ESP32 NRF24L01+ Chat Device

A project by RDH Robotics

This project implements a two-way chat system using ESP32 microcontrollers, NRF24L01+ transceivers, and TFT displays with a custom button-based keyboard interface. Two device-specific Arduino sketches (Device1_Chat.ino and Device2_Chat.ino) enable communication between two devices over a 2.4GHz wireless link. Users can input messages via a 5x5 keyboard displayed on a TFT screen or through a Serial terminal, with support for letters, numbers, punctuation, and emojis. Received messages are stored and displayed, with robust error handling for stable communication.

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🚀 Features

• Wireless Communication: Uses NRF24L01+ modules for reliable 2.4GHz communication.
• TFT Interface: Displays a 5x5 keyboard, recipient code, current message, and up to 5 received messages.
• Button Controls: Navigate and type using analog buttons (UP, DOWN, LEFT, RIGHT, MIDDLE, PAGE, EMOJI).
• Serial Interface: Send messages, set recipient codes, and control ADC debugging via Serial commands.
• Message History: Stores and displays up to 5 received messages in smaller text.
• Stable Transmission: Configured with retries and low power settings for reliable communication.
• Dynamic Recipient Codes: Set 4-digit recipient codes via Serial or buttons.

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🧰 Hardware Requirements

• 2x ESP32 Development Boards (e.g., ESP32-WROOM-32)
• 2x NRF24L01+ Transceivers
• 2x TFT Displays (compatible with TFT_eSPI, e.g., 240x320 ILI9341)
• Analog Button Circuit connected to ADC pin (GPIO36/VP)
  • Voltage Thresholds:
    • UP: 1.5V
    • DOWN: 0.6V
    • LEFT: 1.0V
    • RIGHT: 0.15V
    • MIDDLE: 0V
    • PAGE: 0.3V
    • EMOJI: 0.11V

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🔌 Wiring

NRF24L01+

NRF24L01+	ESP32 GPIO
CE	GPIO5
CSN	GPIO17
SCK	GPIO18
MOSI	GPIO23
MISO	GPIO19

TFT Display

Configured via TFT_eSPI's User_Setup.h file.

Buttons

All buttons connected to GPIO36 (VP) using a resistor divider network.

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🖥️ Software Requirements

• Arduino IDE
• Libraries:
  • SPI.h
  • RF24.h (NRF24L01+ driver)
  • TFT_eSPI.h (TFT display driver)

Note: Ensure User_Setup.h is configured properly for your display.

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⚙️ Setup Instructions

Hardware

1. Connect NRF24L01+ to each ESP32.
2. Wire TFT display and configure User_Setup.h.
3. Connect analog buttons to GPIO36 using a voltage divider.
4. Add a capacitor (e.g., 10µF) across NRF24L01+'s VCC/GND for stability.

Software

1. Install required libraries via Arduino Library Manager.
2. Update User_Setup.h in the TFT_eSPI library.
3. Upload Device1_Chat.ino to Device 1 (MY_CODE = 1234).
4. Upload Device2_Chat.ino to Device 2 (MY_CODE = 5678).
5. Open Serial Monitor at 115200 baud with Newline enabled.

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🕹️ Usage Guide

Modes

1. Recipient Selection Mode (mode = 0)

• UP/DOWN: Change digit
• LEFT/RIGHT: Move between digits
• MIDDLE: Confirm code & switch to typing

2. Typing Mode (mode = 1)

• Navigate the 5x5 keyboard using direction buttons.
• MIDDLE: Select character / Backspace (<)
• PAGE: Switch keyboard pages (Letters / Numbers / Emojis)
• UP + DOWN (together): Quick jump to Emoji page
• Long press MIDDLE: Send message (shows "Sent")

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🖼️ Display Layout

Element	Position (Y)	Text Size	Notes
Instructions	0	1	Button guide
Recipient Code	20	3	Highlights current digit (mode 0)
Current Message	60	2	What you're typing
Received Messages	90–165	1	Up to 5 messages, shown in yellow
"Sent" Indicator	220	2	Visible for 2 seconds after sending
Keyboard	245–320	1	Selected character in green

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🧑‍💻 Serial Commands

Command	Description
set XXXX	Set recipient code (e.g., set 5678)
chng XXXX	Change recipient code (no mode reset)
<message>	Send message directly
ADCprint	Enable ADC value monitoring
ADCstop	Disable ADC value monitoring

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📡 Example Chat

1. On Device 1, enter set 5678
2. On Device 2, enter set 1234
3. Type and send a message from Serial or TFT
4. Messages appear on TFT and Serial Monitor

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🧠 Code Structure

• Device1_Chat.ino → MY_CODE = 1234, default recipient 5678
• Device2_Chat.ino → MY_CODE = 5678, default recipient 1234

Key Functions

Function	Description
setup()	Initializes Serial, TFT, SPI, RF24, ADC
loop()	Main logic, handles input and message handling
readButton()	Reads ADC pin and determines which button was pressed
handleButton()	Executes button actions
updateDisplay()	Renders the full screen UI

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🛠️ Troubleshooting

No Communication?

• Check NRF24L01+ wiring and stable 3.3V power (add capacitor)
• Verify correct recipient codes and Serial Monitor settings

TFT Display Blank?

• Ensure User_Setup.h is properly configured
• Double check all SPI connections

Button Not Working?

• Use ADCprint to verify voltage levels
• Adjust resistors if thresholds are mismatched

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📜 License

This project is licensed under the MIT License.

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🤝 Contributing

PRs and ideas welcome!
Open an issue or submit a pull request on GitHub.

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🧠 Built with ❤️ by RDH Robotics

Powered by the Arduino Ecosystem, ESP32, NRF24L01+, and the amazing RF24 and TFT_eSPI libraries.