Testing the “STW can answer anything” mantra to its limits here I think, but here goes.

We’ve got a multi-screen video wall at work, and anyone who ever knew anything about it has long since left the company. Frankly, it gives me the fear. The server controlling it has sixteen(!) DVI connections, most of which disappear off into the wall, making cable tracking a nightmare.

Anyway. We want to repurpose it and it’s fallen to me to unpick how it works and what’s going on with it. One thing I’ve spotted is that each display has two 8P8C (RJ45) connections labelled as RS485 In and RS485 Out. I’d never heard of RS485, but a quick Google tells me is for multi-point communications. These are daisy-chained together, and as far as I can tell they terminate in some sort of serial-to-USB adapter which is plugged in to… nothing whatsoever.

So the question is, has anyone come across this sort of setup before, and can give me some insight into what it’s actually likely to be for? I’m assuming it’s some sort of remote control for the displays but I’m speculating at best. It’s clearly not critical as it can’t have been plugged in for a year or more.

I’m half tempted to just plug it in and see what happens, but the last time I tried something creative with this server the display driver exploded and it took me the best part of an hour to set the screens back up again.

Cheers.

Can you find a data sheet for the TV’s? You will need the correct buad setting etc to get any thing to work.

Other than a remote control could it also be giving some kind of sync sygnal? In which case there may be sort of calibration routine that assertains the delay between each node from a master clock syngnal and then updates any error in a local clocks depending on their position in the chain. (Ethercat uses this type of method)

Good idea, I’ll have a rummage. (Why didn’t I think of that?!)

Sync makes sense, so if you’re running video across them you don’t end up with different lag across the displays, that sort of thing you mean? So presumably a) it might be enough just to plug it back in to the server and hope it Just Works and b) the images we’re showing are broadly static (they’re web pages) so it’s probably not needed in our case.

Ta.

Found a datasheet, but I’m no nearer.

http://www.eyevis.de/files/eye-lcd-4200_datasheet_en_v1.5.pdf

Might be a call to support at this rate. Ugh.

I’m assuming it’s some sort of remote control for the displays but I’m speculating at best. It’s clearly not critical as it can’t have been plugged in for a year or more.

Seems likely to me – it might be to allow one display to be the “master” that receives inputs from the user (via remote control or buttons and on-screen display) and then send them to all the other displays.

But I’m afraid I’m just guessing like you.

The webpage says it features:

Network-Based Features
– Remote monitoring & diagnosis function
– Scheduling & administration of content
– Remote power on/off
– Remote stand-by / power save mode

So could be related to that in the same manner. One display is connected to the network and communicates with the rest.

Ooh, you might have a point there. They’ve always been temperamental when using the remote (and I never stopped to think that the problem of having one remote and nine displays might actually have some sort of sensible solution), when the power’s gone out historically I’ve wound up having to switch them all back on with a pool cue up the back. Remote power-on would be a handy thing.

Those aren’t quite the same screens (I think they’re LED and ours are LCD) but I guess the principle is the same. They boast “1× RS232 (full remote control and service)” so presumably what we have is of a similar ilk.

Not that it helps you much, but RS485 is simply an electrical spec for bus connection of multiple devices. Doesn’t specify anything about data protocols to be used – though typically I’d expect to see asynchronous protocols as used in RS232 at a bit level (ie start bit, 8 data bits, stop bit) and some sort of bus protocol at byte level, with the first byte having a master/slave bit and an address in the other 7 bits. If it was connected I’d use a data analyser to check what the protocol is…

You’d typically use RS485 rather than RS232 for connecting multiple devices – RS232 (or RS422, which IIRC is more similar electrically to RS485) is for point to point only. Hence whey they’re using that. My money would also be on something as simple as on/off.

Aye, that’s where I came in to this conversation. I Googled RS485 and pretty much found what you’ve just said, it was akin to searching for USB to work out what an unidentified dongle is for.

Waaaaayyyy back (20+ years ago), I used to have a bunch of dot matrix displays showing call centre stats. These were LED displays and RS485 was what we used to connect them together.

It was always a bit of a cobbled together type of operation, not least because it took a few hours one afternoon with a breakout box and soldering iron to get the right pin outs on the D9 connector. It actually lasted quite well, but I wouldn’t really want to set one up now. Your LED displays must be ancient now, but if not, you may be able to retrofit with IP modules, which makes things a lot easier.

Other than that, the very best of luck getting your museum piece working!

EDIT – the unidentified dongle – could it be an old fashioned ‘license’ dongle? That would explain why it’s plugged in, but nothing on the other end

They’re not that old! The video feed is HDMI, the RS485 is Something Else </Oliver Queen>.

The RS485 / USB bit should attach to a scaler/programming unit.

That tells the matrix how the screens are wired (i.e. in what order) and also usually auto scales any HDMI input to itself to the screen configuration.

In general the screens ‘know’ the configuration, but if it goes t*ts up, you mgiht need to connect the controller to re-blow the configuration down.

I have something similar at work, I can get some brand names etc. from the AV rack if it’d be of help?

At a guess, the RS485-USB adaptor would be used to plug into a PC to allow the screens to be setup, but wouldn’t normally need to be used during everyday operation.

However, reading brassneck’s post I wonder if these displays would do the scaling of the image themselves, or whether the PC they are connected to would do the scaling before sending out the image.

However, unless you can get some software from the suppliers, a programming unit, or a far more detailed manual describing the protocol used you are going to be in trouble, as you can stream pretty much anything over RS485… TCP, Modbus, or even some homebrewed system that they thought up on a Friday morning!

That tells the matrix how the screens are wired (i.e. in what order) and also usually auto scales any HDMI input to itself to the screen configuration.

By nature of where it is, the only thing it could attach to is the display server or to a PC which is used as a display source. Or, I suppose, the laptop of a passing engineer.

The control software gives you the option to describe the screen layout (it’s similar to the Windows multi-screen configuration panel). I assumed that then just assigned screens based on which ports they were physically connected to. Ie, I can’t see why the screens would need to know where they were, because the server does. Or something.

EDIT: unless what you’re saying is, that’s pish and you could just connect them any old how and use the RS485 comms to assign numbers to screens. That’s far more sensible. (Though I do wonder now that if I plug in the USB it’ll renumber them all…!)

Shared config makes sense though. Again, like with the remote control, I can see the logic in not having to set up contrast, brightness etc manually on multiple screens. I wonder if there’s a tool I’ve not yet found on the server which does that? That would be the missing piece of the puzzle if so.

Hmm. Food for thought. Cheers all, very helpful.

At a guess, the RS485-USB adaptor would be used to plug into a PC to allow the screens to be setup, but wouldn’t normally need to be used during everyday operation.

Aye, I was just wondering that myself. And of course, disconnecting it prevents curious systems engineers from frigging about with things they don’t fully understand…

However, unless you can get some software from the suppliers, a programming unit, or a far more detailed manual describing the protocol used you are going to be in trouble,

<nods> to be fair, this was less “how can I use this interface to hack the screens” and more “ooh, what’s that for then?”

chicken

@cougar I have seen the Eyevis system before, just out of interest could you tell me where the site is located you are at, I have the contact details of a guy there is you want to PM me.

The RS485 will be for the Eyevis controller to tell the screeen what to display where from its inputs.

As above. The HMI is doing all the “heavy lifting” (ie the actual picture data transfer) the RS485 can only be for set up or remote control of basic parameters because it is not a fast enough bus architecture to do update any significant display RAM etc!

I’m sure the RS485 will be using a basic serial protocol (8b,1Stop, zero parity etc) and the interface details must be specified somewhere by the screen manufacturer!

I have seen the Eyevis system before, just out of interest could you tell me where the site is located you are at, I have the contact details of a guy there is you want to PM me.

We’re in Burnley, which conveniently is where Eyevis UK are too.

OK, we did a job in Manchester where our system was put onto an Eyevis system, they are decent guys from what I remember,

Didn’t get into the nitty gritty of the control of the system, pretty sure most of their later systems are Video over CAT5 and IP based for control anyway.

Yeah, I think ours predate that, looking at the stuff that’s on their site now.

Didn’t get into the nitty gritty of the control of the system, pretty sure most of their later systems are Video over CAT5 and IP based for control anyway.

That’s what ours is. Sounds like this is the previous generation.

EDIT: Just read the bit about server / 16 HDMI connections – the cable pattern is indeed then less relevant, as ours are daisychained and can be done in a couple of patterns. Selecting the wrong output config mixes it all up like one of those slidey square puzzles.