This is a LED based wall clock based on STM32 (bluepill)

It features:
 - USB interface for reprogramming and control (+ CLI)
 - BLE support (via UART) for Phone/Computer remote control
 - WS2812B LED driver via SPI hacking for fast accurate updates
 - WebBluetooth config website for convenience

How does it work?

The LEDs are connected to a single GPIO. By using SPI along with DMA we can
generate a signal that can drive the LEDs. By choosing an SPI clock of 2.25MHz
(T=444ns) we can simulate the required waveform to drive the LEDs. Three bits
are used to represent the zero and one symbol (with a period of 1333ns). By
using DMA we can guarantee that no interrupt can affect the waveform.

The BLE support comes by using the JDY-19 module, which provides a serial
bluetooth interface. The serial port is driven at 9600 bauds using interrupts
for reception and DMA for sending data. This guarantees that no data is lost.
Since the BLE protocol limits the number of bytes that a packet can contain,
the data is sent in chunks and reconstructed at the end. For that we use a
custom ASCII-based frame format, which ensure integrity while maximizing
compatibility.