SENSORS/ACTUATORS

INTERNET OF THING (IoT)

ESP32 UNO - DIYables Bluetooth App Table

Overview

Too many numbers scrolling past in the Serial Monitor? Put them in an ESP32 Uno Bluetooth table instead, where every reading keeps its own line. The ESP32 Uno form board sends a label and a value for each row, and the free DIYables Bluetooth STEM app shows them as a neat two-column list that refreshes live. Use it as a wireless sensor dashboard, a key-value status panel or a quick debug screen.

By the end, you can:

Install the DIYables Bluetooth library in Arduino IDE
Flash either the BLE or the Classic Bluetooth table sketch
Link your phone and watch seven or eight rows change every second
Add, rename, clear and refill rows from your own code
Fill the rows with real data from a DHT11, analog sensors or input pins

※ NOTE THAT:

The ESP32 Uno chip carries two Bluetooth radios: BLE and Classic. The BLE sketch connects to Android phones and iPhones with no pairing step. The Classic sketch connects to Android only, because iOS does not allow Classic Bluetooth for apps like this one.

What the Table Screen Offers

This list tells you what the library already handles, so you only write the data part.

Feature	Details
Row limit	Up to 20 rows, each with its own label
Single-row refresh	You push one value, and only that cell changes
Label and value	The left cell is the name, the right cell is any text you send
Layout sync	On connect, the app asks the board for the row names
Radio choice	BLE for Android and iOS, Classic Bluetooth for Android only
Power	BLE draws less current than Classic Bluetooth

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
1	×	Optionally, DHT11 Temperature Humidity Sensor Module
1	×	Alternatively, DHT11 Sensor
1	×	Optionally, LED
1	×	Alternatively, Button and LED Kit
1	×	Optionally, 220 ohm Resistor

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

Your sketch never uses the printed Uno label, only the GPIO number behind it. Look up D3 and D13 on this map before you plug in the optional demo parts.

How to Connect (Video Demo Only)

After this part, the optional DHT11 and LED sit on the right pins. The two main example sketches send test values, so for them you only need the board and a USB cable.

Component Pin	ESP32 Uno Pin
DHT11 VCC	3.3V
DHT11 GND	GND
DHT11 DATA	D3 (GPIO25)
LED Anode (+) through 220 ohm resistor	D13 (GPIO18)
LED Cathode (-)	GND

Good to know: this board has no built-in LED for the demo, so the demo drives an external LED on D13 (GPIO18). Power the DHT11 from 3.3V, because ESP32 Uno pins are not 5V tolerant.

Upload and Test the ESP32 Uno Code

When you finish this part, the board advertises itself over Bluetooth and fills the table with test values.

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 table above. Skip it if you only run the main sketches.
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 enough flash: open Tools > Partition Scheme and select Huge APP (3MB No OTA/1MB SPIFFS). The default layout keeps only about 1.2 MB for your program.
Open Library Manager: click the Libraries icon on the left side of the IDE.
Search "DIYables Bluetooth" and find 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

Add the helpers: a window lists extra libraries the package needs. Click Install All.

Next, flash ONE of the two sketches. Both build the same table; they differ only in the radio.

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

Good to know: an iPhone will never list this sketch. For iOS, go to Option B.

Load the sketch: in Arduino IDE choose File Examples DIYables Bluetooth Esp32Bluetooth_Table, 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-table */ /* * DIYables Bluetooth Library - ESP32 Uno Classic Bluetooth Table sketch * Shows rows of data in the DIYables Bluetooth STEM app on Android phones * Note: iPhones cannot use Classic Bluetooth. Pick the BLE sketch for iOS. * * What this sketch shows: * - a two-column table (name and value) on the phone * - each row gets a fresh value while the phone is linked * - a quick way to build a status board or sensor panel * * Board: ESP32 Uno form board (Arduino IDE board "ESP32 Dev Module") * * Tip: pick Tools > Partition Scheme > "Huge APP (3MB No OTA/1MB SPIFFS)" * because the Bluetooth code is too big for the default partition * * How to try it: * 1. Upload this sketch to the ESP32 Uno * 2. Open the Serial Monitor at 115200 baud to follow the link state * 3. Pair the phone, connect with the DIYables Bluetooth App and open the Table screen * * Tutorial: https://diyables.io/bluetooth-app * Author: DIYables */ #include <DIYables_BluetoothServer.h> #include <DIYables_BluetoothTable.h> #include <platforms/DIYables_Esp32Bluetooth.h> // Classic Bluetooth link with the name shown on the phone DIYables_Esp32Bluetooth bluetooth("ESP32_Table"); DIYables_BluetoothServer bluetoothServer(bluetooth); // the Table screen of the app DIYables_BluetoothTable bluetoothTable; // timer and counter for the test values unsigned long lastUpdate = 0; const unsigned long UPDATE_INTERVAL = 1000; // one refresh per second int counter = 0; void setup() { Serial.begin(115200); delay(1000); Serial.println("DIYables Bluetooth - ESP32 Table Example"); // start the Classic Bluetooth server on the ESP32 Uno bluetoothServer.begin(); // register the Table screen with the server bluetoothServer.addApp(&bluetoothTable); // the row names, from top to bottom bluetoothTable.addRow("Temperature"); bluetoothTable.addRow("Humidity"); bluetoothTable.addRow("Pressure"); bluetoothTable.addRow("Counter"); bluetoothTable.addRow("Uptime"); bluetoothTable.addRow("Free Heap"); bluetoothTable.addRow("CPU Freq"); bluetoothTable.addRow("Status"); Serial.print("Table rows defined: "); Serial.println(bluetoothTable.getRowCount()); // runs when a phone links up or drops the link bluetoothServer.setOnConnected([]() { Serial.println("Bluetooth connected!"); // first the row names bluetoothTable.sendTableStructure(); // then the first set of values updateTableValues(); }); bluetoothServer.setOnDisconnected([]() { Serial.println("Bluetooth disconnected!"); }); // optional: the app asks for the rows again bluetoothTable.onDataRequest([]() { Serial.println("App requested table data"); bluetoothTable.sendTableStructure(); updateTableValues(); }); Serial.println("Waiting for Bluetooth connection..."); } // fills every row with a new value void updateTableValues() { // swap these test numbers for your real sensor readings // fake temperature between 20 and 30 °C float temperature = 20.0 + random(0, 100) / 10.0; bluetoothTable.sendValueUpdate("Temperature", String(temperature, 1) + " °C"); // fake humidity between 40 and 60 % int humidity = 40 + random(0, 21); bluetoothTable.sendValueUpdate("Humidity", String(humidity) + " %"); // fake air pressure between 1000 and 1020 hPa int pressure = 1000 + random(0, 21); bluetoothTable.sendValueUpdate("Pressure", String(pressure) + " hPa"); // a number that goes up by one each time bluetoothTable.sendValueUpdate("Counter", String(counter)); counter++; // time since power-on, shown as hours, minutes and seconds unsigned long uptime = millis() / 1000; String uptimeStr = String(uptime / 3600) + "h " + String((uptime % 3600) / 60) + "m " + String(uptime % 60) + "s"; bluetoothTable.sendValueUpdate("Uptime", uptimeStr); // real free RAM of the ESP32 Uno bluetoothTable.sendValueUpdate("Free Heap", String(ESP.getFreeHeap()) + " bytes"); // real clock speed of the ESP32 Uno CPU bluetoothTable.sendValueUpdate("CPU Freq", String(ESP.getCpuFreqMHz()) + " MHz"); // a status word that flips each update bluetoothTable.sendValueUpdate("Status", counter % 2 == 0 ? "Running" : "Active"); Serial.println("Table values updated"); } void loop() { // keep the Bluetooth link working bluetoothServer.loop(); // refresh the rows once per interval, only while a phone is linked if (bluetooth.isConnected() && millis() - lastUpdate >= UPDATE_INTERVAL) { lastUpdate = millis(); updateTableValues(); } delay(10); }

Upload: press the Upload button.
Open the Serial Monitor at 115200 baud. 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 Table Example Table rows defined: 8 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: choose File Examples DIYables Bluetooth Esp32BLE_Table, 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-table */ /* * DIYables Bluetooth Library - ESP32 Uno BLE Table sketch * Shows rows of data in the DIYables Bluetooth STEM app on Android phones and iPhones * * What this sketch shows: * - a two-column table (name and value) on the phone * - each row gets a fresh value while the phone is linked * - a quick way to build a status board or sensor panel * * Board: ESP32 Uno form board (Arduino IDE board "ESP32 Dev Module") * * Tip: pick Tools > Partition Scheme > "Huge APP (3MB No OTA/1MB SPIFFS)" * because the Bluetooth code is too big for the default partition * * How to try it: * 1. Upload this sketch to the ESP32 Uno * 2. Open the Serial Monitor at 115200 baud to follow the link state * 3. Connect with the DIYables Bluetooth App and open the Table screen * * Tutorial: https://diyables.io/bluetooth-app * Author: DIYables */ #include <DIYables_BluetoothServer.h> #include <DIYables_BluetoothTable.h> #include <platforms/DIYables_Esp32BLE.h> // BLE name and UUIDs that the app looks for const char* DEVICE_NAME = "ESP32BLE_Table"; 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 on top of it DIYables_Esp32BLE bluetooth(DEVICE_NAME, SERVICE_UUID, TX_UUID, RX_UUID); DIYables_BluetoothServer bluetoothServer(bluetooth); // the Table screen of the app DIYables_BluetoothTable bluetoothTable; // timer and counter for the test values unsigned long lastUpdate = 0; const unsigned long UPDATE_INTERVAL = 1000; int counter = 0; void setup() { Serial.begin(115200); delay(1000); Serial.println("DIYables Bluetooth - ESP32 BLE Table Example"); // start the BLE server on the ESP32 Uno bluetoothServer.begin(); // register the Table screen with the server bluetoothServer.addApp(&bluetoothTable); // the row names, from top to bottom bluetoothTable.addRow("Temperature"); bluetoothTable.addRow("Humidity"); bluetoothTable.addRow("Pressure"); bluetoothTable.addRow("Counter"); bluetoothTable.addRow("Uptime"); bluetoothTable.addRow("Free Heap"); bluetoothTable.addRow("Status"); Serial.print("Table rows defined: "); Serial.println(bluetoothTable.getRowCount()); // runs when a phone links up or drops the link bluetoothServer.setOnConnected([]() { Serial.println("Bluetooth connected!"); bluetoothTable.sendTableStructure(); updateTableValues(); }); bluetoothServer.setOnDisconnected([]() { Serial.println("Bluetooth disconnected!"); }); // the app asks for the rows again, so send names and values bluetoothTable.onDataRequest([]() { Serial.println("App requested table data"); bluetoothTable.sendTableStructure(); updateTableValues(); }); Serial.println("Waiting for Bluetooth connection..."); } // fills every row with a new value void updateTableValues() { float temperature = 20.0 + random(0, 100) / 10.0; bluetoothTable.sendValueUpdate("Temperature", String(temperature, 1) + " °C"); int humidity = 40 + random(0, 21); bluetoothTable.sendValueUpdate("Humidity", String(humidity) + " %"); int pressure = 1000 + random(0, 21); bluetoothTable.sendValueUpdate("Pressure", String(pressure) + " hPa"); bluetoothTable.sendValueUpdate("Counter", String(counter)); counter++; unsigned long uptime = millis() / 1000; String uptimeStr = String(uptime / 3600) + "h " + String((uptime % 3600) / 60) + "m " + String(uptime % 60) + "s"; bluetoothTable.sendValueUpdate("Uptime", uptimeStr); bluetoothTable.sendValueUpdate("Free Heap", String(ESP.getFreeHeap()) + " bytes"); bluetoothTable.sendValueUpdate("Status", counter % 2 == 0 ? "Running" : "Active"); Serial.println("Table values updated"); } void loop() { bluetoothServer.loop(); if (bluetooth.isConnected() && millis() - lastUpdate >= UPDATE_INTERVAL) { lastUpdate = millis(); updateTableValues(); } delay(10); }

Upload it with the Upload button.
Read 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 Table Example Table rows defined: 7 Waiting for Bluetooth connection...

Ln 11, Col 1

ESP32 Dev Module on COM15

Pro tip: rename DEVICE_NAME (for example to "Garage_Table") when two boards run the same sketch in one room. Then you always tap the right board in the scan list.

Step 3 — Link the Phone App

At the end of this step, the rows appear on your phone and keep changing.

Get the app: DIYables Bluetooth App for Android or iOS.
Classic sketch only — pair first: on the Android phone open Settings > Bluetooth, switch Bluetooth on, tap "ESP32_Table", accept the request (no PIN), and wait until it says "Paired". With the BLE sketch, skip this step.
Launch the app and grant the access it asks for on first start:

Nearby Devices (Android 12 or newer) or Bluetooth (iOS) — lets the app find and link devices
Location (Android 11 or older) — older Android needs it for BLE scans

Make sure phone Bluetooth is on.

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

DIYables Bluetooth App - Home Screen with Scan Button

Pick your board: "ESP32_Table" for Classic, or "ESP32BLE_Table" for BLE. Once linked, the app jumps back to the home screen.
Open the list view: tap Table in the app menu.

DIYables Bluetooth App - Home Screen with Table App

Check the rows: names on the left, values on the right, all refreshed once per second.

Pro tip: the gear icon on the home screen hides the screens you do not use. Every screen is described in the DIYables Bluetooth App User Manual.

Switch back to the Serial Monitor. The link and each refresh now show up:

Newbiely | Arduino IDE 2.3.8

──

☐

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! Table values updated Table values updated App requested table data Table values updated Table values updated Bluetooth disconnected!

Ln 11, Col 1

ESP32 Dev Module on COM15

Video Tutorial

See the ESP32 Uno build in action in the video below. The demo sketch reads a real DHT11 on D3 (GPIO25) and switches an external LED on D13 (GPIO18) every 3 seconds, and both show up as rows next to the test values. The DHT11 code needs one more library: add Adafruit's "DHT sensor library" through Library Manager first.

/* * 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-table */ /* * DIYables Bluetooth Library - ESP32 Uno BLE Table video demo * Shows rows of data in the DIYables Bluetooth STEM app on Android phones and iPhones * * What this demo adds to the plain table sketch: * - real temperature and humidity from a DHT11 module on D3 (GPIO25) * - an external LED on D13 (GPIO18) that turns on and off every 3 seconds * - the LED state shown in its own row * * Board: ESP32 Uno form board (Arduino IDE board "ESP32 Dev Module") * * Tip: pick Tools > Partition Scheme > "Huge APP (3MB No OTA/1MB SPIFFS)" * because the Bluetooth code is too big for the default partition * * How to try it: * 1. Upload this sketch to the ESP32 Uno * 2. Open the Serial Monitor at 115200 baud to follow the link state * 3. Connect with the DIYables Bluetooth App and open the Table screen * * Tutorial: https://diyables.io/bluetooth-app * Author: DIYables */ #include <DIYables_BluetoothServer.h> #include <DIYables_BluetoothTable.h> #include <platforms/DIYables_Esp32BLE.h> #include <DHT.h> // BLE name and UUIDs that the app looks for const char* DEVICE_NAME = "ESP32BLE_Table"; 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 on top of it DIYables_Esp32BLE bluetooth(DEVICE_NAME, SERVICE_UUID, TX_UUID, RX_UUID); DIYables_BluetoothServer bluetoothServer(bluetooth); // the Table screen of the app DIYables_BluetoothTable bluetoothTable; #define LED_PIN 18 // D13 (GPIO18) drives the external LED, the board has no built-in LED here #define DHTPIN 25 // D3 (GPIO25) reads the DHT11 DATA pin #define DHTTYPE DHT11 DHT dht(DHTPIN, DHTTYPE); // timer, LED state and counter for the demo unsigned long lastUpdate = 0; const unsigned long UPDATE_INTERVAL = 1000; bool ledState = false; int counter = 0; void setup() { Serial.begin(115200); delay(1000); Serial.println("DIYables Bluetooth - ESP32 BLE Table Example"); // the LED pin is an output pinMode(LED_PIN, OUTPUT); dht.begin(); // start the BLE server on the ESP32 Uno bluetoothServer.begin(); // register the Table screen with the server bluetoothServer.addApp(&bluetoothTable); // the row names, from top to bottom bluetoothTable.addRow("Temperature"); bluetoothTable.addRow("Humidity"); bluetoothTable.addRow("LED Status"); bluetoothTable.addRow("Pressure"); bluetoothTable.addRow("Counter"); bluetoothTable.addRow("Uptime"); bluetoothTable.addRow("Free Heap"); bluetoothTable.addRow("Status"); Serial.print("Table rows defined: "); Serial.println(bluetoothTable.getRowCount()); // runs when a phone links up or drops the link bluetoothServer.setOnConnected([]() { Serial.println("Bluetooth connected!"); bluetoothTable.sendTableStructure(); updateTableValues(); }); bluetoothServer.setOnDisconnected([]() { Serial.println("Bluetooth disconnected!"); }); // the app asks for the rows again, so send names and values bluetoothTable.onDataRequest([]() { Serial.println("App requested table data"); bluetoothTable.sendTableStructure(); updateTableValues(); }); Serial.println("Waiting for Bluetooth connection..."); } // fills every row with a new value void updateTableValues() { //float temperature = 20.0 + random(0, 100) / 10.0; float temperature = dht.readTemperature(); bluetoothTable.sendValueUpdate("Temperature", String(temperature, 1) + " °C"); //int humidity = 40 + random(0, 21); int humidity = dht.readHumidity(); bluetoothTable.sendValueUpdate("Humidity", String(humidity) + " %"); // stop here when the DHT11 gave no valid reading, the next update tries again if (isnan(humidity) || isnan(temperature)) { Serial.println(F("Failed to read from DHT sensor!")); return; } int pressure = 1000 + random(0, 21); bluetoothTable.sendValueUpdate("Pressure", String(pressure) + " hPa"); bluetoothTable.sendValueUpdate("Counter", String(counter)); counter++; unsigned long uptime = millis() / 1000; String uptimeStr = String(uptime / 3600) + "h " + String((uptime % 3600) / 60) + "m " + String(uptime % 60) + "s"; bluetoothTable.sendValueUpdate("Uptime", uptimeStr); bluetoothTable.sendValueUpdate("Free Heap", String(ESP.getFreeHeap()) + " bytes"); bluetoothTable.sendValueUpdate("Status", counter % 2 == 0 ? "Running" : "Active"); Serial.println("Table values updated"); } void loop() { bluetoothServer.loop(); if (bluetooth.isConnected() && millis() - lastUpdate >= UPDATE_INTERVAL) { lastUpdate = millis(); updateTableValues(); } // switch the LED every 3 seconds static unsigned long lastLedToggle = 0; if (millis() - lastLedToggle > 3000) { ledState = !ledState; digitalWrite(LED_PIN, ledState); // show the new LED state in its row bluetoothTable.sendValueUpdate("LED Status", ledState ? "ON" : "OFF"); lastLedToggle = millis(); } delay(10); }

How the Sketch Works

This table maps each block of the ESP32 Uno sketch to its job.

Code Part	What It Does
DIYables_Esp32BLE or DIYables_Esp32Bluetooth	Starts the radio under the name the phone sees
addRow() calls in setup()	Create the labels, top to bottom, up to 20
setOnConnected()	Sends the row names and a first set of values as soon as a phone links
onDataRequest()	Sends names and values again when the app asks for them
updateTableValues()	Builds each value as text and pushes it with sendValueUpdate()
loop() with UPDATE_INTERVAL	Refreshes every row once per second, only while a phone is linked

So the phone never shows an empty list, and no data goes out when nobody is listening.

ESP32 Uno vs UNO R4 for This Project

Moving the table from the UNO R4 WiFi to the ESP32 Uno swaps the radio layer and a few IDE 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
Memory row	Simulated Free Memory	Real Free Heap from ESP.getFreeHeap()
Demo pins	DHT11 on D3 and the built-in LED	DHT11 on D3 (GPIO25) and an external LED on D13 (GPIO18)
Serial speed	9600 baud	115200 baud
Arduino IDE board	Arduino UNO R4 WiFi	ESP32 Dev Module with Huge APP partition

The DHT11 stays on D3, so the demo wiring is the same. Run the DHT11 from 3.3V and add an LED with a resistor on D13, since there is no on-board LED to blink.

Shape the Table for Your Project

After this part, the rows show your own data instead of test numbers. Three calls do most of the work: addRow(), sendValueUpdate() and sendTableStructure().

Create the Rows

Call these in setup(). You can read the row count and any row name back later.

// Add rows during setup bluetoothTable.addRow("Temperature"); bluetoothTable.addRow("Humidity"); bluetoothTable.addRow("Pressure"); bluetoothTable.addRow("Status"); bluetoothTable.addRow("Uptime"); // Check row count int rows = bluetoothTable.getRowCount(); Serial.println("Total rows: " + String(rows)); // Get attribute name by index String attr = bluetoothTable.getAttribute(0); // Returns "Temperature"

Change a Value

Point at a row by its label or by its position. Positions count from 0.

// Update by attribute name bluetoothTable.sendValueUpdate("Temperature", "25.3 °C"); bluetoothTable.sendValueUpdate("Humidity", "62%"); bluetoothTable.sendValueUpdate("Status", "Running"); // Update by row index (0-based) bluetoothTable.sendValueUpdate(0, "25.3 °C"); // First row bluetoothTable.sendValueUpdate(1, "62%"); // Second row

Reply When the App Asks

The app asks for the layout on connect and on refresh. Send the names first, then the values.

bluetoothTable.onDataRequest([]() { Serial.println("App requested table data"); bluetoothTable.sendTableStructure(); // Send row names // Send current values for all rows bluetoothTable.sendValueUpdate("Temperature", String(temperature, 1) + " °C"); bluetoothTable.sendValueUpdate("Humidity", String(humidity) + "%"); bluetoothTable.sendValueUpdate("Status", "Online"); });

Wipe and Rebuild the Rows

Use this when your project switches mode and needs other labels. Push the new layout right after.

// Clear all rows bluetoothTable.clearTable(); // Add new rows bluetoothTable.addRow("Sensor A"); bluetoothTable.addRow("Sensor B"); // Send updated structure to app bluetoothTable.sendTableStructure();

Know When the Phone Comes and Goes

These hooks are the right spot for a log line, or for pausing work while no phone is linked.

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

Reading the Table Screen

Know the two columns and the limits, and you can plan labels that fit a phone.

Screen Part	Meaning
Left column	The labels you made with addRow()
Right column	The latest text sent with sendValueUpdate()
Refresh	A cell changes the moment new text arrives, with no button press
Row limit	20 rows at most (MAX_TABLE_ROWS = 20)
Value type	Everything is shown as text, so add units yourself

Short labels such as "Temp" or "RH" leave more room for the value on small screens.

Code Recipes

Each recipe shows only the lines that change. Keep the Bluetooth setup from the full sketch. Wires go to Uno header labels, while the code holds the matching GPIO numbers.

Recipe 1 — Five-Sensor Dashboard

Five rows refresh every 2 seconds. A light sensor sits on A3 (GPIO34) and an air quality sensor on A2 (GPIO35). readTemperature(), readHumidity() and readPressure() stand for your own sensor functions.

void setup() { Serial.begin(115200); // set the ADC attenuation to 11 dB (up to ~3.3V input) analogSetAttenuation(ADC_11db); // ... Bluetooth setup from the full sketch ... // rows for the dashboard bluetoothTable.addRow("Temperature"); bluetoothTable.addRow("Humidity"); bluetoothTable.addRow("Pressure"); bluetoothTable.addRow("Light Level"); bluetoothTable.addRow("Air Quality"); } void loop() { bluetoothServer.loop(); static unsigned long lastUpdate = 0; if (millis() - lastUpdate >= 2000) { lastUpdate = millis(); float temp = readTemperature(); float hum = readHumidity(); float press = readPressure(); int light = analogRead(34); // A3 (GPIO34) light sensor int airQuality = analogRead(35); // A2 (GPIO35) air quality sensor bluetoothTable.sendValueUpdate("Temperature", String(temp, 1) + " °C"); bluetoothTable.sendValueUpdate("Humidity", String(hum, 0) + "%"); bluetoothTable.sendValueUpdate("Pressure", String(press, 0) + " hPa"); bluetoothTable.sendValueUpdate("Light Level", String(map(light, 0, 4095, 0, 100)) + "%"); bluetoothTable.sendValueUpdate("Air Quality", airQuality < 1000 ? "Good" : "Poor"); } delay(10); }

Good to know: analogSetAttenuation(ADC_11db) lets the ESP32 Uno analog pin read the full span, from 0V up to about 3.3V. Without a wide range, readings hit 4095 too early and the light and air values look wrong.

Recipe 2 — Board Health Panel

The board reports on itself: run time, free heap and chip temperature from temperatureRead().

bluetoothTable.addRow("Uptime"); bluetoothTable.addRow("Free Heap"); bluetoothTable.addRow("CPU Temp"); bluetoothTable.addRow("WiFi Signal"); bluetoothTable.addRow("Clients"); bluetoothTable.addRow("Status"); void updateSystemStatus() { unsigned long uptime = millis() / 1000; int hours = uptime / 3600; int minutes = (uptime % 3600) / 60; int seconds = uptime % 60; bluetoothTable.sendValueUpdate("Uptime", String(hours) + "h " + String(minutes) + "m " + String(seconds) + "s"); bluetoothTable.sendValueUpdate("Free Heap", String(ESP.getFreeHeap()) + " bytes"); bluetoothTable.sendValueUpdate("CPU Temp", String(temperatureRead(), 1) + " °C"); bluetoothTable.sendValueUpdate("Status", "Online"); }

Good to know: the chip temperature runs well above room temperature and drifts a lot. Treat it as a rough trend, not a thermometer.

Recipe 3 — Input Pin Watcher

One row per pin shows HIGH or LOW once a second. It watches seven Uno header pins: D2, D3, D4, D5, D6, D7 and D9. D8 and D10 are left out on purpose, because they are boot strapping pins.

// D2, D3, D4, D5, D6, D7, D9 on the ESP32 Uno const int PINS[] = {26, 25, 17, 16, 27, 14, 13}; const int NUM_PINS = sizeof(PINS) / sizeof(PINS[0]); void setup() { // ... Bluetooth setup ... for (int i = 0; i < NUM_PINS; i++) { pinMode(PINS[i], INPUT); bluetoothTable.addRow("GPIO " + String(PINS[i])); } } void loop() { bluetoothServer.loop(); static unsigned long lastUpdate = 0; if (millis() - lastUpdate >= 1000) { lastUpdate = millis(); for (int i = 0; i < NUM_PINS; i++) { int state = digitalRead(PINS[i]); bluetoothTable.sendValueUpdate("GPIO " + String(PINS[i]), state == HIGH ? "HIGH" : "LOW"); } } delay(10); }

An unconnected pin floats and flickers between HIGH and LOW. Switch to INPUT_PULLUP when you wire buttons or switches to these pins.

Recipe 4 — Analog Sensor List

A struct keeps name, pin, unit and scale together, so one new line adds one new sensor. The four inputs are A2 to A5 (GPIO35, GPIO34, GPIO36, GPIO39). These are input-only pins on the ESP32 Uno, which suits analog sensors well. The scale numbers are placeholders; set them for your sensors and the 0 to 4095 range.

struct SensorConfig { String name; int pin; String unit; float scale; }; SensorConfig sensors[] = { {"Temperature", 35, "°C", 0.0488}, // A2 (GPIO35) {"Humidity", 34, "%", 0.0244}, // A3 (GPIO34) {"Light", 36, "lux", 0.244}, // A4 (GPIO36) {"Pressure", 39, "hPa", 0.488} // A5 (GPIO39) }; const int NUM_SENSORS = sizeof(sensors) / sizeof(sensors[0]); void setup() { Serial.begin(115200); // set the ADC attenuation to 11 dB (up to ~3.3V input) analogSetAttenuation(ADC_11db); // ... Bluetooth setup ... for (int i = 0; i < NUM_SENSORS; i++) { bluetoothTable.addRow(sensors[i].name); } } void loop() { bluetoothServer.loop(); static unsigned long lastUpdate = 0; if (millis() - lastUpdate >= 2000) { lastUpdate = millis(); for (int i = 0; i < NUM_SENSORS; i++) { int raw = analogRead(sensors[i].pin); float value = raw * sensors[i].scale; bluetoothTable.sendValueUpdate(sensors[i].name, String(value, 1) + " " + sensors[i].unit); } } delay(10); }

A2 to A5 take 3.3V at most. Never feed them a sensor output that can reach 5V. Run the sensor from 3.3V or put a resistor divider in front of the pin.

Smarter Values

A bare number is hard to read in a long list. These two tricks make rows clearer and cut BLE traffic.

Add a Symbol and a Word

The app prints any text, emojis included. The temperature row then says at a glance whether it is cold, fine or hot.

void updateTemperatureRow(float temp) { String status; if (temp < 10) { status = "❄️ " + String(temp, 1) + " °C (Cold)"; } else if (temp < 30) { status = "✅ " + String(temp, 1) + " °C (Normal)"; } else { status = "🔥 " + String(temp, 1) + " °C (Hot!)"; } bluetoothTable.sendValueUpdate("Temperature", status); }

Send Only on Change

No timer here: a new value goes out only when the temperature moves by 0.5 °C or more. getTimestamp() is a function you write.

float lastTemp = 0; float threshold = 0.5; // Only update on significant change void loop() { bluetoothServer.loop(); float temp = readTemperature(); if (abs(temp - lastTemp) >= threshold) { lastTemp = temp; bluetoothTable.sendValueUpdate("Temperature", String(temp, 1) + " °C"); bluetoothTable.sendValueUpdate("Last Change", getTimestamp()); } delay(100); }

Real Hardware to Feed the Table

Idea	What to Connect on the ESP32 Uno
BME280 weather rows	BME280 on SDA (GPIO21) and SCL (GPIO22), one row each for temperature, humidity and pressure
Multi-sensor panel	DHT22, BMP280, LDR and MQ-135, each in its own row, all signals at 3.3V or less
Board info card	Nothing to wire, list the chip type, MAC, heap left, flash size and run time

Good to know: on the ESP32 Uno, A4 and A5 are not I2C. Wire every I2C module to the SDA and SCL header pins.

BLE or Classic Bluetooth on the ESP32 Uno?

The ESP32 Uno runs both sketches. Pick with this table.

Point	BLE sketch (Esp32BLE_Table)	Classic sketch (Esp32Bluetooth_Table)
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_Table	ESP32_Table
Rows in the example	7	8 (adds CPU Freq)

Table values are short text, so BLE is fast enough and covers every phone. It is the safer default.

Debug Helper

When rows look wrong, dump what the board stores to the Serial Monitor. Compare it with the phone to see which side has the problem.

void debugTable() { Serial.println("=== Table Debug ==="); Serial.println("Row Count: " + String(bluetoothTable.getRowCount())); for (int i = 0; i < bluetoothTable.getRowCount(); i++) { Serial.println("Row " + String(i) + ": " + bluetoothTable.getAttribute(i)); } Serial.println("==================="); }

Build Ideas

Area	Table Projects
Monitoring	Weather box, plant care panel with soil moisture and light, aquarium with temperature, pH and TDS
Board diagnostics	Free memory tracker, WiFi details, battery level, chip info
Data logging	Min, max and average of one sensor, event counter, response times, pin state summary
Home	Temperature per room, door and window states, energy use, alarm sensor status

Pair the Table with More App Screens

One Bluetooth server on the ESP32 Uno can host several app screens side by side.

Table Plus Plotter

The table holds the latest number, and the plotter draws its history.

float temperature = 0; void loop() { bluetoothServer.loop(); static unsigned long lastUpdate = 0; if (millis() - lastUpdate >= 2000) { lastUpdate = millis(); temperature = readTemperature(); // Update table bluetoothTable.sendValueUpdate("Temperature", String(temperature, 1) + " °C"); bluetoothTable.sendValueUpdate("Status", temperature > 30 ? "Warning" : "Normal"); // Plot trend bluetoothPlotter.send(temperature); } delay(10); }

Table Plus Monitor

Rows keep the fixed values, and the monitor collects log lines and alerts.

bluetoothTable.sendValueUpdate("Temperature", String(temp, 1) + " °C"); bluetoothMonitor.send("[INFO] Temperature: " + String(temp, 1) + " °C"); if (temp > 40) { bluetoothTable.sendValueUpdate("Status", "ALERT"); bluetoothMonitor.send("[ALERT] High temperature detected!"); }

Try These Next

With the table running, build on it with these ESP32 Uno pages:

ESP32 Uno - Bluetooth Monitor — free text logging
ESP32 Uno - Bluetooth Plotter — live graphs of your data
ESP32 Uno - Bluetooth Temperature — a thermometer-style screen
ESP32 Uno - Multiple Bluetooth Apps — the table next to other screens

Where to Get Help

The API reference that ships 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
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)
ESP32_Table is not listed on an iPhone	iOS has no Classic Bluetooth	Upload the BLE sketch and tap ESP32BLE_Table
Board name is missing from the scan	Sketch not running, phone Bluetooth off, or Classic not paired	Look for "Waiting for Bluetooth connection..." in the Serial Monitor, turn on Bluetooth, pair ESP32_Table first for Classic, and enable Location on Android 11 or older
The Table screen stays blank	No rows, or the layout was never sent	Add rows with addRow() in setup() and call sendTableStructure() inside onDataRequest()
One cell never updates	The label in sendValueUpdate() differs from the one in addRow()	Labels are case-sensitive, so copy the exact text or use the row index
More than 20 rows wanted, extra rows missing	The table holds 20 rows at most	Join two values in one row or rebuild the table with clearTable()
Temperature row reads nan in the video demo	DHT11 not answering	Verify the DATA wire goes to D3 (GPIO25) with power on 3.3V and a shared GND, and confirm the Adafruit DHT library is installed
Garbled symbols scroll in the Serial Monitor	Speed mismatch	Pick 115200 in the baud menu at the bottom right

FAQ

Do I need to pair the ESP32 Uno before opening the table app?

Only with the Classic Bluetooth sketch. Pair "ESP32_Table" once in the Android Bluetooth settings, then connect from the app. The BLE sketch needs no pairing; you just scan inside the app and tap "ESP32BLE_Table".

How many values can one Bluetooth table hold?

Twenty rows. For more, put two readings in one cell, such as "24.6 °C / 51%", or switch between two layouts with clearTable() and a new set of addRow() calls.

Can a row show text instead of a number?

Yes. Every value is a string, so you can send words like "Door open", units, symbols or emojis. Build the text with String() and the + operator before you call sendValueUpdate().

Is it better to update a row by its name or by its number?

The name is easier to read and keeps working if you reorder rows. The index (from 0) is shorter and avoids typos. Both send the same data to the app.

How is the ESP32 Uno sketch different from the UNO R4 WiFi table code?

The UNO R4 WiFi uses ArduinoBLE_Table with the ArduinoBLE platform file and 9600 baud. The ESP32 Uno uses Esp32BLE_Table or Esp32Bluetooth_Table, prints at 115200 baud, needs the Huge APP partition, and reports real free heap with ESP.getFreeHeap() instead of a made-up memory number.

Why does the analog recipe call analogSetAttenuation(ADC_11db)?

It opens the ESP32 Uno ADC to about 0 to 3.3V, so a sensor swinging over that span fills the whole 0 to 4095 scale. Without it, the reading reaches 4095 far below 3.3V and the row shows a maxed-out value. UNO R4 code never needed this line; only the ESP32 Uno side uses it. Keep the sensor signal at 3.3V or lower.

Can I wire a button with INPUT_PULLUP to A2 to A5 for the pin watcher?

Not without help. A2 to A5 (GPIO35, 34, 36, 39) are input only and have no internal pull-up or pull-down. Add a 10kΩ resistor to 3.3V, or use the digital pins D2 to D7 and D9, which do have internal pull-ups.

Will analogRead() still work on A0 and A1 if I add WiFi later?

No. A0 (GPIO2) and A1 (GPIO4) are ADC2 pins, and ADC2 cannot be read while WiFi is on. With Bluetooth alone they read fine. For a project that also uses WiFi, put analog sensors on A2 to A5 or GPIO32/33, as the recipes on this page already do.

Do I need a driver to upload to the ESP32 Uno?

The board talks to the computer through a CH340 USB-to-serial chip. Windows and macOS may need the CH340 driver before a COM port appears. Install it once, then plug the cable in again.

What if my project 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 keep reading while WiFi is on) and GPIO15 (I/O, PWM, analog on ADC2). Solder pin headers into them and use the GPIO number in code. For one or two more analog rows in your table, GPIO32 and GPIO33 are the best fit. Two warnings: 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. Also 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 show the same table in a web browser?

Yes. The ESP32 Uno also has WiFi. The ESP32 Uno - Web Table page builds the same kind of row list on a web page that any phone or PC on your network can open.

Learn More

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