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 FC-SCG FACET-Card - RS485 
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Joined: Thu Aug 29, 2019 4:53 pm
Posts: 9
Post FC-SCG FACET-Card - RS485
I see that there is a FACET Card that lists RS485 capabilities. I do Building Automation, and I am looking to see if it will allow for BacNet over RS485.

https://fit-iot.com/web/product/facet-c ... arts-fscg/

I understand I would need to supply the software side of things, I just need to know if I can land 2 wires to the card and have it do the switching and such. There was no real picture that showed anything but what appeared to be CAT5 plugs on the page.

BacNet would be classed under UART, and the flavor I am looking to implement would be 2 or 3 wire BACNet. I also have use for BACNet over ARCNet using a 2 wire connection, or even Coaxial connection. I would be happy to provide more details.


Wed Sep 04, 2019 1:30 am
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Joined: Mon Dec 25, 2017 4:21 pm
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Post Re: FC-SCG FACET-Card - RS485
You should find the FC-SCG schematics and production files at:
http://fit-pc.com/wiki/index.php?title= ... rds#FC-SCG


Wed Sep 04, 2019 10:43 am
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Joined: Thu Aug 29, 2019 4:53 pm
Posts: 9
Post Re: FC-SCG FACET-Card - RS485
I looked at that link and found very little of use. The card is pictured beautifully, but it is only when you get the documentation open that you find the pretty picture is missing the main piece - the part that seems to actually talk UART - and the diagram you do get is really hard to see - it looks like 2 coax connections - but RS485 is an electrical standard that does not really limited to coax at all - so is there more that I am missing? also when you add this piece where do the coax ports go? do they replace some of the ports on the front of the device around the power button and the USB ports? if there is a coax port- piece, is there a different piece that is not pictured that shows the RS232 connections? the RS485 connections? where do the ports penetrate the exterior? Why is this not shown in the documentation?

Maybe this gives a better idea as to what I am looking for, what is perhaps missing from the documentation, and what you might want to include to help out.

Again I REALLY appreciate the time you are taking to respond. :D


Fri Sep 06, 2019 2:50 am
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Joined: Mon Dec 25, 2017 4:21 pm
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Post Re: FC-SCG FACET-Card - RS485
As described in the fit-pc WiKi page, the FC-SCG has CAN, RS485/RS232 COM Port and GPIOS.
The CAN and COM ports are interfaced via an RJ45 port (pinout described in the schematics at the fit-pc WiKi page provided in my last post).

The fitlet2 is designed in a way that all supported FACET cards penetrate through the right side panel, when looking at the fitlet2's front panel where the power button is.

At the FC-SCG product page, you could open the 360 degree 3D view to have a better understanding of the product's construction when FC-SCG installed.
FC-SCG product page: https://fit-iot.com/web/product/facet-canbus-rs232-rs485-gpios-fitlet2-parts-fscg/


Sun Sep 08, 2019 1:13 pm
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Joined: Thu Aug 29, 2019 4:53 pm
Posts: 9
Post Re: FC-SCG FACET-Card - RS485
Wowee, of all the interfaces I have had to mix, I have not had to mix RJ45 and RS485. I would need to find an adapter that makes the RJ45 pinout turn into what I need. Not to be a big downer, but that might be one of the oddest combinations I have ever seen. You may have better sales with a different interface for RS485 - I know I have no idea what all you do, but it is a suggestion.

An adapter I have and that I love is this:
http://www.usconverters.com/usb-rs485-adapter-cable

It is not at all the right thing for this application, but it has a very nice close up of the RS485 connection I need. Most of the RJ45 to RS485 connectors I find convert to a DB9 plug. Do you happen to have options to get to the 2 or 3 wire plug shown on that adapter cable I posted?

The terminal designations are G for ground, A for negative and B for positive. I do not know your level of familiarity, so I figured it would be good to be thorough.


Sun Sep 08, 2019 3:48 pm
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Joined: Mon Dec 25, 2017 4:21 pm
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Post Re: FC-SCG FACET-Card - RS485
There is no industry standard for interfacing with RS485.
We do not have an adapter to offer as mentioned in your last post.
Crimping an RJ45 cable wired for RS485 on both ends should be fairly easy.


Mon Sep 09, 2019 10:27 am
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Joined: Thu Aug 29, 2019 4:53 pm
Posts: 9
Post Re: FC-SCG FACET-Card - RS485
Thanks a lot for the prompt responses!

Yes, RS485 is a little hard, since there is no industry standard. I realize that my personal experience should not be taken as the only viewpoint, but maybe you can add my viewpoint to yours and make something cool out of it.

Most all of my RS485 exposure is for BacNet and Modbus. I do run accross other flavors, but the physical interface is the same. The terminal designations shown are consistent with the adapter I linked to. The wire is usually 22/2 awg or 22/3 with low capacitance. Reaching baud rates of 38.4kbaud to 76.8kbaud. I can link to something with some tech specs and installation details if you like.

Without an appropriate interface, I am looking at several options. The most reliable is a Bacnet MSTP to Bacnet IP Router. But these are between $150-350 each and I may use as many as 4 to 6 of these. These numbers are intended to provide a reference point for market feasibility if you may want to consider a new FACET card. If the price point is below $75 - 100 per connection, you have a money maker. 2 connections on a card with a price point similar to the other FACET cards would be a good thing. I would say 4 connections would be ideal, as it covers many many applications. I usually use between 2 and 4 connections. Sometimes 6.

You guys are great. Keep up the good work!


Mon Sep 09, 2019 3:30 pm
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Joined: Mon Dec 25, 2017 4:21 pm
Posts: 342
Post Re: FC-SCG FACET-Card - RS485
Thank you for your suggestions and kind compliment.

Compulab encourage customers to design their own FACET cards based on our design or even their own.
This is why we provide full industrial documentation, and may provide further information if required.


Tue Sep 10, 2019 8:13 am
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