RC Transmitter

Open-source design and code for a 3D-printed pistol-grip RC transmitter.

Overview

A general-purpose RC transmitter designed to control multiple vehicles by swapping configuration profiles. Currently used with an RC snowblower and an engineering test rover.

Features

• Wireless control via nRF24L01+ with bidirectional telemetry (acknowledge payloads)
• Touchscreen UI on a 240x320 TFT with resistive touch input
• Live telemetry display: battery voltage, board temperatures, motor currents
• Motor stop (M-Stop) soft button on the touchscreen
• Joystick input for throttle and steering

Planned

• Joystick calibration via touchscreen UI
• Physical button matrix (multiplexed)
• SD card configuration profiles for multi-vehicle support
• Settings/setup menu

Hardware

Transmitter

• MCU with dual SPI buses (currently Teensy 4.1)
• Adafruit 2.8" TFT Touch Breakout — ILI9341 display with resistive touchscreen (SPI1)
• nRF24L01+ radio module (SPI0)
• Analog joystick (steering + throttle)

Receiver (Rover Test Platform)

• Arduino Mega
• nRF24L01+ radio module
• Basicmicro RoboClaw motor controller

Project Structure

RC Transmitter/
├── main/                 # Transmitter firmware (Arduino IDE)
│   ├── main.ino          # Setup, loop, radio, global state
│   ├── config.h          # Pin assignments, constants, shared types
│   ├── touchInput.ino    # Touch state machine
│   ├── screenManager.ino # Screen transitions and button management
│   └── drawScreens.ino   # Screen drawing and UI updates
├── test_sketches/        # Standalone test/reference sketches
├── stl/                  # 3D printed enclosure files
├── docs/                 # Documentation and images
├── LICENSE               # GPLv3
└── README.md

Pin Assignments (Teensy 4.1)

Active pin mapping for the current build. Also maintained in Google Sheets.

Display & Touch (SPI1)

Function	Pin	Notes
CLK	D27	SPI1 clock
MISO	D1	SPI1 data in
MOSI	D26	SPI1 data out
TFT CS	D0	Display chip select
TFT DC	D2	Display data/command
Backlight	D3	PWM brightness control
Touch Y+	D24	Analog (A10)
Touch X-	D25	Analog (A11)
Touch X+	D28	Digital
Touch Y-	D29	Digital

Radio (SPI0)

Function	Pin	Notes
SCK	D13	SPI0 clock (default)
MISO	D12	SPI0 data in (default)
MOSI	D11	SPI0 data out (default)
CE	D9
CSN	D10

Inputs

Function	Pin	Notes
Steering	D14	Analog (A0) — wheel input
Throttle	D15	Analog (A1) — trigger input
Joystick X	D17	Analog (A3) — e.g. chute aim L/R
Joystick Y	D16	Analog (A2) — e.g. chute aim U/D

Button Matrix (planned)

Function	Pin	Notes
Row A	D30	Digital
Row B	D31	Digital
Row C	D32	Digital
Row D	D33	Digital
Col 1	D34	Digital
Col 2	D35	Digital

CAD Source

3D design for the transmitter enclosure is on OnShape.

Dependencies

Install via Arduino IDE Library Manager:

• RF24 (TMRh20 fork)
• Adafruit GFX Library
• Adafruit ILI9341
• Adafruit BusIO

Bundled with the Teensy board package:

• TouchScreen — included in {teensy_package}/libraries/TouchScreen, API-compatible with Adafruit TouchScreen

Receiver also requires:

• RoboClaw Arduino Library

Development

This project is developed with assistance from Claude (Anthropic), used for code architecture, refactoring, and documentation.

License

This project is licensed under the GNU General Public License v3.0 — see LICENSE for details.