SENSORS/ACTUATORS

INTERNET OF THING (IoT)

ESP32 UNO - DIYables Bluetooth App Plotter

Overview

Want to watch a sensor change over time without a PC? With an ESP32 Uno Bluetooth plotter, your phone draws the numbers as moving lines. The ESP32 Uno form board pushes samples, and the DIYables Bluetooth STEM app turns them into a scrolling chart with a legend and labeled axes. Run it as a BLE plotter for Android and iPhone, or as a Classic Bluetooth plotter for Android.

By the end, you can:

Add the DIYables Bluetooth library to Arduino IDE
Flash a BLE or a Classic Bluetooth plot sketch to the ESP32 Uno
Link the phone app and see three test waves scroll in real time
Change the title, axis names, Y range and legend of the sensor graph
Feed the chart from analog pins, an MPU6050 or a smoothing filter

※ NOTE THAT:

The ESP32 Uno radio speaks both BLE and Classic Bluetooth. Choose BLE when an iPhone must connect, or when you want to skip pairing. Choose Classic when every phone is Android and you like the older link with more bandwidth.

What the Plotter App Gives You

This table lists what the app already does, so you only code the data part.

Feature	Details
Series per graph	Up to 10 lines on one chart, each with its own color
Scrolling view	New points enter on the right, old points leave on the left
Axes	Title, X label, Y label and a fixed Y range set from your sketch
Auto-scale	One call lets the app fit the Y axis to the data
Legend	A name for every line, such as Temp or X
Visible samples	You pick how many points stay on screen
Radio modes	BLE for Android and iOS, Classic Bluetooth for Android only

Components You Need

1	×	ESP32 Uno-form Board
1	×	USB Cable Type-A to Type-C (for USB-A PC)
1	×	USB Cable Type-C to Type-C (for USB-C PC)
1	×	Breadboard
1	×	Jumper Wires

Or you can buy the following kits:

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 .

ESP32 Uno Pinout

The printed Uno names on the headers (A0, D7, SDA…) are not what goes into your sketch. Look up each label on this map and copy its GPIO number into the code.

Good to know: the main sketch makes its own test waves, so you wire nothing for the first run. Wires come in only for the sensor examples further down.

Upload and Test the ESP32 Uno Code

At the end of this part, the board streams data and your phone shows a moving chart.

Step 1 — Prepare Arduino IDE

First time with this board? Set it up with ESP32 Uno - Getting Started before you continue.
Build the circuit by following the wiring tables in the examples. For this first test, leave all pins free.
Plug in the USB Type-C cable between the ESP32 Uno and your computer.
Select the board in Arduino IDE: pick ESP32 Dev Module and the COM port of the board (CH340).
Give Bluetooth more flash: open Tools > Partition Scheme and select Huge APP (3MB No OTA/1MB SPIFFS). The normal layout has room for about 1.2 MB of code, and the Bluetooth stack needs more.
Open Library Manager: click the Libraries icon in the left bar.
Search "DIYables Bluetooth" and pick the library published by DIYables.
Click Install.

Search for DIYables Bluetooth created by DIYables and click the Install button.

Newbiely | Arduino IDE 2.3.8

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Library Manager

DIYables Bluetooth

All

DIYables Bluetooth by DIYables

A comprehensive Bluetooth library that connects Arduino to the DIYables Bluetooth STEM mobile app (Android & iOS) via BLE and Classic Bluetooth. Features 11 built-in apps: Monitor, Chat, Digital Pin Control, Joystick, Sliders, Plotter, Analog Gauge, Rotator, Temperature, RTC, and Data Table. Clean architecture with platform abstraction. Works with Arduino Uno R4 WiFi, Arduino Nano 33 BLE, ESP32, and other BLE-capable boards. No mobile coding required. More info

1.0.1

INSTALL

Newbiely.ino

···

1 void setup() {

Output

Serial Monitor

Ln 1, Col 1

ESP32 Dev Module on COM15

Approve the helpers: a pop-up lists extra libraries it depends on. Click Install All.

Next, flash ONE of the two sketches. They draw the same chart; only the radio type is different.

Step 2 — Option A: ESP32 Uno Classic Bluetooth Sketch (Android only)

Good to know: iOS has no Classic Bluetooth support. iPhone users go straight to Option B.

Load the sketch: in Arduino IDE open File Examples DIYables Bluetooth Esp32Bluetooth_Plotter, or paste the code below into an empty sketch.

/* * This ESP32 Uno code was developed by newbiely.com * * This ESP32 Uno code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/esp32-uno/esp32-uno-diyables-bluetooth-app-plotter */ /* * DIYables Bluetooth Library - ESP32 Uno Classic Bluetooth Plotter Example * Talks to the DIYables Bluetooth STEM app on Android phones * Note: iPhones have no Classic Bluetooth. Load the BLE sketch for iOS. * * What this sketch shows (Bluetooth Plotter): * - Numbers are drawn as live lines on the phone screen * - Several lines (series) can share one graph * - Title, axis names, Y range and legend are set in code * * Board: ESP32 Uno form board (Classic Bluetooth radio) * * Note: in Arduino IDE pick Tools > Partition Scheme > * "Huge APP (3MB No OTA/1MB SPIFFS)", the Bluetooth stack is big * * How to use: * 1. Upload this sketch to the ESP32 Uno * 2. Open the Serial Monitor at 115200 baud to follow the link status * 3. Pair the phone, connect with the DIYables Bluetooth App and open the plot * * Tutorial: https://diyables.io/bluetooth-app * Author: DIYables */ #include <DIYables_BluetoothServer.h> #include <DIYables_BluetoothPlotter.h> #include <platforms/DIYables_Esp32Bluetooth.h> // Classic Bluetooth link (name seen by the phone) and the app server DIYables_Esp32Bluetooth bluetooth("ESP32_Plotter"); DIYables_BluetoothServer bluetoothServer(bluetooth); // the plotter screen object DIYables_BluetoothPlotter bluetoothPlotter; // timing and wave state for the test signals unsigned long lastPlotTime = 0; const unsigned long PLOT_INTERVAL = 100; // one new sample every 100 ms float phase = 0; void setup() { Serial.begin(115200); delay(1000); Serial.println("DIYables Bluetooth - ESP32 Plotter Example"); // start the Classic Bluetooth server on the ESP32 Uno bluetoothServer.begin(); // register the plotter screen with the server bluetoothServer.addApp(&bluetoothPlotter); // look of the graph: title, axes, fixed Y range, sample count, legend bluetoothPlotter.setPlotTitle("Sensor Data"); bluetoothPlotter.setAxisLabels("Time", "Value"); bluetoothPlotter.setYAxisRange(-15, 30); // Y axis stays between -15 and 30 bluetoothPlotter.setMaxSamples(100); // keep 100 points on screen bluetoothPlotter.setLegendLabels("Sine", "Cosine", "Tangent"); // one name per line // remove the // below to let the app fit the Y axis by itself // bluetoothPlotter.enableAutoScale(true); // print a message when a phone links or leaves bluetoothServer.setOnConnected([]() { Serial.println("Bluetooth connected!"); }); bluetoothServer.setOnDisconnected([]() { Serial.println("Bluetooth disconnected!"); }); // optional: runs when the app opens the plot and asks for data bluetoothPlotter.onDataRequest([]() { Serial.println("App requested plot data"); }); Serial.println("Waiting for Bluetooth connection..."); } void loop() { // keep the Bluetooth link alive bluetoothServer.loop(); // time for a new sample? if (millis() - lastPlotTime >= PLOT_INTERVAL) { lastPlotTime = millis(); // make three test waves float sine = sin(phase); float cosine = cos(phase); float tangent = tan(phase) * 0.3; // shrink the tangent peaks // push the three values to the phone graph bluetoothPlotter.send(sine, cosine, tangent); // same numbers to the Serial Monitor / Serial Plotter Serial.print(sine, 2); Serial.print(" "); Serial.print(cosine, 2); Serial.print(" "); Serial.println(tangent, 2); phase += 0.1; if (phase > 2 * PI) { phase = 0; } // TODO: put real ESP32 Uno sensor readings here, for example: // - one sensor: bluetoothPlotter.send(temperature); // - three axes: bluetoothPlotter.send(accelX, accelY, accelZ); // - several sensors: bluetoothPlotter.send(sensor1, sensor2, sensor3); } delay(10); }

Upload: hit the Upload button.
Open the Serial Monitor at 115200 baud. Right after a reset it prints:

Newbiely | Arduino IDE 2.3.8

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Newbiely.ino

···

8 Serial.println("Hello World!");

Output

Serial Monitor

Message (Enter to send message to 'ESP32 Dev Module' on 'COM15')

New Line

9600 baud

DIYables Bluetooth - ESP32 Plotter Example Waiting for Bluetooth connection...

Ln 11, Col 1

ESP32 Dev Module on COM15

Step 2 — Option B: ESP32 Uno BLE Sketch (Android and iOS)

Load the sketch: open File Examples DIYables Bluetooth Esp32BLE_Plotter, or paste the code below.

/* * This ESP32 Uno code was developed by newbiely.com * * This ESP32 Uno code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/esp32-uno/esp32-uno-diyables-bluetooth-app-plotter */ /* * DIYables Bluetooth Library - ESP32 Uno BLE Plotter Example * Pairs with the DIYables Bluetooth STEM app on Android and iOS * * What this sketch shows (Bluetooth Plotter): * - Numbers are drawn as live lines on the phone screen * - Several lines (series) can share one graph * - Title, axis names, Y range and legend are set in code * * Board: ESP32 Uno form board (BLE radio) * * Note: in Arduino IDE pick Tools > Partition Scheme > * "Huge APP (3MB No OTA/1MB SPIFFS)", the BLE stack is big * * How to use: * 1. Upload this sketch to the ESP32 Uno * 2. Open the Serial Monitor at 115200 baud to follow the link status * 3. Connect with the DIYables Bluetooth App and open the plot * * Tutorial: https://diyables.io/bluetooth-app * Author: DIYables */ #include <DIYables_BluetoothServer.h> #include <DIYables_BluetoothPlotter.h> #include <platforms/DIYables_Esp32BLE.h> // BLE name and UUIDs the app looks for const char* DEVICE_NAME = "ESP32BLE_Plotter"; const char* SERVICE_UUID = "19B10000-E8F2-537E-4F6C-D104768A1214"; const char* TX_UUID = "19B10001-E8F2-537E-4F6C-D104768A1214"; const char* RX_UUID = "19B10002-E8F2-537E-4F6C-D104768A1214"; // BLE link object and the server that runs the apps DIYables_Esp32BLE bluetooth(DEVICE_NAME, SERVICE_UUID, TX_UUID, RX_UUID); DIYables_BluetoothServer bluetoothServer(bluetooth); // the plotter screen object DIYables_BluetoothPlotter bluetoothPlotter; // timing and wave state for the test signals unsigned long lastPlotTime = 0; const unsigned long PLOT_INTERVAL = 100; float phase = 0; void setup() { Serial.begin(115200); delay(1000); Serial.println("DIYables Bluetooth - ESP32 BLE Plotter Example"); // start the BLE server on the ESP32 Uno bluetoothServer.begin(); // register the plotter screen with the server bluetoothServer.addApp(&bluetoothPlotter); // look of the graph: title, axes, fixed Y range, sample count, legend bluetoothPlotter.setPlotTitle("Sensor Data"); bluetoothPlotter.setAxisLabels("Time", "Value"); bluetoothPlotter.setYAxisRange(-15, 30); bluetoothPlotter.setMaxSamples(100); bluetoothPlotter.setLegendLabels("Sine", "Cosine", "Tangent"); // print a message when a phone links or leaves bluetoothServer.setOnConnected([]() { Serial.println("Bluetooth connected!"); }); bluetoothServer.setOnDisconnected([]() { Serial.println("Bluetooth disconnected!"); }); // runs when the app opens the plot and asks for data bluetoothPlotter.onDataRequest([]() { Serial.println("App requested plot data"); }); Serial.println("Waiting for Bluetooth connection..."); } void loop() { bluetoothServer.loop(); if (millis() - lastPlotTime >= PLOT_INTERVAL) { lastPlotTime = millis(); float sine = sin(phase); float cosine = cos(phase); float tangent = tan(phase) * 0.3; bluetoothPlotter.send(sine, cosine, tangent); Serial.print(sine, 2); Serial.print(" "); Serial.print(cosine, 2); Serial.print(" "); Serial.println(tangent, 2); phase += 0.1; if (phase > 2 * PI) { phase = 0; } } delay(10); }

Upload it with the Upload button.
Check the Serial Monitor at 115200 baud:

Newbiely | Arduino IDE 2.3.8

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☐

Newbiely.ino

···

8 Serial.println("Hello World!");

Output

Serial Monitor

Message (Enter to send message to 'ESP32 Dev Module' on 'COM15')

New Line

9600 baud

DIYables Bluetooth - ESP32 BLE Plotter Example Waiting for Bluetooth connection...

Ln 11, Col 1

ESP32 Dev Module on COM15

Pro tip: close the Arduino IDE Serial Plotter window before you open the Serial Monitor. Both want the same COM port, and only one can hold it.

Step 3 — Connect the Phone App

When this step is done, three colored waves move across your phone.

Get the app: DIYables Bluetooth App for Android or iOS.
Classic sketch only — pair first: go to Settings > Bluetooth on the Android phone, switch Bluetooth on, tap "ESP32_Plotter", accept the request (no PIN), and wait until it says "Paired". With the BLE sketch, skip this step.
Start the app and grant access on the first launch:

Nearby Devices (Android 12 or newer) or Bluetooth (iOS) — needed to find and link the board
Location (Android 11 or older) — old Android versions ask for it before a BLE scan

Make sure phone Bluetooth is on.

Scan: tap Connect on the home screen. BLE and Classic devices both appear.

DIYables Bluetooth App - Home Screen with Scan Button

Pick your board: "ESP32_Plotter" for Classic, or "ESP32BLE_Plotter" for BLE. Once linked, the app jumps back home.
Open the chart: choose Plotter in the app menu.

DIYables Bluetooth App - Home Screen with Plotter App

Watch it run: the sine, cosine and tangent lines slide from right to left.

Pro tip: the gear icon on the home screen hides app tiles you never use. Every screen is covered in the DIYables Bluetooth App User Manual.

The Serial Monitor now logs the link and the exact numbers the chart draws, one line per sample:

Newbiely | Arduino IDE 2.3.8

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☐

Newbiely.ino

···

8 Serial.println("Hello World!");

Output

Serial Monitor

Message (Enter to send message to 'ESP32 Dev Module' on 'COM15')

New Line

9600 baud

Bluetooth connected! App requested plot data 0.84 0.54 0.47 0.89 0.45 0.59 0.93 0.36 0.77 0.96 0.27 1.08

Ln 11, Col 1

ESP32 Dev Module on COM15

How the Sketch Works

Here is what each part of the ESP32 Uno plot sketch does.

Code Part	What It Does
DIYables_Esp32BLE or DIYables_Esp32Bluetooth	Starts the radio under the name the phone lists
bluetoothServer.addApp(&bluetoothPlotter)	Puts the Plotter screen on the Bluetooth server
setPlotTitle / setAxisLabels / setYAxisRange	Sets the chart text and a Y scale from -15 to 30
setMaxSamples(100) and setLegendLabels()	Keeps 100 points visible and names the three lines
loop() with PLOT_INTERVAL	Every 100 ms makes sine, cosine and 0.3 x tangent, then calls send()
Serial.print lines	Copy the same three values to the Serial Monitor

The result is a chart that gets ten new points per second. The tangent is scaled by 0.3, so most of its tall spikes stay inside the Y range.

ESP32 Uno vs UNO R4 for This Project

Porting this plotter from the UNO R4 WiFi to the ESP32 Uno mostly swaps the radio library and the board settings.

Item	Arduino UNO R4 WiFi	ESP32 Uno
Logic voltage	5V	3.3V
Bluetooth	BLE only	BLE and Classic Bluetooth
Library platform file	DIYables_ArduinoBLE.h	DIYables_Esp32BLE.h or DIYables_Esp32Bluetooth.h
Example sketch	ArduinoBLE_Plotter	Esp32BLE_Plotter or Esp32Bluetooth_Plotter
Analog plot pins	A0, A1, A2	A0 (GPIO2), A1 (GPIO4), A2 (GPIO35)
ADC range	0 to 1023 (10-bit)	0 to 4095 (12-bit) plus analogSetAttenuation(ADC_11db)
Arduino IDE board	Arduino UNO R4 WiFi	ESP32 Dev Module with Huge APP partition

The test sketch has no wiring, so nothing moves. For analog sensors, keep the same header positions, but keep each signal at 3.3V or less, and change 1023 to 4095 and 5.0 to 3.3 in old R4 math.

Shape the Chart for Your Project

At the end of this part, the chart shows your own data with your own labels.

Set Title, Axes and Legend

Call these in setup(). They decide how the chart looks before the first point arrives.

// chart name at the top bluetoothPlotter.setPlotTitle("Sensor Data"); // text under the X axis and beside the Y axis bluetoothPlotter.setAxisLabels("Time", "Value"); // lock the Y axis to a fixed window bluetoothPlotter.setYAxisRange(-15, 30); // or let the app pick the window from the data bluetoothPlotter.enableAutoScale(true); // how many points stay on screen bluetoothPlotter.setMaxSamples(100); // one legend name per line bluetoothPlotter.setLegendLabels("Sine", "Cosine", "Tangent"); // 1, 2 or 4 names work as well: // bluetoothPlotter.setLegendLabels("Temperature"); // bluetoothPlotter.setLegendLabels("Temp", "Humidity"); // bluetoothPlotter.setLegendLabels("Ch1", "Ch2", "Ch3", "Ch4");

Push Samples

send() has several forms. The number of values you pass is the number of lines you get.

// one line bluetoothPlotter.send(25.3); // two lines bluetoothPlotter.send(temperature, humidity); // three lines bluetoothPlotter.send(sine, cosine, tangent); // four lines bluetoothPlotter.send(ch1, ch2, ch3, ch4); // an array, for any number of lines float values[] = {1.0, 2.0, 3.0, 4.0, 5.0}; bluetoothPlotter.send(values, 5); // a ready-made comma list bluetoothPlotter.send("1.23,4.56,7.89");

React When the App Asks

The app may ask for data when the Plotter screen opens. This callback runs at that moment.

bluetoothPlotter.onDataRequest([]() { Serial.println("App requested plot data"); // you can push a first sample here });

Log Connect and Disconnect

These hooks fire when the phone joins or leaves. Use them for a status LED or to pause sampling.

bluetoothServer.setOnConnected([]() { Serial.println("Bluetooth connected!"); }); bluetoothServer.setOnDisconnected([]() { Serial.println("Bluetooth disconnected!"); });

Reading the Plot Screen

Know how the screen and the data format work, and you can pick a good send rate.

Item	Meaning
Line chart	Each series is one colored line that scrolls on its own
Legend	Matches each color to the name from setLegendLabels()
Auto-scroll	The newest sample is always at the right edge
Data format	Each sample travels as float values split by commas
Send rate	10 to 100 ms between samples gives a smooth line

Real Data Examples

Each snippet shows only the parts that change. Keep the Bluetooth setup lines from the full sketch above.

Example 1 — One Temperature Line

This draws a single line ten times per second. Swap readTemperatureSensor() for the read call of your sensor.

unsigned long lastPlotTime = 0; const unsigned long PLOT_INTERVAL = 100; // 10 samples per second void setup() { bluetoothPlotter.setPlotTitle("Temperature"); bluetoothPlotter.setAxisLabels("Time", "°C"); bluetoothPlotter.setYAxisRange(0, 50); bluetoothPlotter.setLegendLabels("Temperature"); } void loop() { bluetoothServer.loop(); if (millis() - lastPlotTime >= PLOT_INTERVAL) { lastPlotTime = millis(); float temperature = readTemperatureSensor(); bluetoothPlotter.send(temperature); } delay(10); }

Example 2 — MPU6050 Tilt and Shake

The MPU6050 uses I2C. On the ESP32 Uno, A4 and A5 are not I2C, so connect the module to the SDA (GPIO21) and SCL (GPIO22) header pins. Wire.begin() picks them by default.

MPU6050 Pin	ESP32 Uno Pin
VCC	3.3V
GND	GND
SDA	SDA (GPIO21)
SCL	SCL (GPIO22)

#include <Wire.h> #include <MPU6050.h> MPU6050 mpu; unsigned long lastPlotTime = 0; void setup() { Wire.begin(); // ESP32 Uno: SDA (GPIO21), SCL (GPIO22) mpu.initialize(); bluetoothPlotter.setPlotTitle("Accelerometer"); bluetoothPlotter.setAxisLabels("Time", "g"); bluetoothPlotter.setYAxisRange(-2.0, 2.0); bluetoothPlotter.setLegendLabels("X", "Y", "Z"); } void loop() { bluetoothServer.loop(); if (millis() - lastPlotTime >= 50) { // 20 samples per second lastPlotTime = millis(); int16_t ax, ay, az; mpu.getAcceleration(&ax, &ay, &az); float gx = ax / 16384.0; float gy = ay / 16384.0; float gz = az / 16384.0; bluetoothPlotter.send(gx, gy, gz); } delay(10); }

Example 3 — Three Analog Inputs

Three sensors on A0, A1 and A2 share one chart. Each channel returns a 12-bit number, which is why the chart scale runs 0 to 4095.

Sensor Output	ESP32 Uno Pin
Sensor 1 signal	A0 (GPIO2)
Sensor 2 signal	A1 (GPIO4)
Sensor 3 signal	A2 (GPIO35)
Sensor VCC	3.3V
Sensor GND	GND

A0 (GPIO2) is a boot strapping pin. A sensor that pulls it HIGH during reset or upload can stop the board from flashing. If that happens, unplug the A0 signal while you upload. Also, ESP32 Uno pins are not 5V tolerant, so power the sensors from 3.3V or add a divider.

Good to know: A2 (GPIO35) is an input-only pin. That is fine here, because the sketch only reads it.

const int ANALOG_PINS[] = {2, 4, 35}; // A0 (GPIO2), A1 (GPIO4), A2 (GPIO35) const int NUM_CHANNELS = 3; unsigned long lastPlotTime = 0; void setup() { // set the ADC attenuation to 11 dB (up to ~3.3V input) analogSetAttenuation(ADC_11db); bluetoothPlotter.setPlotTitle("Analog Inputs"); bluetoothPlotter.setAxisLabels("Time", "ADC Value"); bluetoothPlotter.setYAxisRange(0, 4095); bluetoothPlotter.setMaxSamples(200); bluetoothPlotter.setLegendLabels("A0", "A1", "A2"); } void loop() { bluetoothServer.loop(); if (millis() - lastPlotTime >= 100) { lastPlotTime = millis(); float values[NUM_CHANNELS]; for (int i = 0; i < NUM_CHANNELS; i++) { values[i] = analogRead(ANALOG_PINS[i]); } bluetoothPlotter.send(values, NUM_CHANNELS); } delay(10); }

Good to know: analogSetAttenuation(ADC_11db) lets each ESP32 Uno analog pin read the full span, from 0V up to about 3.3V. Without a wide range, readings reach 4095 too early and the lines sit flat at the top of the chart.

Example 4 — Test Signal Generator

No sensor is needed. The sketch makes a sine, a square and a triangle wave, so you can compare shapes on the phone.

float phase = 0; unsigned long lastPlotTime = 0; void setup() { bluetoothPlotter.setPlotTitle("Signal Generator"); bluetoothPlotter.setAxisLabels("Time", "Amplitude"); bluetoothPlotter.setYAxisRange(-1.5, 1.5); bluetoothPlotter.setLegendLabels("Sine", "Square", "Triangle"); } void loop() { bluetoothServer.loop(); if (millis() - lastPlotTime >= 50) { lastPlotTime = millis(); float sine = sin(phase); float square = (sin(phase) > 0) ? 1.0 : -1.0; float triangle = 2.0 * abs(fmod(phase / PI, 2.0) - 1.0) - 1.0; bluetoothPlotter.send(sine, square, triangle); phase += 0.1; if (phase > 2 * PI) phase -= 2 * PI; } delay(10); }

Cleaner Lines and Switchable Views

Raw sensor data is often jumpy. These two helpers smooth it and let one chart show different data.

Moving Average Filter

The class keeps the last 10 samples and returns their mean. The sketch plots the raw voltage on A0 (GPIO2) next to the smoothed one. The math uses 3.3 and 4095 for the 12-bit ESP32 Uno ADC.

class MovingAverage { float buffer[10]; int index = 0; int count = 0; public: float add(float value) { buffer[index] = value; index = (index + 1) % 10; if (count < 10) count++; float sum = 0; for (int i = 0; i < count; i++) sum += buffer[i]; return sum / count; } }; MovingAverage filter1, filter2; unsigned long lastPlotTime = 0; void setup() { // set the ADC attenuation to 11 dB (up to ~3.3V input) analogSetAttenuation(ADC_11db); } void loop() { bluetoothServer.loop(); if (millis() - lastPlotTime >= 100) { lastPlotTime = millis(); float raw = analogRead(2) * 3.3 / 4095.0; // A0 (GPIO2) in volts float filtered = filter1.add(raw); // two lines: raw and smoothed bluetoothPlotter.send(raw, filtered); } delay(10); }

Change the View at Run Time

Call one of these, for example from a button handler, to switch the chart between two modes.

// swap chart settings while the sketch runs void switchToTemperatureMode() { bluetoothPlotter.setPlotTitle("Temperature Monitor"); bluetoothPlotter.setAxisLabels("Time", "°C"); bluetoothPlotter.setYAxisRange(-10, 50); bluetoothPlotter.setLegendLabels("Internal", "External"); } void switchToVoltageMode() { bluetoothPlotter.setPlotTitle("Voltage Monitor"); bluetoothPlotter.setAxisLabels("Time", "V"); bluetoothPlotter.setYAxisRange(0, 3.3); bluetoothPlotter.setLegendLabels("Ch1", "Ch2", "Ch3"); }

Choosing BLE or Classic on the ESP32 Uno

The ESP32 Uno runs either sketch. Use this table to decide.

Point	BLE sketch (Esp32BLE_Plotter)	Classic sketch (Esp32Bluetooth_Plotter)
iPhone	Works	Does not work
Android	Works	Works
Current draw	Lower	Higher
Typical range	About 30 to 100 m	About 10 to 100 m
Data speed	Lower	Higher
Pairing in phone settings	Not needed	Needed once
Name in scan list	ESP32BLE_Plotter	ESP32_Plotter

For three lines at 10 samples per second, BLE has enough speed. If you plot many lines very fast on Android, Classic gives more headroom.

Debug Helper

When a line looks odd, print what you send and the free memory, then compare the Serial Monitor with the chart.

void debugPlotterData(float v1, float v2, float v3) { Serial.println("=== Plotter Debug ==="); Serial.println("Value 1: " + String(v1, 2)); Serial.println("Value 2: " + String(v2, 2)); Serial.println("Value 3: " + String(v3, 2)); Serial.println("Free Heap: " + String(ESP.getFreeHeap())); Serial.println("====================="); }

Build Ideas

Area	Plot Projects
Room and weather	Temperature and humidity trend, daylight curve, air pressure log
Motion	Accelerometer shake test, tilt angle over time, step counter signal
Signals	Sound level view, vibration check, pulse sensor waveform, magnetic field strength
Classroom	Sine and cosine compare, RC charge curve, PID step response, physics lab log
Tutorial	Motor vibration, process value trend, power draw log, quality check chart

Mix the Plotter with Other Bluetooth Apps

One Bluetooth server on the ESP32 Uno can host several app screens at the same time.

Plotter Plus Slider

Two sliders change the frequency and the amplitude of the plotted wave.

float frequency = 1.0; float amplitude = 1.0; bluetoothSlider.onSliderValue([](int slider1, int slider2) { frequency = map(slider1, 0, 100, 1, 20) / 10.0; amplitude = slider2 / 100.0; }); // inside loop(): float value = amplitude * sin(phase * frequency); bluetoothPlotter.send(value);

Plotter Plus Table

The chart shows the trend, and the table lists the exact numbers.

bluetoothTable.sendValueUpdate("Current", String(currentValue, 2)); bluetoothTable.sendValueUpdate("Max", String(maxValue, 2)); bluetoothTable.sendValueUpdate("Min", String(minValue, 2)); bluetoothTable.sendValueUpdate("Average", String(average, 2));

Try These Next

With the chart working, build on it with these ESP32 Uno Bluetooth pages:

ESP32 Uno - Bluetooth Temperature — a thermometer-style screen
ESP32 Uno - Bluetooth Analog Gauge — one value on a needle dial
ESP32 Uno - Bluetooth Table — many readings in rows
ESP32 Uno - Multiple Bluetooth Apps — run the plotter next to other screens

Where to Get Help

The API reference that comes with the DIYables Bluetooth library
More app guides on diyables.io/bluetooth-app
The Arduino community forums

Troubleshooting

Problem	Possible Cause	Solution
No COM port appears in Arduino IDE	CH340 driver missing or a charge-only cable	Install the CH340 driver and use a USB Type-C cable that carries data
Upload stops at "Failed to connect" or "Waiting for download"	The board did not enter download mode	Hold the BOOT button while the upload starts, then let go
Board does not boot or upload with a sensor on A0	A0 (GPIO2) is a boot strapping pin pulled the wrong way	Unplug the module while uploading, or use another pin
Compiler says the sketch is too big	Default partition has no room for Bluetooth	Choose Tools > Partition Scheme > Huge APP (3MB No OTA/1MB SPIFFS)
Board name is missing in the app scan	Sketch not running, phone Bluetooth off, or Classic not paired	Check that the Serial Monitor shows "Waiting for Bluetooth connection...", pair ESP32_Plotter first for Classic, and turn on Location on Android 11 or older
ESP32_Plotter never shows on an iPhone	iOS has no Classic Bluetooth	Upload the BLE sketch and connect to ESP32BLE_Plotter
Chart is connected but the lines do not move	The Plotter screen is not open or send() is not reached	Open Plotter in the app menu and make sure bluetoothServer.loop() and send() run in loop()
Lines look steppy or jerky	Samples sent too slowly or too many series over BLE	Send every 50 to 100 ms and drop series you do not need
Analog lines are stuck at 4095	Signal above 3.3V or attenuation missing	Keep analogSetAttenuation(ADC_11db) and add a divider so the pin stays under 3.3V
Accelerometer chart shows flat zero lines	I2C wires sit on A4 and A5, which are plain analog inputs here	Rewire the module to the header pins marked SDA (GPIO21) and SCL (GPIO22)

FAQ

BLE or Classic Bluetooth — which should my ESP32 Uno plotter use?

Use BLE if any phone is an iPhone or you do not want a pairing step. Use Classic if every phone is Android and you plan to stream many lines at a high rate. Both sketches draw the same chart.

Can I try the phone graph before I connect any sensor?

Yes. The example makes sine, cosine and tangent values in code, so the chart moves with no wiring at all. Later, replace those three lines with your sensor reads.

How many lines can one chart show?

The app draws up to 10 series. Pass that many values to send(), or use the array form send(values, count). Give each line a name with setLegendLabels().

Why do my analog lines go up to 4095 and not 1023?

The ESP32 Uno ADC is 12-bit, so analogRead() returns 0 to 4095. For raw counts, give setYAxisRange() the limits 0 and 4095. To plot volts, use value * 3.3 / 4095.0.

What job does analogSetAttenuation(ADC_11db) do in the analog plot code?

It opens the ESP32 Uno ADC window to about 0 to 3.3V, so the whole sensor swing fills 0 to 4095. Without it, the value tops out early and the line flattens at the top. UNO R4 sketches never had this line; it is only for the ESP32 Uno. Never let the sensor signal climb past 3.3V.

Do A0 and A1 still read while Bluetooth is running?

Yes. The ADC2 limit on A0 (GPIO2) and A1 (GPIO4) comes from WiFi, not Bluetooth. If you later add WiFi to the same sketch, move those sensors to A2 to A5 (GPIO35, 34, 36, 39) or GPIO32/33 and change the pin numbers.

Can I plug a 5V sensor into the ESP32 Uno for plotting?

The sensor can run on 5V, but its output must reach the pin at 3.3V or less. A 5V level can harm an ESP32 Uno input. Use a resistor divider or a level shifter, and scale the math to match.

Is moving an older ArduinoBLE plotter sketch to the ESP32 Uno a big job?

Only a little. Swap DIYables_ArduinoBLE.h for DIYables_Esp32BLE.h, use the DIYables_Esp32BLE object with the same UUIDs, and pick ESP32 Dev Module with the Huge APP partition. The plotter calls stay the same.

Can I use the Arduino IDE Serial Plotter at the same time?

The sketch prints the same three numbers split by spaces, so the IDE Serial Plotter can draw them over USB. Only one window can hold the COM port, though, so close the Serial Monitor first.

What if my plot needs more pins than the Uno headers give?

The ESP32 Uno has a few extra holes near the power header: GPIO32 and GPIO33 (I/O, PWM, analog on ADC1, so they still read while WiFi is on) and GPIO15 (I/O, PWM, analog on ADC2). Solder a pin header into the hole and write its GPIO number in the sketch. For a fourth or fifth analog line on the chart, GPIO32 and GPIO33 are the best picks. Two warnings apply. First, GPIO15 and GPIO0 (the IO0 pin at the unused Uno NC position) are boot strapping pins, and a wrong connection can stop the board from booting or uploading code, so use GPIO32/33 first. Second, never use the six holes under the digital header (SD0 to SD3, CMD, CLK = GPIO6 to GPIO11), because they connect to the flash chip and using them crashes the board.

Can I see the same graph in a web browser instead?

Yes. The ESP32 Uno also has WiFi. The ESP32 Uno - Web Plotter page draws live lines on any phone or PC browser.

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