I recently had to program quite a few microcontrollers and got annoyed at one hand having to both hold the PCB and use the keyboard to program a chip. Therefore, I decided to upgrade my programming pen, so that I could trigger programming with its build-in pushbutton. The solution I came up with was to add a tiny USB keyboard circuit to the pen’s interface.
One minor annoyance when programming microcontrollers in-circuit, is that often quite a bit of PCB space is lost due to the programming connector. Furthermore, when you have to program many chips, repeatedly reconnecting the programming cable quickly becomes a chore. So when I found an article about constructing a programming pen that would help solve both of these problems, I decided to build one for myself.