How to convert RS-485 to RS-422

[ErichP]

Hi guys,

I have application where we need to send hd-sdi over single mode fiber with RS data about 6km, unit which we are using in this application is 1ch HD-SDI over fiber with reverse rs-485 data. Is there any successful way to convert RS485 to RS 422?
I found this converter in google search: RS485/RS422 Converter/Repeater
I am looking for recommendations, or stay away from's.
I also would be interested in a USB option if available for true portability (something I can throw in my laptop case).
Any help would be appreciated!
Thanks,
E

 

[AnalogKid]

485 and 422 are essentially identical hardware protocols with one major exception. 422 allows for only one transmitter on a bus, and it is permanently enabled. 485 allows multiple transmitters; only one at a time can be enabled, and the others are in tri-state (high-impedance) mode, If you are dealing with a dedicated comm link with one transmitter at one end and one receiver at the other, chips for either protocol should perform identically.

The link you posted is for a 232-to-485/422 converter. That is a very different thing, because the 232 signal voltage levels are quite different. Note that the other end works for both 485 and 422 with no changes of adjustments.

If 232-485 is what you really are after, I can walk you through it. It basically is 2 chips (although today there probably is a single chip that does both functions), a 232-to-TTL interface and a TTL-to-422/485 interface. Both parts run on +5 V only. The 232 chip uses on-board charge pumps to generate +/-9 V for the 232 signal lines.

ak

 

[ErichP]

thanks for your answer, do you know where I can buy this product 484 to 422 converter?

 

[AnalogKid]

As far as I know, there is no such thing. In a single-channel application like yours, RS-422 and RS-485 are identical.

ak

ak