The Magic Key is a little weekend project primarily started because I had a bunch of ST7789 1.3 inch displays lying around in a drawer.
This page will document the design of the device as well as development for it.
Hardware Design and Development
As mentioned earlier, the idea was a result of some left over ST7789 displays. Essentially any STM32 MCU with a USB port could have been used, but a number of reasons lead to the use of the STM32L432 MCU:
1. The STM32L432 is one of the few STM32 MCUs which do not require a crystal to work with USB
2. Built-in hardware random generator
3. Plenty of built-in flash - in fact the STM32L432KB have double what is specified.
For extra storage a W25Q128 flash was added, mostly because this is a basic part readily available at JLCPCB.
Before ordering, KiCAD 3D renderings: