I saw that on CNX but why is it interesting? The board isn't unusually small compared with something like a Xiao or QtPy, It is 2.2cm * 3 cm, almost 2x the size of a Xiao, which is cheaper and much more powerful.
This is notable not because of the board itself, but because of the incredibly small footprint of the MCU on it. This chip is ~40% smaller than the already tiny Kinetis KL02.
Although I must wonder if there are many applications where .5mm difference in package size is really meaningful
Embedding a keylogger not merely in a cable, but actually in a connector?
The idea is that you only use the board for development, and use the 1.6mm x 1.45mm (note: mm not cm) chip on a tiny custom board in production.
What are examples of tiny boards where MCU size would matter? Usually boards are dominated by other components anyway.
Although those are probably always some more specialized ASICs instead of some general purpose MCUs
I guess that angle is interesting, but for most of us here, the board doesn't help that much in that case. The chip docs are all in Chinese, and it is a 4x4 CSP package with specific pin assignments so you have to route some very tiny PCB traces. I wonder what PCB fabs can handle that without charging a fortune. I believe there are some almost-as-small parts where you have more routing flexibility and a reasonable GCC port.
What would you do with a tiny, tiny MCU?
Embed it in tiny, tiny things.
Make it a bootloader for a merely tiny MCU?
Add a humane user interface to action camera with crappy ui
A board called T-HC32 would be better priced at $4.20