Serial Port Voltage

[GatorGuy]

When I tested my serial port's voltage I am getting reversed polarity. :? Is this normal? It is negative voltage? As you can tell I am really new to working with the serial port.

 

[Nigel Goodwin]

When I tested my serial port's voltage I am getting reversed polarity. :? Is this normal? It is negative voltage? As you can tell I am really new to working with the serial port.

Check my RS232 PIC tutorial, which explains it!.

 

[Jay.slovak]

When I tested my serial port's voltage I am getting reversed polarity. :? Is this normal? It is negative voltage? As you can tell I am really new to working with the serial port.

LOG. 1 ~ -8V and LOG. 0 ~ +8V....

Always Check Nigel's tuttorials!

 

[checkmate]

It's normal.
https://www.lammertbies.nl/comm/info/RS-232_specs.html#phys
The readings I get from standard serial ports are typically +-10-16V. Laptops give weaker voltages, maybe +-8V.
Because most uCs take in 5V (or <3V for low voltage uCs), you will need a level shifter IC to protect the uC. That's the function of the MAX232 chip.

 

[Jay.slovak]

It's normal.
https://www.lammertbies.nl/comm/info/RS-232_specs.html#phys
The readings I get from standard serial ports are typically +-10-16V. Laptops give weaker voltages, maybe +-8V.
Because most uCs take in 5V (or <3V for low voltage uCs), you will need a level shifter IC to protect the uC. That's the function of the MAX232 chip.

MAX232 is performing level shifting AND inverting....

 

[checkmate]

MAX233 is performing level shifting AND inverting....

Hey, no offence. But inversion is also a type of level-shifting, aint it? :lol:

 

[Jay.slovak]

MAX232 is performing level shifting AND inverting....

Hey, no offence. But inversion is also a type of level-shifting, aint it? :lol:

That's true, I just wanted to point this out