# Connecting two PLCs with an HMI build in RS View32 works



## paulengr (Oct 8, 2017)

Kind of the wrong forum. Mr. PLC is a better forum for this.



First you add a driver to RS-Linx that supports the protocol you set up the SLC to communicate in. You should be able to browse to the PLC and check properties, etc., from within RS-Linx, no "red X", etc., if it's working correctly. Usually the first thing to realize is that the PLC is a "DTE" (data terminal equipment" device and so is the PC so you will need a "crossover" type RS-232 cable (pins 2 and 3 swapped). Easiest way to check all this is to get an RS-232 test tool which is a small device with RS-232 jacks on it and red/green lights. Make sure you get a light on transmit and no light on receive on one device and the opposite pattern on the other side (PC vs. PLC through the cable) or they cannot communicate. Then move on to the PC side of things. If you have a newer PC with a "dongle" auto-configure might not work...only certain USB chip sets support it, but try to get one. Then just configure the driver, hit "auto configure" and it should just work, showing your PLC name, no red X in the "who is" network display.


Usually when I'm doing this first I get everything established with my programming laptop. Once that's working then I switch to connecting up the HMI PC and just copy over the settings that worked on my laptop. This avoids most of the problems.



If RS-Linx acts up, delete the "harmony" files (google this). This happens if the database gets corrupted, which frequently happens when you are troubleshooting and moving lots of things around. Then you have to start over putting all the configuration stuff back together...once you have a fully working system, back it up so that you can easily restore it again. In fact before you even start messing with the HMI it's best to at least back up what you have in RS-Linx before screwing with the setup so you can easily get back if Harmony blows up on you.



Then finally over in RS-View 32, a quick history. Basically when you pull up say Logix 500 programming software, it connects to RS-Linx via a proprietary method that Allen Bradley has never published. Among other things, you do not need a license with RS-Linx to use this interface and that's important for you. In RS-View 32, these are called "direct drivers".


The other way RS-Linx can work is via OPC. OPC is a "universal" protocol that allows any HMI to communicate to any PLC driver software and RS-Linx supports that, too. So you can make RS-View 32 communicate with say a Modicon or a Toyo (Automation Direct) PLC as long as you have the driver software (OPC) and the HMI supports OPC which RS-View 32 does. This was done not only to break the proprietary HMI software limitations but also more importantly it was supposed to reduce software costs by eliminating the extra time and money involved in developing software drivers for basically every PLC out there. Now the downside: the OPC Foundation itself is a total 100% rip off. To even use the words "OPC" to advertise your software, you have to pay a lot of money to the OPC Foundation annually and the fees are in the thousands. Even having access to the software development libraries which you'd think would be free since it helps promote it's use is also yet another license fee. Allen Bradley is no different than anyone else. To use RS-Linx with the OPC drivers, you MUST have a licensed copy. The minimum license is the "OEM" version. You don't need the Gateway ($5000+) license. That's only for RS-Linx-to-RS-Linx communication like if you have your PLC connected via serial port to your HMI and you want to be able to simultaneously run Logix 500 on your laptop connected to the HMI via Ethernet. So if you are trying to do this on the cheap, don't waste your time with OPC unless RS-Linx is already licensed.



IF you have the license then go into RS-Linx and define an OPC topic once you have the RS-Linx side working correctly. Then you move over to RS-View 32 and add another "Node" using the OPC driver. If you don't have the license then do the same thing but use the "direct" drivers.


Then with your new node you go into the tag database and start adding tags. Direct tags work but you miss a lot of features (alarms, scaling, etc.) if you try to just start using tags directly in your displays. I've done this many times, but following the 3 step process of making sure the RS-232 stuff is working well, THEN moving on to RS-Linx, and finally HMI is the tried and true way to make things work. When you do get to RS-View 32 start with something simply like watching the "seconds" register in a simple numeric display on the screen. That's about as simple as it gets and ensures everything is working correctly.


When troubleshooting, do the same thing...look at which HMI tags aren't working then go to RS-Linx and look for red X's on the devices that are not communicating. Fix the communication problems first. Then if you've got it all working to this point then it's a Windows thing. Time to 3 finger salute (CTRL-ALT-DELETE, reboot!) Among other things, Windows does not have a concept of a "timeout" so if communications stops then the buffers simply jam up and overflow and software simply inexplicably "hangs". Ever told it to open/close or do something with the wrong file or open a folder on a thumb drive that you just removed and had windows hang for several minutes before you finally get control back? That's the buffer issue that plagues every part of Windows. It's basically bugs and making assumptions that some things in the software/hardware stack don't change but Windows programmers never learn, they just create more bugs. It's OK when you get locked out of saving your spreadsheet but it's quite a different thing when you have a Windows PC running a plant.


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## splatz (May 23, 2015)

priyankagupta said:


> First you add a driver to RS-Linx that underpins the convention you set up the SLC to impart in...


Another translate-untranslate rehash of a previous post by the same user / bot - this time @paulengr 's

I don't know what mischief he's up to, but isn't plagiarism bad enough to ban this user, rather than wait and see exactly what the scam turns out to be?


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## telsa (May 22, 2015)

He's using such a post as self-promotion back in Lahore, Pakistan.

He can link right to just that blurb. Otherwise, it'd have no purpose.

When asked if he typed it, he can 'honestly' say that he did. Heh.


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