Ornament

Arduino-powered Christmas Ornament (or badge, or anything else)

A custom LED Christmas ornament with advent calendar functionality, built using Arduino and KiCad. This project can easily be adapted to other formats such as a badge by changing the PCB layout.

Key features:

• 30 individually-addressable LEDs
• PWM LED control, with support for up to 12 (or more) simultaneous LEDs
• Fade-in / Fade-out support
• Advent calendar mode included
• User-configurable advent date and brightness settings
• Light level measurement (optional)
• Current measurement via a precision 1-ohm current sense resistor and precision amplified ADC circuit (intended to help optimize power usage prior to software finalization) (optional)
• Optimized to fit within the 4k / 256 byte memory limitations of the ATTiny414, but is also compatible with larger variants such as the ATTiny 814/1614/824/1624/3224
• Production software is configured to run at 8MHz to optimize power usage (instead of default 20MHz) - this can be changed if higher PWM frequency is desired, for example. (test software still runs at 20MHz)
• >30 days run time on one set of 3x AAA batteries, using default Production software (5 hours/day on, with auto timer). Can be run on other 3-5VDC power sources like CR2032 for shorter durations (however, >3.5V is required for 2.8V LEDs or higher - so stick with ~2.2V LEDs or lower if using 3-3.3V power sources).

Project Structure

This project is organized into three main directories:

1. KiCad Files (KiCad_PCB_Ornament/)

Contains all KiCad design files for the PCB:

• Schematic files (.kicad_sch)
• PCB layout files (.kicad_pcb)
• Component libraries (.lib, .dcm)
• Footprint files (.kicad_mod)
• Exported fabrication files (.gbr, .drl) (for the example design / messaging)

The PCB layout can be easily customized with your own text, or into a different physical format or size (like a badge) using KiCad - however if modifying the layout you'll have to re-route the board as well of course. I chose to put the control electronics on the front of the board (to be geeky), but they could easily be moved to the back to clean up the appearance.

NOTE: the board design includes optional current monitoring circuit and light sensing circuit. Neither of these are implemented in the production software, however they are fully functional and usable in the test software. Those features can be ported to production as needed, or removed or unpopulated on the PCB.

2. Production Software (Ornament_production_1/)

The main firmware for the ornament controller:

• Main Arduino sketch (Ornament_production_1.ino)
• Configuration and constants
• LED control algorithms
• Date setting and brightness adjustment routines
• Software fits in under 4k of flash, and uses approx. 70 (of 256) bytes of dynamic storage

3. Test/Validation Software (Ornament_test_1/)

Code for testing and validating the PCB functionality:

• Calibration routines
• Basic functionality tests
• Hardware verification code
• Software uses less than the ATTiny414's 4k of flash and 256 bytes of dynamic storage
• Includes ADC routines for current monitoring and light level measurement, if needed (not used in production code)

Production Features

• Advent calendar display (December 1-25)
• Custom LED patterns with twinkling effects, including PWM fade-in, fade-out
• Date setting via button interface
• Adjustable brightness levels (10% to 100%)
• Sleep/wake cycle automation
• Preview mode for manual activation during sleep, without affecting 24-hour auto-on timer

Hardware Requirements

• Microchip ATtiny414 microcontroller (or others in that series)
• Custom PCB with LED matrix
• Power switch and button for user interface
• Battery or power supply for operation
• Optional serial monitor to view diagnostic output on the UART connections (test software only by default)

Getting Started

1. Clone this repository
2. Open the KiCad project to view or modify the PCB design
3. Use the Arduino IDE to compile and upload the production firmware to the completed PCB
4. Test with the validation software to verify hardware functionality
5. Modify and install the production software as desired

License

This project is licensed under the MIT License - see the LICENSE file for details.

Notes

• Custom LCG (Linear Congruential Generator) for random number generation to save flash space
• Charlieplexing technique for LED control - it uses 6 GPIOs to allow individual addressability for up to 30 LEDs.
• PWM LED control for up to 12 LEDs simultaneously, using 3x 32-step groups for each PWM cycle (4 LEDs per cycle)
• (more LEDs can be controlled simultaneously via configuration, but will limit maximum LED brightness)