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563 posts

Ultimate Geek
+1 received by user: 89


Topic # 185645 30-Nov-2015 14:43
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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?

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483 posts

Ultimate Geek
+1 received by user: 286

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  Reply # 1437898 30-Nov-2015 15:15
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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.






563 posts

Ultimate Geek
+1 received by user: 89


  Reply # 1437944 30-Nov-2015 16:25
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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

197 posts

Master Geek
+1 received by user: 87

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  Reply # 1437955 30-Nov-2015 17:01
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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




563 posts

Ultimate Geek
+1 received by user: 89


  Reply # 1437980 30-Nov-2015 17:51
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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.

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