RS232 and RS422 Communications


I’m working on a project that requires several Arduinos communicating with each other via RS422 and each one with other peripherals via RS232.

So far I’ve been using Arduinos MEGA 2560 with MAX489 (for rs422 communication) and MAX232 (for rs232 communication) and it has been working great. But now I need to use an arduino DUE along side with the others MEGA, i.e., communicating via RS422 with arduinos and via RS232 with some periphericals.

The problem I’m facing is with the voltage levels in the TTL communication. In MEGA I have 0 to 5V TTL, while in DUE I have 0 to 3.3V TTL. As far as I have seen in the both ICs datasheets, if I connect DUE to them, I’ll end up frying it.

So, my quetion is: Is there any alternative to these ICs that will work with DUE? Or if there is a configuration on the electronics side that will allow me to use these ICs with DUE?


Years ago, the standard was 5V TTL circuits. At that time RS-232 required a separate power circuit for the chip, having both positive and negative rails. Today's chips have an internal converter, and many of them can work with either 5 V or 3.3 V power input, and provide the necessary voltages. Check your datasheet for the chip that you are using. It is likely that it will run using 3.3 V power, Without a problem.

if not, Look at eBay or your favorite supplier. you should be able to get an appropriate serial converter for your application.

You can run a MAX232 on 3.3v and it will probably work. There are specific MAX chips for 3.3V. I use the MAX202EEWE a lot.

For EIA-485 use the MAX3485 chip.


for RS232 I've used a lot of Sparkfuns MAX3232 boards with the Due. Runs fine at both 3v3 and 5v. I now use that chip directly in my custom boards.