Charlieplexing
en.wikipedia.orgI 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.
The PIC10F200 has been around for a very long time. It used to be much cheaper relative to competitors but now there are many cheaper options.
I love it, that's a great little build!
Thanks for sharing! Now my wife wants one. I think adding a keychain hole would be cool!
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.
Funny to see this here — as part of a project in my “writing for engineers” class my freshman year of college, I created this page!
I always thought Charlieplexing was when you go on a tirade about Pepe Silvia and how Carol doesn't actually exist.
Here is a post I wrote a while back that includes charlieplexing.
https://devblogs.microsoft.com/dotnet/blinking-leds-with-ras...
I feel like for those of us who aren't serious electricians but do arduino like thing's we've done this, I just didn't know it had this name.
This is nifty. I noticed a lot of the adafruit LED displays were charlieplexed but never figured to look up what that meant.
Is it practical or should I just use i2c expander?