Charlieplexing

#1

Post by danra » Sun, May 12, 2024, 12:23 AM UTC

Re: Charlieplexing

#2

Post by wepple » Sun, May 12, 2024, 2:10 AM UTC

This is nifty. I noticed a lot of the adafruit LED displays were charlieplexed but never figured to look up what that meant.

Re: Charlieplexing

#3

Post by msarnoff » Sun, May 12, 2024, 2:16 AM UTC

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)

https://github.com/74hc595/TinySimon

Re: Charlieplexing

#4

Post by MadnessASAP » Sun, May 12, 2024, 2:23 AM UTC

msarnoff wrote: post #3

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) https://github.com/74hc595/TinySimon

I love it, that's a great little build!

Re: Charlieplexing

#5

Post by voakbasda » Sun, May 12, 2024, 2:35 AM UTC

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.

Re: Charlieplexing

#6

Post by TheJoeMan » Sun, May 12, 2024, 2:44 AM UTC

msarnoff wrote: post #3

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) https://github.com/74hc595/TinySimon

Thanks for sharing! Now my wife wants one. I think adding a keychain hole would be cool!

Re: Charlieplexing

#7

Post by tomphoolery » Sun, May 12, 2024, 3:38 AM UTC

I always thought Charlieplexing was when you go on a tirade about Pepe Silvia and how Carol doesn't actually exist.

Re: Charlieplexing

#8

Post by runfaster2000 » Sun, May 12, 2024, 5:25 AM UTC

Here is a post I wrote a while back that includes charlieplexing.

https://devblogs.microsoft.com/dotnet/blinking-leds-with-ras...

Re: Charlieplexing

#9

Post by seabird » Sun, May 12, 2024, 5:50 AM UTC

msarnoff wrote: post #3

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) https://github.com/74hc595/TinySimon

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.

Re: Charlieplexing

#10

Post by tdeck » Sun, May 12, 2024, 6:00 AM UTC

seabird wrote: post #9

msarnoff wrote: post #3

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) https://github.com/74hc595/TinySimon

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.