reuse serial?

Is there any reason I cant re use RX and TX as momentary switch inputs since I'm out of pins? I don't specifically ever use serial transfer in my sketch.

Also, If I did use serial, and TX was pulled to ground accidentally, would that cause any damage? I assume the hardware ports are protected.

Of course, if I pull down RX, the sketch wont load via USB.


I assume the hardware ports are protected.


There are issues with the pull-up resistors used on those pins. In principle you can use them if you want to. In my VGA output test documented here:

Towards the bottom of the page I used pins D0, D1 and D2 for RGB signals to the monitor. So yes, it can be done. But for inputs - caveat - check the schematic for the pull-ups. I think you can probably work around them. For example, if they have pull-ups, ride with it, and make your switches ground the pins. Make sure if you do this that you don’t happen to turn Serial on (eg. Serial.begin) because then you may damage the pins.

What if I was receiving data to the Arduino and I had RX pulled low at that time by a switch. It would present a short to the output of the programmer. Not good.

I think that maybe to use RX as an input, I should use a 1k res->switch-GND from RX pin. Set the chip to pull up pin 0. To use TX as an input, same thing, in case TX was enabled accidentally and my switch was pulling TX low. Set the chip to pull up pin 1.

Nick, Your video project looks really nice. Do you have an easy suggestion if I just want larger letters or numbers on the screen?

Or maybe just a single large number?

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