Oscilloscope Uart inverting the signal

Using Arduino General Electronics
1

Greetings,
I was trying to use my scope to decode an uart signal for that reason I started searching for videos. In the videos everybody invert the signal(Changing polarity from normal to invert). Why do I have to invert the signal? (Sorry if I didn't give enough information. I am still trying to learn it.)

2

It depends where in the circuit you're looking - RS232 signals are inverted to what you might expect, but the UART signals themselves may not be.

1 Like
3

Thanks for the answer,

I am trying to analyze the arduino unos rx and tx. Are they inverted.
How can I understand if a signal is inverted or non inverted?

4

Useful place to start

5

The Arduino signals are sometimes called "logic" signals or "TTL-level" signals.
The Arduino RX and TX are idle high. The start-bit is low, then the data bits, low = 0 and high = 1, then the stop bit which is high. That is non-inverted.

The RS-232 is inverted.

Some devices use inverted TTL-level UART. That is not normal, but there is no real standard.

6

Thanks for the answer,

I will definetly definitely look at it.

7

Stated another way.

The ubiquitous IC used to drive an RS232 line is the Maxim MAX232.

The MAX232 Inverts its input signal by its design. So to make it easy for processors to use the MAX232 the processor UARTs are inverted wrt the RS232 signal.

(wrt = with respect to)

8

Thanks for the answer.

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