Interfacing with a 3.3V TTL serial port?

Forum 2005-2010 (read only) Hardware Interfacing
1

Do you guys think it is possible to hook a serial port operating at 3.3V TTL level directly to the Arduino, i.e. without a MAX232 chip? I've done it before with a 3.3V TX line hooked up to the Arduino's RX line, which works great... but how about the other way round? Would the Arduino's TX line at 5V destroy the 3.3V serial port?

Thanks a lot in advance!

2

You probably use three small diodes in series to drop the voltage from 5v down to 2.9v, or use two resistors of appropriate values to make a voltage divider to output at ~3.3v.

3

I would use a potential divider with a catcher diode up to 3V3 just to be sure.

4

I also have some questions about TTL signals (http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1270408455)

In a nutshell:

My C328 serial camera also had 3.3 TxD and RxD, I use a Arduino Mega to interface with it. The C328 sends 3.3V signals from its TxD pin to the RxD pin of the Mega that requires 5V (I assume) Do I need to step up this voltage? If yes, how can I do this?

@ Grumpy_Mike:

I use a voltage divider using two resistors to go from 5V to 3.3V why and where to use a diode? I did some research on the Internet and all voltage dividers do not use a diode. This does not mean diodes are not a necessity, but why?

Thanks in advance.

/me