Arduino Nano ESP32 - DIYables Bluetooth App Digital Pins
Overview
This example provides remote GPIO pin control and monitoring on the Arduino Nano ESP32 using BLE (Bluetooth Low Energy) via the DIYables Bluetooth STEM app. Control output pins and monitor input pins wirelessly from a smartphone. Suitable for relay control, button monitoring, LED switching, and any application requiring remote pin access.
Note: The Arduino Nano ESP32 supports BLE only — Classic Bluetooth is not supported. The DIYables Bluetooth App works on both Android and iOS with BLE.
Features
- Output Control: Set digital pins HIGH or LOW remotely
- Input Monitoring: Read digital and analog pin states
- Named Pins: Assign descriptive labels to each pin (e.g., "LED", "Relay")
- Real-Time Updates: Push pin state changes to the app
- Up to 16 Pins: Control multiple pins simultaneously
- Android & iOS Support: BLE is compatible with both platforms
- No Pairing Required: BLE connects without manual pairing
Hardware Preparation
Or you can buy the following 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 .
Arduino Nano ESP32 Code
Detailed Instructions
- New to the Arduino Nano ESP32? Start with the Arduino Nano ESP32 getting started guide.
- Connect the Arduino Nano ESP32 to your computer via USB.
- Open Arduino IDE.
- Select the Arduino Nano ESP32 board and the correct COM port.
- Click the Libraries icon in the left sidebar.
- Search for "DIYables Bluetooth" and select the DIYables Bluetooth library by DIYables.
- Click Install.
- When prompted to install dependencies, click Install All.
BLE Code
- In Arduino IDE, open File Examples DIYables Bluetooth ArduinoBLE_PinControl, or paste the code into the editor.
/*
* DIYables Bluetooth Library - ESP32 BLE Pin Control/Monitor Example
* Works with DIYables Bluetooth STEM app on Android and iOS
*
* This example demonstrates the Bluetooth Pin Control/Monitor feature:
* - Control digital output pins via Bluetooth
* - Monitor digital input pins
* - Monitor analog input pins
* - Configure pin modes (INPUT/OUTPUT)
*
* Tutorial: https://diyables.io/bluetooth-app
* Author: DIYables
*/
#include <DIYables_BluetoothServer.h>
#include <DIYables_BluetoothPinControl.h>
#include <platforms/DIYables_Esp32BLE.h>
// BLE Configuration
const char* DEVICE_NAME = "ESP32BLE_Pins";
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";
// Create Bluetooth instances
DIYables_Esp32BLE bluetooth(DEVICE_NAME, SERVICE_UUID, TX_UUID, RX_UUID);
DIYables_BluetoothServer bluetoothServer(bluetooth);
// Create Pin Control/Monitor app instance
DIYables_BluetoothPinControl bluetoothPins;
// Pin configuration (ESP32 GPIOs)
const int LED_PIN = LED_BUILTIN; // Built-in LED
const int OUTPUT_PIN_1 = D6;
const int OUTPUT_PIN_2 = D7;
const int INPUT_PIN_1 = D4;
const int INPUT_PIN_2 = D5;
const int ANALOG_PIN_1 = A0; // Input-only ADC pin
const int ANALOG_PIN_2 = A1; // Input-only ADC pin
void setup() {
Serial.begin(115200);
delay(1000);
Serial.println("DIYables Bluetooth - ESP32 BLE Pin Control/Monitor Example");
// Initialize pins
pinMode(LED_PIN, OUTPUT);
pinMode(OUTPUT_PIN_1, OUTPUT);
pinMode(OUTPUT_PIN_2, OUTPUT);
pinMode(INPUT_PIN_1, INPUT_PULLUP);
pinMode(INPUT_PIN_2, INPUT_PULLUP);
// Initialize Bluetooth server with platform-specific implementation
bluetoothServer.begin();
// Add digital pins app to server
bluetoothServer.addApp(&bluetoothPins);
// Configure which pins are accessible via Bluetooth with custom names
bluetoothPins.enablePin(LED_PIN, BT_PIN_OUTPUT, "LED");
bluetoothPins.enablePin(OUTPUT_PIN_1, BT_PIN_OUTPUT, "Out1");
bluetoothPins.enablePin(OUTPUT_PIN_2, BT_PIN_OUTPUT, "Out2");
bluetoothPins.enablePin(INPUT_PIN_1, BT_PIN_INPUT, "Btn1");
bluetoothPins.enablePin(INPUT_PIN_2, BT_PIN_INPUT, "Btn2");
bluetoothPins.enablePin(ANALOG_PIN_1, BT_PIN_INPUT, "A34");
bluetoothPins.enablePin(ANALOG_PIN_2, BT_PIN_INPUT, "A35");
// Set up connection event callbacks
bluetoothServer.setOnConnected([]() {
Serial.println("Bluetooth connected!");
});
bluetoothServer.setOnDisconnected([]() {
Serial.println("Bluetooth disconnected!");
});
// Set up callback for pin write commands
bluetoothPins.onPinWrite([](int pin, int state) {
digitalWrite(pin, state);
Serial.print("Pin ");
Serial.print(pin);
Serial.print(" set to ");
Serial.println(state ? "HIGH" : "LOW");
});
// Set up callback for pin read commands
bluetoothPins.onPinRead([](int pin) -> int {
int state;
if (pin == ANALOG_PIN_1 || pin == ANALOG_PIN_2) {
state = analogRead(pin);
Serial.print("Analog pin ");
Serial.print(pin);
Serial.print(" read: ");
Serial.println(state);
} else {
state = digitalRead(pin);
Serial.print("Digital pin ");
Serial.print(pin);
Serial.print(" read: ");
Serial.println(state ? "HIGH" : "LOW");
}
return state;
});
// Set up callback for pin mode changes
bluetoothPins.onPinModeChange([](int pin, int mode) {
pinMode(pin, mode == BT_PIN_OUTPUT ? OUTPUT : INPUT_PULLUP);
Serial.print("Pin ");
Serial.print(pin);
Serial.print(" mode changed to ");
Serial.println(mode == BT_PIN_OUTPUT ? "OUTPUT" : "INPUT");
});
Serial.println("Waiting for Bluetooth connection...");
Serial.print("Enabled pins: ");
Serial.println(bluetoothPins.getEnabledPinCount());
}
void loop() {
bluetoothServer.loop();
static unsigned long lastInputCheck = 0;
static int lastInputState1 = HIGH;
static int lastInputState2 = HIGH;
static int lastAnalogState1 = 0;
static int lastAnalogState2 = 0;
if (millis() - lastInputCheck >= 100) {
lastInputCheck = millis();
int currentState1 = digitalRead(INPUT_PIN_1);
if (currentState1 != lastInputState1) {
lastInputState1 = currentState1;
bluetoothPins.updatePinState(INPUT_PIN_1, currentState1);
Serial.print("Input pin ");
Serial.print(INPUT_PIN_1);
Serial.print(" changed to ");
Serial.println(currentState1 ? "HIGH" : "LOW");
}
int currentState2 = digitalRead(INPUT_PIN_2);
if (currentState2 != lastInputState2) {
lastInputState2 = currentState2;
bluetoothPins.updatePinState(INPUT_PIN_2, currentState2);
Serial.print("Input pin ");
Serial.print(INPUT_PIN_2);
Serial.print(" changed to ");
Serial.println(currentState2 ? "HIGH" : "LOW");
}
// ESP32 has 12-bit ADC (0-4095)
int currentAnalog1 = analogRead(ANALOG_PIN_1);
if (abs(currentAnalog1 - lastAnalogState1) > 40) { // ~1% of 4095
lastAnalogState1 = currentAnalog1;
bluetoothPins.updatePinState(ANALOG_PIN_1, currentAnalog1);
Serial.print("Analog pin ");
Serial.print(ANALOG_PIN_1);
Serial.print(" changed to ");
Serial.println(currentAnalog1);
}
int currentAnalog2 = analogRead(ANALOG_PIN_2);
if (abs(currentAnalog2 - lastAnalogState2) > 40) {
lastAnalogState2 = currentAnalog2;
bluetoothPins.updatePinState(ANALOG_PIN_2, currentAnalog2);
Serial.print("Analog pin ");
Serial.print(ANALOG_PIN_2);
Serial.print(" changed to ");
Serial.println(currentAnalog2);
}
}
delay(10);
}
- Click Upload to flash the sketch to the board.
- Open the Serial Monitor.
- The Serial Monitor output should look like:
COM6
DIYables Bluetooth - Pin Control/Monitor Example
Waiting for Bluetooth connection...
Enabled pins: 7
Autoscroll
Clear output
9600 baud
Newline
Mobile App
Note: The DIYables Bluetooth App works on both Android and iOS with BLE. No manual pairing is required.
- Launch the DIYables Bluetooth App.
- On first launch, grant the following permissions:
- Nearby Devices (Android 12+) / Bluetooth (iOS) — required to scan and connect to Bluetooth devices
- Location (Android 11 and below only) — required by older Android versions to scan for BLE
- Ensure Bluetooth is enabled on your device.
- Tap Connect on the home screen. The app will scan for BLE devices.
- Tap "Arduino_Pins" in the scan results.
- After connecting, return to the home screen and open the Digital Pins app.
Tap the settings icon on the home screen to show or hide apps. See the DIYables Bluetooth App User Manual for details.
- The enabled pins are listed with their names and current states.
- Tap output pins to toggle HIGH/LOW, and observe input pin values update in real time.
Now look back at the Serial Monitor on Arduino IDE. You will see:
COM6
Bluetooth connected!
Pin 13 set to HIGH
Pin 13 set to LOW
Digital pin 7 read: HIGH
Autoscroll
Clear output
9600 baud
Newline
Creative Customization - Adapt the Code to Your Project
Enable Pins
// Enable pins with mode and friendly name
bluetoothPins.enablePin(13, BT_PIN_OUTPUT, "LED");
bluetoothPins.enablePin(12, BT_PIN_OUTPUT, "Relay");
bluetoothPins.enablePin(7, BT_PIN_INPUT, "Button");
bluetoothPins.enablePin(A0, BT_PIN_INPUT, "Sensor");
// Check enabled pin count
int count = bluetoothPins.getEnabledPinCount();
Handle Pin Write/Read/Mode
bluetoothPins.onPinWrite([](int pin, int state) {
digitalWrite(pin, state);
Serial.print("Pin ");
Serial.print(pin);
Serial.println(state ? " ? HIGH" : " ? LOW");
});
bluetoothPins.onPinRead([](int pin) -> int {
if (pin >= A0) {
return analogRead(pin);
}
return digitalRead(pin);
});
bluetoothPins.onPinModeChange([](int pin, int mode) {
pinMode(pin, mode == BT_PIN_OUTPUT ? OUTPUT : INPUT_PULLUP);
});
Push State Changes
// Notify the app when a pin state changes
bluetoothPins.updatePinState(7, digitalRead(7));
bluetoothPins.updatePinState(A0, analogRead(A0));
Programming Examples
Relay Control with Button Monitor
const int RELAY_PIN = 12;
const int BUTTON_PIN = 7;
void setup() {
pinMode(RELAY_PIN, OUTPUT);
pinMode(BUTTON_PIN, INPUT_PULLUP);
bluetoothPins.enablePin(RELAY_PIN, BT_PIN_OUTPUT, "Relay");
bluetoothPins.enablePin(BUTTON_PIN, BT_PIN_INPUT, "Button");
bluetoothPins.onPinWrite([](int pin, int state) {
digitalWrite(pin, state);
});
}
void loop() {
bluetoothServer.loop();
// Monitor button and push changes
static int lastState = HIGH;
int state = digitalRead(BUTTON_PIN);
if (state != lastState) {
lastState = state;
bluetoothPins.updatePinState(BUTTON_PIN, state);
}
delay(10);
}
Multi-LED Controller
const int LED_PINS[] = {8, 9, 10, 11, 12, 13};
const char* LED_NAMES[] = {"Red", "Green", "Blue", "Yellow", "White", "Built-in"};
const int NUM_LEDS = 6;
void setup() {
for (int i = 0; i < NUM_LEDS; i++) {
pinMode(LED_PINS[i], OUTPUT);
bluetoothPins.enablePin(LED_PINS[i], BT_PIN_OUTPUT, LED_NAMES[i]);
}
bluetoothPins.onPinWrite([](int pin, int state) {
digitalWrite(pin, state);
});
}
Troubleshooting
Common Issues
1. Device not visible in the app
- Confirm the board is powered on and the sketch is uploaded
- Verify Bluetooth is enabled on your phone
- On Android 11 and below, enable Location services as well
2. Pin toggle not working
- Confirm the pin is enabled with BT_PIN_OUTPUT mode
- Verify the onPinWrite callback is registered
- Check wiring connections
3. Input pins not updating
- Ensure updatePinState() is called when the pin state changes
- Check the polling frequency in the loop
4. Analog values not showing
- Use analogRead() in the onPinRead callback for analog pins
- Analog pins return values in the 0–1023 range
5. Connection drops frequently
- Reduce distance to the Arduino
- Ensure a stable USB power supply
6. Upload fails or board not recognized
- Install the latest Arduino Nano ESP32 board package via Board Manager
- Try a different USB cable or port
Project Ideas
- Multi-relay control panel
- Button and switch monitor
- LED lighting controller
- Home automation switch panel
- Sensor input dashboard
Next Steps
After completing the Bluetooth Digital Pins example, explore:
- Bluetooth Slider — Analog value control
- Bluetooth Monitor — Text-based status feedback
- Bluetooth Table — Structured pin status display
- Multiple Bluetooth Apps — Combine pin control with other app widgets
Support
For additional help:
- Check the API Reference documentation
- Visit DIYables tutorials
- Arduino community forums