The idea for this project began in an open source hardware community I participate in, called Franzininho, in Brazil. We decided to have a Christmas project/challenge and the goal was to make a Christmas themed PCB using the WCH CH32V003 MCU (famously known as the "10 cent MCU" - 0,10 USD cost), a CR2032 battery and explore the microcontroller features. I decided to create this PC that, when assembled, is not flat, but makes a 3D Christmas tree and 16 5mm LEDs make for the balls on the tree. By doing this project, I learned a lot about this new MCU, C embedded programming in general, and using its low power modes to save energy. The board has a button that wakes up the MCU and starts a set of 4 animations for the LEDs. After a number of cycles of each animation, the board enters standby mode. The expected life of battery in standby mode is 2.5 years, so a new battery should last until the Christmas of 2025 if the ornament is turned on sparingly.

Programming steps:

The board needs software to work. It is available here: https://github.com/andremdaraujo/Projeto-Natal-2023/tree/main/Projeto-Andre-Arvore-3D/SOFTWARE/Arvore-3D. I used WCH's MounRiver Studio to develop and program the board. It'll also require a WCH-LinkE tool to connect between the board and the computer (available here: https://pt.aliexpress.com/item/1005005986225216.html?spm=a2g0o.productlist.main.9.1f3czV3ozV3oID&algo_pvid=b0752a0f-bdd1-47f1-b06d-ecf0601f3233&algo_exp_id=b0752a0f-bdd1-47f1-b06d-ecf0601f3233-4&pdp_npi=4%40dis%21BRL%2139.22%2139.22%21%21%216.22%216.22%21%40210318ec17334828358498291e86a3%2112000035188493865%21sea%21BR%210%21ABX&curPageLogUid=I3x0XYtn09lr&utparam-url=scene%3Asearch%7Cquery_from%3A).

Please notice that LEDs D1 and D2 won't light up with this version of the software. I didn't manage to make these LEDs work at the same time as the others. I had to finish the project in time for Christmas and didn't come back to fix it. But the hardware works, just needs some work on the software, which is open source! 

Additionally, for it to fully work, you'll need to assemble the board as a 3D piece, like this:

https://www.instagram.com/mechatronixlab/p/DCjyz0LRhlr/?img_index=1

https://www.instagram.com/stories/highlights/17999111168105005/