Rising edge writing on digital outputs- ANOMALY

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Hey guys! :slight_smile:
At first I would like to greet everyone on the forum, as this is my first post.
I found some anomaly during the work on my project, impossible for me to understand.

I was making my furnace controller project. I was playing with connecting of RTC to I2C bus, but then I got idea to check work of square wave generator output attached to the clock.

I prepared the software, using library bounce.h and function of it- fallingEdge().

Before even I connected the SQW to the digital output, amazing thing happened.
I don't even had to plug the the wire, clock was working and measuring the rising edges!

What was even more suprising, rising edges are couting when I touch the output, with any wire. Even unplugged. Or even when I put that wire close to output. Or even, when instead of wire I put my hand close to output. Without touching it.
When I take my hand away, it just stops.

There is around (hardly measuring) 12 rising edges per second. Anyway, 10 rising edges are visible faster then second.

Can somebody light for me that issue? Thank you very much for any help. I'm very fresh at Arduino. This destroyed my mind.

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What was even more suprising, rising edges are couting when I touch the output, with any wire.

Which output? One of the pins on the Arduino? Configured as output?

Or one of the pins of the Arduino that is configured as input.

In which case I guess you're talking about an effect caused by a floating input.

A floating input is an input that is not connected to anything. Inputs are high impedance and pickup noise and when your read those, you just read random values.

Nothing to worry about if you have something connected to it like the output of the clock module (mechanical contacts don't count).

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OOPS, might have forgotten that that output might be open drain; in which case a pull-up is required.

Check the datasheet of the rtc chip.