An Open Source & Open Hardware project.

Demo gif (loads a bit long) 👇

The core of this project is MSP430G2553 mictrocontroller by Texas Instruments and two SN74HC595N 8-bit shift registers. Each 8-bit shift register controls 8 3mm red LEDs. Also resistors, capacitors, slide switch, tacticle button, DIP sockets, Li-ion akku 3.7V, a JST connector.

Check schematics below to get values for resistors and capacitors.

Here are all used components 👇

And this is how assembly looks like 👇

I used KiCad to design hardware. Source files are located in pcb folder.
This is a schematic diagram 👇

KiCad project fies for PCB as well as Gerber files for PCB production are also located in pcb fodler.
This is a PCB design 👇

With highlighted nets 👇

Firmware for this project was written in pure C, operating with IC registers directly (without platformio or any other ports of arduino libraries). It requires some deeper knowledge of MSP430G2553 datasheet and hardware communication protocols, but drastically reduces binary size. It's only 14 KB!

There are 6 different patterns of LEDs blinking. They are store in 2 dimensional arrays of bytes.
Timer intrruptions are configured to be called every 0.1 second. IC goes over array and sends data to 8-bit shift register. Communication between the microcontroller and 8-bit shift registers is done via SPI protocol. When IC is not busy, it goes to low power mode.

https://www.youtube.com/watch?v=liG8lNvPkbY

https://www.instructables.com/Electronic-Heart-Valentines-Day-Gift/