Wired Communication Between Two Arduinos over 20'

I currently have two Arduinos programmed for wireless communication in an airplane using Xbees but we are switching airplanes and the new one has to much interference for wireless communication. Our plan is to run some wires from Arduino 1 in the cockpit out to the Arduino 2 on the wing which is about 20 feet of wire. The cockpit needs to control 18 relays on the wing and also receive 3 analog signals. First off will TX/RX serial communication work over 20' of wire? If not what are some alternative solutions?

Note: We want to minimize the number of wires we have to run and we need very quick communication between the two.

Serial will work fine. May want to add MAX488 type buffers for RS485 so you can take advantage of the noise rejected offered with twisted pair wiring.
Shielded twisted pair would be even better.

see page 8 of the datasheet.

Sorry I am way out of my realm trying to understand this, but is it as simple as configuring two of these MAX488 into the circuit shown on page 8 of the datasheet then RO and DI pins go directly to the the RX and TX pins on each of arduinos and this will allow full duplex communication and protect against noise?

What about adding these modules?

They will boost signal from 5V TTL to +- 12V RS232. One on each side.

@OutaThisWorld - Yes.

@liudr - the twisted pair will provide better noise immunity in the aircraft environment.

Sparkfun does have some RS485 solutions, but they are half duplex only.
https://www.sparkfun.com/search/results?term=rs485

CR,

I only used RS485 in a project that had off-the-shelf control boxes connected together on one ribbon cable using RS485 protocol. I know you address each device so there can be more than 2 devices on the cable. But is there any additional advantage of RS485 over RS232? The OP only has two arduinos.

The advantage is better noise immunity.
You don't need to use any addressing - it's just buffering the TTL serial lines.

AN763 RS485 termination.pdf (234 KB)

AN723 RS485 fail safe terminations.pdf (155 KB)

I'd say get 30' of cat 3 four conductor telephone wire and start experimenting with the serial transmission. You could tape the wire along the wing with masking tspe and do some engine run ups to see if there is any electrical noise issues.

Shielded twisted pair - ground the shield at one end.

Great thanks for the advice, I have a feeling noise is going to be a big issue so I am going to try the shielded twisted wire with two max488 buffers first and I will let you all know how it goes. Thanks Again!

CrossRoads:
Shielded twisted pair - ground the shield at one end.

Is grounding at one end to prevent "ground loop"? I've done some reading on ground loops but not enough :slight_smile:

Thanks for the docs on RS485. Saved and browsed through the first one. So this communication is a bit more modern and uses differential signalling like the USB but without the NRZI?

http://en.wikipedia.org/wiki/Non-Return-to-Zero_Inverted#NRZI

Yes. Really, it's just buffering the 0/5V signal from the '328P UART.

Yes, ground the shield at one end only to prevent ground loop.