can an AVR generate a RS-232 signal with a VCC of 5V?

computer.

one

There's 3rd party clones of the MAX232 that do equally well. I frequently use the ST232, which is available from most distributors.

Rob

one

If you use a software UART you can get the correct polarity signals. They only swing from 0V to +5V, but that is acceptable to most PCs. I tried this once, and it worked OK.

Leon

Also if you're really cheap you can use a not gate on the hardware uart. Don't forget to put a resistor + 5V zener on the RX side.

It works ok in some situations.

computer.

this

"Brett" writes:

Cheap?? For extra cheapness, leave out the zener. The RX gate input protection diodes will swing into action and take it's place.

In fact, that series resistor looks a bit extravagent too.... RS232 is current limited already, after all :)

And I've tried it a dozen times: it works Wade Hassler

Most of RS232 drivers can accept TTL levels, but not all of them.

I used to think that it always works, until I encountered the PC from Dell (can't remember the particular model). That was the first occasion.

I was burned the second time with the RS232 drivers from SIPEX. Those drivers are switching to sleep mode if the input voltage is inside

Vladimir Vassilevsky, Ph.D.

DSP and Mixed Signal Design Consultant

Me, too. It's under 1 Euro (Dollar) in single quantities and only needs 100nF capacitors (like the MAX232A ;-)

Jan-Hinnerk