WiFi...
Connected to WiFi
ESP8266 Web Server's IP address IP address: 192.168.0.2
Autoscroll
Clear output
9600 baud
Newline
※ NOTE THAT:
Line-by-line Code Explanation
The above ESP8266 code contains line-by-line explanation. Please read the comments in the code!