The Cry of All ATtiny85 users: I Need One More Pin!

**rgsparber** · Feb 20, 2021, 05:17 AM

The ATtiny85 is a complete computer system-on-a-chip with enormous capabilities in a very tiny package. It is easy to run out of General Purpose Input Output pins. Here is an approach that may let you get more functionality out of these pins.

If you are interested, please, click here.

Your comments are welcome. All of us are smarter than any one of us.

Thanks,

Rick

**DIYer** · Feb 21, 2021, 04:37 AM

Thanks rgsparber! We've added your Double Duty GPIO Pins to our Electronics category,
as well as to your builder page: rgsparber's Homemade Tools. Your receipt:

Double Duty GPIO Pins by rgsparber

tags: LED, electronics

**tonyfoale** · Feb 21, 2021, 05:05 PM

Originally Posted by rgsparber

The ATtiny85 is a complete computer system-on-a-chip with enormous capabilities in a very tiny package. It is easy to run out of General Purpose Input Output pins. Here is an approach that may let you get more functionality out of these pins.
Rick

Rick,

Neat solutions. My first reaction was the same as yours - change to another chip. My second thought was to use some gates to multiplex. However, having started with computers in the early 1960s I appreciate the need/desire to use minimum hardware resources with clever programming. I abhor the modern tendency of just throwing more hardware at it.
Nice work.

**rgsparber** · Feb 21, 2021, 05:44 PM

Thanks Tony. I wondered if anyone would think it was worth anything. If this was a product, saving a penny is often worth doing. It goes directly to the bottom line as profit.

Rick

**jdurand** · Feb 21, 2021, 06:22 PM

I've gotten on the wrong side of many engineers by redesigning their stuff with way fewer parts. I was even speaker at a DesignCon re practical design.

One of the best was back in the 80s when our production floor had a bunch of house built automated machines. One particular control box on them was always breaking down, it was hard to fix because it was full of analog electronics with trim pots all over. I finally got fed up and started rebuilding them.

The engineering department got curious when production quit complaining to them about these being broken more than working. They asked the production manager who said "they haven't failed since Jerry rebuilt them". They took the cover off one box and it was almost all air with only a few parts over on one wall running in digital mode. Boy did I get in trouble for messing with the design our top engineers had come up with.