I used Charlieplexing to drive four LEDs, four buttons, and a beeper from a 6-pin PIC10F200 with only four GPIOs. (and one is input-only!) It was a lot of fun working out the correct TRIS/GPIO combinations. (and fitting the whole thing into 256 instructions and 16 bytes of RAM was fun too)
Have you seen any industry applications of that part? I'm seeing 51 cents/piece at 3k on DigiKey, which is pretty wild when more fully featured OTP parts are available for less than ten cents.
In the early 00’s, I used this technique to write a keyboard driver for a handheld computer, using a PIC microcontroller. The method was shown to me by a senior EE who previously worked on HP calculators, after HP had outsourced that division to another country. I learned a lot of tricks like that while at that job, as I was the only one on the team who was not a former senior HP engineer. They knew their stuff, and their stories about the outsourcing made me forever reluctant to buy anything made by HP.
https://github.com/74hc595/TinySimon
reply