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

--
Leon Heller, G1HSM
leon_heller@hotmail.com
http://www.geocities.com/leon_heller

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 :)

--

John Devereux

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

+/-3V. So, if you drive them from TTL, they tend to sleep down and that may cause different problems.

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