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Topic: Wireless RS422 (Read 169 times) previous topic - next topic

Mpboyer3

The company that I work for connects 2 junction boxes via RS422 using a cable.  I am wanting to send this data wireless, I originally thought that I could do it with a pair of XBee radios using a grove board but Digi says that I need to use something else as the radios can't pass the data. One option was a RS422 to RS232 converter which seem to be pretty expensive. The other he suggested was using an Arduino. I don't know much about them or what components that I would need to accomplish this task. If anyone can help I would greatly appreciate it. I am fairly electronic/computer literate but don't really know much about Arduinos or the components that I would need.

Thanks in advance.

jremington

#1
Jun 13, 2018, 04:29 pm Last Edit: Jun 13, 2018, 04:52 pm by jremington
Quote
as the radios can't pass the data
That is not correct, so discount advice from that source.

You will need an RS422 adapter to convert the signals to 0-5V levels. Then Arduino and any radio, or several other types of radios, possibly including XBee, can send the data onward.

The actual details depend on the data rate and the protocol (whether handshaking signals are used, etc.) of the present connection, so the more information you can post about that, the better the help you will receive.

pylon

As RS422 is usually full-duplex this might limit the selection of radio modules. But as jremington already stated, depending on the used protocol this might be irrelevant.

DrDiettrich

Wireless together with RS-422 is nonsense. RS-422 is based on current, which requires a pair of wires.

Behind the RS-422 cable resides a UART, which encodes bytes into a stream of serial bits. Connect these UARTs to dumb RF modules, instead of the RS-422 driver/receivers, and the communication should work immediately.

avr_fred

Quote
Wireless together with RS-422 is nonsense. RS-422 is based on current, which requires a pair of wires.
Oh my, even more nonsense.

RS422 and it's half duplex brother (or sister) RS485 are based on differential voltage. They can handle multi-megabaud speeds while utilizing hundreds or even thousands of meters of proper cabling. Current loop based systems are inherently speed limited, 300 baud maximum was typical for current based signaling systems.

The other commenters are quite correct that the details matter.

jremington

#5
Jun 14, 2018, 01:09 am Last Edit: Jun 14, 2018, 01:11 am by jremington
@Mpboyer3: if you want to replace the existing RS422 connection with a wireless connection (not what I was thinking about), then it is essential to know what is on each end.

Some types of RS422 connections are intended for smart devices, with extra control signals, and are not simply a much faster, long distance replacement for RS232 or other types of serial data transfer.

Let us know.

DrDiettrich

RS422 and it's half duplex brother (or sister) RS485 are based on differential voltage.
Please learn to distinguish voltage from current before spreading more nonsense.

RS-422 is also known as the "current loop" serial interface.

jremington

DrDiettrich: please inform yourself. RS-422 is most definitely NOT a current loop interface.

Quote
Officially, the RS-422 standard's title is Electrical Characteristics of Balanced Voltage Digital Interface
Circuits, and is published by the ANSI Telecommunication Industry Association/Electronic Industries
Association (TIA/EIA).

DrDiettrich

Sorry for the confusion, you are right :-(

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