Planck keyboard powered by STM32F103C8T6
Purchased several of these boards on
eBay. They are as cheap as the Pro Micro clones and have just as bad build quality. There are two styles of the boards, with two different USB connectors. The one that looks more secure with 4 mounting points and the one pictured below with just two solder tabs. What you gets is random. I purchased from two different sellers and got the opposite version of what they each pictured in their auctions. I have tried 3 of the 7 I purchased. 1 was DOA with a solder bridge on the USB data lines.
Matrix scanning speed is about as fast as the
ARM based Teensy's. 10000 scan cycles per second. This is with the default 30us delay. It can probably go even faster.
These require a 3.3v TTL serial adapter to program them. You can also get these for a few dollars on
eBay.
I soldered the serial port pins and the boot jumper/reset pins to a piece of SIP header so they can be accessed when the keyboard is assembled.
The major downside of these boards are the size and the height of the components. The jumper headers are the tallest parts but can be removed. There are also components on the bottom of the board so it does not lay flat.
