RS422 Pinout

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kenkeniff

628 posts

Ultimate Geek

#185645 30-Nov-2015 14:43

I'm trying to connect an RS422 SSI device to a RS422 USB adapter.

Outputs on RS422 device are labelled as:
SCK
CLK
RXD
TXD
GND

Inputs on RS422 adapter are labelled as:
T+
T-
R+/D+
R-/D-
GND

What would be the correct way to connect this up?

roobarb

653 posts

Ultimate Geek

Trusted

#1437898 30-Nov-2015 15:15

Looks like your RS422 USB is differential, hence T+/T- and R+/R-

But your SSI device uses clocks. The SCK might refer to send-clock and CLK as a received clock.

Unless your RS422 adapter is expecting and providing clocks it will play merry havoc with your differential data.

kenkeniff

628 posts

Ultimate Geek

#1437944 30-Nov-2015 16:25

Yeah, not sure if it will work but I'm trying to connect two synchronous serial devices via a PC as below:

SSI RS422 Device 1 > RS422 USB Adapter > PC / COM PORT REDIRECT > RS422 USB Adapter > SSI RS422 Device 2

PolicyGuy

1727 posts

Uber Geek

ID Verified

Lifetime subscriber

#1437955 30-Nov-2015 17:01

Why would you do it that way?
If you're just joining two RS422 devices, just use a twisted-pair data cable (not a UTP LAN cable) "Differential signaling can transmit data at rates as high as 10Mb/Sec, or may be sent on cables as long as 1500 meters" [https://en.wikipedia.org/wiki/RS-422]

If you've only got UTP LAN cabling, it should work, but not at the full data rate or the full distance

kenkeniff

628 posts

Ultimate Geek

#1437980 30-Nov-2015 17:51

PolicyGuy: Why would you do it that way?
If you're just joining two RS422 devices, just use a twisted-pair data cable (not a UTP LAN cable) "Differential signaling can transmit data at rates as high as 10Mb/Sec, or may be sent on cables as long as 1500 meters" [https://en.wikipedia.org/wiki/RS-422]

If you've only got UTP LAN cabling, it should work, but not at the full data rate or the full distance

Once I confirm it working through one PC, I will be looking to extend it over LAN / VPN.