Arduino Uno pinouts only 0.5 volts?

[hurricanehenry]

OK I made some adjustments to the code.

What is different now is that I made sure Pin 13 is LOW.

Before, the Pin 13 LED was turned on (default?)

NOW with the Pin 13 LED turned off, Vbase reads from -10mV to +50mV which is much less than +200mV before, and Vtop reads almost 5.0v exactly (5.02, 5.05).

So it might have been coupling (inductive coupling?) from Pin 13 right next to Pin 12, giving the non-Zero voltage?

Here's the code just FYI. Very simple test code.

void setup() {
  pinMode(12, OUTPUT);
  pinMode(13, OUTPUT);
  digitalWrite(13, LOW);
}
 
void loop() {
  digitalWrite(12, HIGH);
  digitalWrite(12, LOW);
}

FYI the frequency of this square wave (which is not super super stable) is around 94 kHz.

[rs20]

So it might have been coupling (inductive coupling?) from Pin 13 right next to Pin 12, giving the non-Zero voltage?

For the record, DC cannot be inductively coupled (unless there's literally an inductor connecting them, often what inductors are used for is to set a DC bias this way), nor can it be capacitatively coupled.

[hurricanehenry]

OK so it's weird. I added a 1/1000th second delay. (f = 500 Hz now)

void loop() {
  digitalWrite(12, HIGH);
  delay(1);
  digitalWrite(12, LOW);
  delay(1);
}

And now the 200mV LOW voltage is back, same with the Vtop, now back to 5.2v.

[hurricanehenry]

So it might have been coupling (inductive coupling?) from Pin 13 right next to Pin 12, giving the non-Zero voltage?

For the record, DC cannot be inductively coupled (unless there's literally an inductor connecting them, often what inductors are used for is to set a DC bias this way), nor can it be capacitatively coupled.

yes but this has become AC hasn't it? The voltage rises and falls still happen, and electromagnetic effects still occur due to this changing voltage over time, no?

Anyway the added delay seems to point to another factor.

[rs20]

For the record, DC cannot be inductively coupled (unless there's literally an inductor connecting them, often what inductors are used for is to set a DC bias this way), nor can it be capacitatively coupled.

yes but this has become AC hasn't it? The voltage rises and falls still happen, and electromagnetic effects still occur due to this changing voltage over time, no?

You're claiming that the DC voltage from pin 13 is being coupled into pin 12 -- which is what I'm saying doesn't make sense, irrespective of whether pin 12 has AC on it.

[hurricanehenry]

For the record, DC cannot be inductively coupled (unless there's literally an inductor connecting them, often what inductors are used for is to set a DC bias this way), nor can it be capacitatively coupled.

yes but this has become AC hasn't it? The voltage rises and falls still happen, and electromagnetic effects still occur due to this changing voltage over time, no?

You're claiming that the DC voltage from pin 13 is being coupled into pin 12 -- which is what I'm saying doesn't make sense, irrespective of whether pin 12 has AC on it.

Ah yes, you're right. My bad.