How to use: RS-485 vs RS-232 Camera Control Cabling
In this tech support Tuesday Andy Chatfield reviews the RS-232 and RS-485 PTZ camera control options. A common technical support question for Andy is “Should we use RS-232 or RS-485 for camera control?” Andy answers this question and reviews the differences between RS-232, RS-485 and RS-422 (which PTZOptics cameras do not support).
Andy goes over the complete Serial Joystick connection diagram for controlling multiple cameras and makes suggestions on cabling that can be used. A common implementation of camera control cabling is actually using something that integration companies already have run in the walls such as Cat-5 or Cat-6 cabling. Andy explains how to use Category Cabling camera control including the various pin-outs required for camera control. Finally, we review the different baud rate options for joystick and camera controllers. Andy is the lead support technician for PTZOptics and he asks users to submit a ticket or call the PTZOptics 1-800 phone number with any technical questions.
RS485 Camera Cabling
More on PTZ Camera Control & Software
More on PTZ Joystick Controllers
Using SONY PTZ Joystick controllers with PTZOptics cameras here
Video Transcript
Paul: Hello everybody Paul Richards here with PTZOptics
Andy: Hi everybody I’m Andy Johnfield I’m the tech support here at PTZOptics
Paul: Today’s text for Tuesday so we’re going to go over the difference between RS 232 and RS 485 but before you do that just wanted to mention, yesterday on our Monday blog we talked about the difference between You Tube and cable TV, two technologies that are starting to become a little bit more interesting so take a look at that blog and then this Friday our live stream is going to be we’re going to giving away a ten thousand dollars to charity live on You Tube at eleven A.M. two P.M. Pacific. So let’s get started Andy
RS-232 vs RS-485 Cabling
Andy: Yes so just like Paul said we are just going to talk about the differences between RS 232 and RS 485 and a little bit of RS-422 as well and the cameras don’t do that. So why use, what is 232, what is 485, what are the differences, why do you use one over the other. Basically RS 232 is the standard for serial control in this industry. It is consists of essentially three cables transmit receive and ground, are the most important there are other things different forms of the protocol that have other things built in, but for the most part it’s received transmit and ground. This means with 232 you have two way communication between device A and device B. Where device A can [00:02:00] talk to device B and device B can talk back to device A.
A guy said 232 is just the standard has been around since 1962 and it is very widely used the DV 9 connector goes right along with it, that has been used universally in this industry so. With that being said the cameras also do 485 some people are asking well when-when should I use 485 or why would I use 485? 485 is actually a one way communication so device A can talk to device B but device B can’t talk back to device A. It works in a lot of situations where you don’t need the device to provide feedback to the first device, which is like the PTC cameras that we have. We just need to issue commands to the camera and have the camera pan tilt zoom and we’re good to go.
So one of the main limitations between 232 compared to 485 is you can get about forty times the length out of 485 as you can out of 232. It also means there’s not as much information flowing down the RS 485 but the cameras don’t really utilize the entire spectrum of bandwidth that the serial connection can supply anyway. So with 485 it’s actually a lot more versatile.
With RS232 the cameras come with this little cable, and it’s just a DV 9 connection here to the eight pin mini den in the fits in the back of the camera here. This is it’s very nice and easy to use but if you want to extend this you basically have to make a DV 9 male the female cable or a DV 9 female to eight pin mini den to the exact length you need which can be a pain.
I’ve talked to a lot of clients who want to utilize cabling already existing in their walls like cat cables and stuff, to achieve control of the cameras via serial. Which case using 485 is actually really easy, you can cut a cat cable [00:04:00] that goes from point A to Point B just use two of the connections inside the RS 485 is plus and minus, just do 485 plus and minus to 485 plus or minus on the back of the joystick. And you’re up and controlling your camera.
So it definitely makes things a little easier being able to not use proprietary cables not having to buy additional cables you can just use standard cat cable or a like 22 to 22 gauge to channel cable and you can control your cameras all day long.
A lot of people well why should I use 232 then? There are a lot of devices that take 232 and don’t take 485. That’s a pretty common thing to do like I said 232 is the standard in this industry so that’s why the cameras have both.
I did say would mention RS-422, RS-422 the cameras don’t have, but it’s basically just a two way form of 485, it’s the exact same limitations exact same distance lengths, you just have transmit plus or minus and receive plus and minus so you be able to talk between two devices.
As far as hooking up for the cameras RS 485 is golden as far as I’m concerned it’s very easy to set up it’s very reliable it works.
Paul: Now for cascade for cascading that would be the same, same type of cable right?
Andy: Yeah for RS485 you want to cascade you just get another piece of cable go directly in when you plug in the first one I have a little two two pin connector on the back of my camera just put two cables in there instead of one or four instead of two if you want to look at both sides and you can just run your second camera as long as you ID them correctly you’ll have no issues
Paul: Gosh so those two plus and minus there you’d actually put in
Andy: Two cables you have I have one red and one black in that two four connector you have two red and two black, one going back to the joystick or one set going back to the joystick in the next set going to camera two
RS232 Camera Cascade Cabling
Andy: Which is very easy to do and you don’t have to buy proprietary cables like the 232 requires [00:06:00. So I do want to mention if you are using 232 we do have a specific cable there are specific pin outs that we require for first the cable going between the joystick and the first camera you can see that’s the camera to PC Connection and theoretically all you would really need on the computer nine pin side, is two three and five receive transmit and ground. Those are the pins that you need and where they match up on the other side which would be transmit in receive in and ground, that’s all you need essentially.
For the cascade cable this would be the cable going between camera one camera two for RS 232 you do need five cables you need pin one to go to pin two on the other side, and pin two to go to pin one on the other side, and then three in five swap, and four stay straight through, as you can see from that that picture of the camera cascade cable.
So I’ve had a lot of people call me and say they have a male to male eight pin mini den connection and they’re just not getting control be on the first camera, and once we sit down and get them going with the multi-meter they’re able to pin it out they realize that that cascade cable does not have the right pin out.
So that is one good way to double check and see if it’s wired correctly, get a multi meter set up for just testing continuity, and hold it up to pin one on one side and then go through the other pins on the other side, see where pin one lands to the land on Pin two, you’re probably good, check pin three is that when open five, you’re probably good as pin four go all the way through, you’re definitely good if any of those are different you’re probably not going to achieve camera control of the second camera.
So it’s always a good idea to just pin out cables if you have a multi meter handy, if you don’t it’s a really good idea buy one there twenty bucks to have one handy, and if you’re installing the cameras. It can definitely help if-if you’re running into control issues.
I’ve known a few people who they got a cable to short so they just connected another cable to the other side. And the pins swapped every time you transmit and receive swap, so once they added another cable to the run it didn’t work correctly. [00:08:00]
So you have to keep in mind that each extension is going to swap pins two and three and you need them to be a certain way at the joystick end so.
Paul: So last question then for me would be barred rates could you explain that a little bit?
Andy: Yes so basically a barred rate is, takes into account the amount of information flowing down the cable, as well as the cable length, so a lower barred rate you can go further, but you can get less information traveling. And it would be the opposite for a higher barred rate you get shorter length but more information
Paul: Got it so that’s right here as you guys can see
Andy: Yeah we always recommend just staying at 96 hundred barred rate
Paul: That’s the default
Andy: That’s the default that’s you shouldn’t run into any issues with the cameras as long as you’re running at ninety six. If you start going down to forty eight and twenty four certain commands might be missed stuff like that.
Paul: Okay is that everything
Andy: I think that’s it, if you guys have any questions different who excuse me and definitely feel free to post a ticket on PTZOptics dot com. You can post a ticket from the knowledge base or right next to the knowledge base there is a submit a ticket button. So definitely if you have any questions if you are running into issues like this yourself, if you have a scenario you just want to run by means you my thoughts are definitely put in the ticket. I’ll be happy to answer any questions you guys have
