Smart Multi-Protocol ESP32 Transmitter System

Overview

Components Used

• 2 × ESP32 DevKit V1
  • Controller ESP32
  • Dashboard ESP32
• 2 × Analog Joysticks
• 5 × Potentiometers
• 1 × 4×4 Matrix Keypad
• 2 × Push Buttons (UP & DOWN)
• 1 × ST7920 128×64 Graphical LCD
• 1 × NRF24L01+ 2.4 GHz Wireless Transceiver Module
• 1 × MPU6050 6-Axis IMU (Accelerometer + Gyroscope)
• 1 × LM2596 DC-DC Buck Converter Module
• 1 × Dual 18650 Battery Holder (2-Cell)
• 1 × Power Switch
• Custom 2-Layer PCB (Planned) / Perfboard (Current Prototype)

This project is a custom-built ESP32-based Smart Transmitter System designed for robotics, UGVs, AMRs, drones, and future autonomous systems.

The transmitter features:

• Graphical LCD Dashboard
• Multiple Control Inputs
• Real-Time Channel Monitoring
• Multi-Protocol Communication Support
• Professional Menu-Driven User Interface
• Expandable Architecture for Future Robotics Applications

The system is built using two ESP32 microcontrollers:

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System Architecture

Controller ESP32

Responsible for reading all physical user inputs:

• 2 Analog Joysticks
• 5 Potentiometers
• 4×4 Matrix Keypad
• UP Button
• DOWN Button

Dashboard ESP32

Responsible for:

• LCD User Interface
• Menu System
• Settings Management
• Channel Monitoring
• Communication Management
• Protocol Selection
• Wireless Transmission

The Controller ESP32 sends all channel data to the Dashboard ESP32 using UART communication.

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Features

User Interface

Boot Screen

• Startup Animation
• System Initialization

Password System

• Keypad-Based Login
• Secure Transmitter Access

Dashboard

• Mode Display
• Link Status
• Protocol Status
• Battery Indicator
• Signal Animation
• Settings Shortcut

Settings Menu

• Wheel Ratio Configuration
• Channel Monitor
• Protocol Selection

Channel Monitor

Provides real-time monitoring of all transmitter channels.

Protocol Menu

Selectable communication protocols:

• RADIO (NRF24L01)
• ESP-NOW
• WiFi
• Bluetooth

Only one protocol can be active at a time.

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Hardware Configuration

Controller ESP32

Joystick 1

Function	Pin
X Axis	GPIO32
Y Axis	GPIO33
Switch	GPIO18

Joystick 2

Function	Pin
X Axis	GPIO34
Y Axis	GPIO35
Switch	GPIO19

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Potentiometers

Channel	Pin
POT1	GPIO39
POT2	GPIO25
POT3	GPIO26
POT4	GPIO27
POT5	GPIO14

Each potentiometer: outer pins to 3.3V and GND, middle pin to ESP32 GPIO.

Buttons

Button	Pin
UP	GPIO21
DOWN	GPIO23

Each button : another pin to be connected with 3.3V pin of esp32.

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Keypad

Row Pins

Row	GPIO
R1	4
R2	5
R3	12
R4	13

Column Pins

Column	GPIO
C1	2
C2	15
C3	22
C4	3

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Dashboard ESP32

LCD

Display Type

ST7920 128×64 Graphical LCD

Connections

LCD Pin	ESP32 Pin
RS	GPIO5
RW	GPIO23
E	GPIO18
RST	GPIO4
PSB	GND
VCC	5V
GND	GND
BLA	Potentiometer (Middle Pin + GND Pin Short)
BLK	GND

Library

U8G2

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MPU6050

Dashboard ESP32 Connections

MPU6050 Pin	ESP32 Pin
VCC	3.3V
GND	GND
SDA	GPIO21
SCL	GPIO22

Purpose

The MPU6050 is reserved for future expansion and will be used for:

• Gesture-Based Robot Control
• Motion Sensing
• Tilt-Based Driving
• Orientation Detection
• Robotic Arm Control
• Drone Attitude Commands
• Human-Machine Interaction

Communication Between ESP32 Boards

UART2

Controller ESP32

Function	GPIO
TX	GPIO17
RX	GPIO16

Dashboard ESP32

Function	GPIO
TX	GPIO17
RX	GPIO16

Baud Rate

115200

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Channel Mapping

Channel	Source
CH1	Joystick 1 X
CH2	Joystick 1 Y
CH3	Joystick 2 X
CH4	Joystick 2 Y
CH5	Joystick 1 Button
CH6	Joystick 2 Button
CH7	Potentiometer 1
CH8	Potentiometer 2
CH9	Potentiometer 3
CH10	Potentiometer 4
CH11	Potentiometer 5

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Communication Protocols

RADIO

Hardware

NRF24L01

Status

Implemented Framework

Future

Primary Low-Latency Control Protocol

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ESP-NOW

Hardware

Built-in ESP32 WiFi Radio

Status

Implemented Framework

Future

Medium-Range Low-Latency Communication

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WiFi

Hardware

Built-in ESP32 WiFi

Status

Implemented Framework

Future

UDP Communication & Telemetry

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Bluetooth

Hardware

Built-in ESP32 Bluetooth

Status

Implemented Framework

Future

Mobile App Connectivity & Debugging

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NRF24L01 Connections

Dashboard ESP32

NRF24 Pin	ESP32 Pin
VCC	3.3V
GND	GND
CE	GPIO27
CSN	GPIO26
SCK	GPIO14
MOSI	GPIO13
MISO	GPIO12

Important: Place a 10µF capacitor between VCC and GND close to the NRF24L01 module.

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Protocol Architecture

Only one communication protocol is active at any given time.

Example: RADIO Selected

• NRF24 Enabled
• ESP-NOW Disabled
• WiFi Disabled
• Bluetooth Disabled

Example: ESP-NOW Selected

• NRF24 Disabled
• ESP-NOW Enabled
• WiFi Disabled
• Bluetooth Disabled

Benefits

• Reduced Memory Usage
• Lower CPU Load
• Improved Reliability
• Reduced Power Consumption

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Data Packet Structure

struct ControlPacket
{
    int ch1;
    int ch2;
    int ch3;
    int ch4;

    int ch5;
    int ch6;

    int ch7;
    int ch8;
    int ch9;
    int ch10;
    int ch11;
};

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Current Project Status

Completed

• ESP32 Controller
• ESP32 Dashboard
• UART Communication
• Graphical LCD Interface
• Password System
• Dashboard UI
• Settings Menu
• Channel Monitor
• Protocol Menu
• Single Protocol Selection Logic
• NRF24 Framework
• ESP-NOW Framework
• WiFi Framework
• Bluetooth Framework

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Future Development

• NRF24L01 Receiver
• Bidirectional Telemetry
• Robot Receiver Firmware
• WiFi Telemetry Dashboard
• Bluetooth Mobile Application
• LoRa Integration
• OTA Updates
• Battery Monitoring
• SD Card Logging

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Circuit Link

https://app.cirkitdesigner.com/project/51af68e7-1b28-4c55-b11a-74bdf43c142d

🎥 Demo Video

▶ Watch Demo Video

Author

Abhinav Goel

Project Type

Custom Multi-Protocol Smart Robotics Transmitter

Platform

• ESP32
• ST7920 LCD
• NRF24L01
• ESP-NOW
• WiFi
• Bluetooth

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License

This project is intended for educational, research, and robotics development purposes.