ColorPicky — The Rust Real-Life Color Picker

A real-time color picking tool powered by Rust and Embassy for the RP2350.

info

Author: Razvan Andrei Timofte
GitHub Project Link: https://github.com/UPB-PMRust-Students/project-dm-2025-razandtim

Description

ColorPicky is a compact, real-time color picking tool built in Rust using Embassy on the RP2350 (Raspberry Pi Pico 2W). It reads colors from real-world objects using a TCS34725 sensor, identifies them by name and hex code, and keeps a history of your findings. Features include:

• Real-time Color Sensing: Reads RGB and Clear channel data from a TCS34725 sensor
• Color Naming: Matches the sampled color to the nearest known color name (e.g., "Red", "Sky Blue", "Forest Green")
• Hex & RGB Display: Shows the precise Hex code and RGB values on screen
• History Mode: Stores the last 10 saved colors in a scrollable history list
• Interactive UI: Main screen with live color preview and History screen for saved colors
• Button Controls: Hold for live sampling, tap to save, double tap to switch screens, long press to clear history

Motivation

This project was inspired by practical use-cases in graphic design, photo/video color grading, and UI branding, where it is useful to capture and reuse colors from physical objects. The second goal was to gain hands-on experience with embedded Rust on RP2350 using Embassy, integrating multiple peripherals (I2C + SPI + GPIO) in a responsive application.

Architecture

The firmware is organized around three main components:

1. Sensor Module: Handles periodic I2C communication with the TCS34725 color sensor, reading RGBC values and converting them to standard RGB/HEX formats with nearest-match color naming.

2. UI/Display Module: Manages SPI communication with the SSD1283A LCD and uses embedded-graphics to render two screens:

   • Main Screen: Live color preview box, color name, and hex code
   • History Screen: Scrollable list of previously saved colors

3. Input Handler: Monitors the GPIO button and interprets gestures (tap, double tap, hold, long press) to control application behavior.

All components share an Application State containing the current sampled color and a ring-buffer history of saved colors.

Log

Week – 18-26 November

Ordered and received hardware parts (Pico 2W, TCS34725). Prepared breadboard wiring and verified power rails.

Week – 29 December - 4 January

Verified peripherals individually:

• I2C communication with the TCS34725 (basic readout and sanity checks)
• SPI communication with the LCD (initialization + test drawing)
• GPIO button input (debounce and stable reads)

Set up Rust embedded environment and Embassy toolchain, configured the target, linker settings, and flashing workflow. Resolved early build/runtime issues on RP2350.

Week – 12-18 January

Implemented the main application logic:

• Continuous sampling
• RGB/HEX conversion
• Color naming (nearest-match approach)
• UI screens + history buffer
• Input gestures (tap/double tap/long press)

Integration + stability improvements:

• Refined UI layout
• Improved responsiveness
• Added photos and documentation (pinout, usage, future work)

Hardware

The project uses a Raspberry Pi Pico 2W as the main microcontroller, communicating with a TCS34725 RGB color sensor over I2C and an SSD1283A 1.6" LCD display over SPI. A push button connected to GPIO provides user input for controlling the application.

Schematics

Bill of Materials

Device	Usage	Price
Raspberry Pi Pico 2W	The microcontroller	~31 RON
TCS34725 RGB Color Sensor	Reads RGB and Clear channel data from objects	~40 RON
SSD1283A 1.6" 130x130 SPI LCD	Display for UI and color preview	~25 RON
Push Button	User input for controlling the application	0.1 RON

Software

Library	Description	Usage
embassy-rp	Embassy HAL for RP2350	Async runtime and peripheral access for Pico 2W
embassy-executor	Embassy async executor	Task scheduling and async/await support
embedded-graphics	2D graphics library	Drawing UI elements, text, and color boxes to the display
defmt	Efficient embedded logging	High-performance debug logging via probe-rs

Links

1. Embassy - Rust Async Framework for Embedded
2. TCS34725 Datasheet
3. Embedded Graphics Documentation
4. RP2350 Datasheet
5. probe-rs - Embedded Debugging Toolkit

• Improve naming accuracy using perceptual distance (ex. CIE Lab / ΔE) and a larger palette
• Design a compact enclosure (3D printed casing)
• Add a web app