I think it will work, it’s just an on/off accessory so you won’t get dimming from the accessory switch. But I just don’t know for sure if the Eaton master switch will accept the on/off command or if it expects a dim level command.
Before doing anything else, if it was me, I would contact Eaton support and ask them what will happen if you use that accessory with their dimming master switch. 
I already did that. I initially bought the CORRECT switch (the RF9642) and could not find out how to associate it with the RF9640-N. I spent a frustrating hour or more with their techs, and they told me to contact SmartThings, they don’t support it. I went as far as speaking to a manager to tell them “works with SmartThings” is inappropriate if they don’t support making it “work with SmartThings”. That’s when I returned all my “companion” switches. I used hard-wired toggles for the non-dimmable switches, but I found the dimmable one has no traveler wire and does not support hard-wired connections.
After realizing their switch was my only option, that’s when I went back and mistakenly bought the RF9617. Since I don’t care about having a second dimmer control, that’s why I’m asking if I can associate this switch with the master (RF9640-N). But Eaton does not support their product in any way that I can tell. It’s unfortunate, because the switches seem to be high quality.
So that’s correct, one dimmer (and automation) is enough.
I’m game to try it, but I’m lost on the instructions. I figured out what “IDE” is, and I’ve installed the Z-Wave Tweaker, but I’m still pretty lost. The Z-Wave Tweaker doc repeatedly refers to “tiles” but I can’t find anything in the mobile app that resembles them.
Jack
And since Z-Wave Tweaker broke my automations (that was expected), how do I remove it? I can’t now, because “DeviceType still in use by devices”. The Z-Wave Tweaker doc says:
Cleanup Tile:
Tap this tile when you have finished using the Z-Wave Tweaker. It will remove all collected data in preparation for reinstating the original device handler.
I don’t see any “Cleanup Tile” (or any tile, for that matter), or anything about Labs or Z-Wave Tweaker in my mobile app.
Jack
You are only intended to use the Tweaker for a moment in time while you reconfigure the device you assigned to it through the IDE.
As soon as you complete that configuration, you should manually reassign the device to its original DTH.
So if your Routines did stop working, it would only be for the brief period of time while you were reconfiguring that device and they would be restored once you went back to the original DTH.
You are correct that the “cleanup” process is no longer needed: that was used with a previous version of the app.
Speaking of which: are you using the version from post 209 in this thread? Not the original version? (See the topic title). There were several required revisions when the ST app received a major update.
Also, in your case you would only use the tweaker for the trigger device, in this case the accessory switch. Not the target (the master).
I
I got the code from SmartThings/devices/zwave-tweaker at master · codersaur/SmartThings · GitHub, not from post #209. It is:
Since I thought the Tweaker would do its own cleanup, so I did not make note of the original DTHs that were assigned. Is there a way to retrieve that info? My mobile client has an “ORIGINAL SETTINGS” section, but it appears empty.
I have been ill for a couple of days. I intended to write a post for you explaining what the tweaker does for your specific devices, but that’s going to have to wait until I feel better.
I’m sure all this feels very technical and overwhelming. The fact is that smartthings gives us many fewer tools than a typical Z wave hub. Most of them just have a screen for each device which lets you quickly set it up to control another Z wave device. All you have to do is select the device to be controlled.
Smartthings doesn’t. They appear to have made a design decision back in 2013 that they would hide any protocol – specific features from the end-user so that a Zigbee device would look just like a Z wave device. That’s the whole reason you need a DTH to begin with: it’s a smartthings-specific construct that they’ve laid over the independent third-party specifications.
Over the years, several device manufacturers have become frustrated with this whole idea because it means that their certified devices which work just fine on most zwave hubs don’t work on smartthings without special code used only for smartthings, and smartthings keeps changing how that special code works so it has to keep being updated. So the manufacturers have two choices: they can hire somebody whose job it is to keep up with the smartthings-specific changes, as Zooz and Inovelli have, or they can throw up their hands and say “we are certified to the independent third-party specifications, and anything else is the responsibility of the hub manufacturer” as Fibaro has done. And from your description, it sounds like that may be the direction that Eaton is going as well.
It’s very frustrating for us as customers, but it is understandable from the manufacturers point of view. And it leaves us as a community trying to help each other.
Thanks,
Now I see there’s a later version – the scroll bar says it’s post #205 (not 209) but the actual html target is #209. But I found it anyway:
Since I have devices using the Tweaker, I can’t remove or update it.
“Technical” is not a problem. I’m a Unix Engineer by day.
Having to jump between multiple sources (Github, forum posts, etc.) and then decipher unfamiliar jargon (IDE, groovy, DTH, blah blah blah) is pretty challenging, though.
Thanks for your help. I hope you feel better soon. But if I can’t get this solved today, I’m considering returning these switches to Lowe’s and replacing them with the Leviton switches that use travelers. I wish I’d bought those in the first place. Fortunately, Lowe’s is pretty good about returns.
Unfortunately that’s the wrong code. What happened is that the original author stopped using smartthings and moved onto a different hub and no longer maintains his code.
When smartthings made major changes, as they usually do every year or two, another community member stepped up and created a new version, which is the one linked to from post 209 in the tweaker thread.
As for which DTH they would have used originally, the best thing would be to create a new topic with the title
“Best DTH For Eaton 9540 Master Dimmer and RF9617 Accessory?” and hopefully someone who currently has those devices working will respond and can tell you what DTH they are using.
The following community FAQ is very old and the examples are out of date, but the concepts and terminology are still current and should help. The topic title is a clickable link.
Groovy is a programming language, like Java, Lua, Python, PHP, etc. It is not a SmartThings construct, it’s just the language That the original smartthings developers chose for their platform. However, smartthings is in the middle of a major architecture change, and support for the free groovy cloud from smartthings will be discontinued soon.
The new equivalent of device type handlers are “edge drivers“ which are written in Lua and will run on the smartthings/Aeotec hub.
Some power users may choose to continue using groovy and they can, but they will have to host it themselves and then communicate with their smartthings account through the API.
Other power users have chosen to go to a competing hub, Hubitat, which also uses the groovy language but runs everything locally, no cloud.
Also, I forgot to say that, yeah, if you can use physical traveler wires, the Leviton devices might be a better choice. Because the Tweaker is one of those groovy DTHs that will stop working pretty soon. And then I have no idea how you will set the parameters in the future. It was honestly kind of astonishing that the community had to create the tweaker to begin with.
Sorry, I edited the previous post while you were replying.
But yes, some of this I’ve figured out. It just took some time. This whole experience illustrates exactly why I DIDN’T select Hubitat, and tried but abandoned Home Assistant platforms. I did not want another hobby or job. My expectation was that “Works with SmartThings” meant what it said. I had a similar issue with Z-Wave Honeywell thermostats, but I got them working (or Samsung did). But I know, I’m preaching to the choir. It’s a shame, the Eaton devices are solid.
Ultimately, I don’t want to be a “power user”. I just want things to work. 
I’d love to see everything moved to local control (à la matter), but I still don’t care to know “how the sausage is made”.
Oh, yeah, sorry about that. I am quadriparetic and use voice software to dictate posts. Which means I have to do a lot of editing to correct errors from the dictation. So my posts usually go through multiple revisions before they’re done. (It’s also the reason you’ll see random capitalizations in my posts. If I pause for any reason, the dictation program will think it’s a new sentence when I come back.)
As for “just works“ smartthings has always been pretty, But never quite seemed to understand the “works out of the box” concept. They are a certified zwave hub, but then they put this extra abstraction layer on the top of it which breaks a lot of things or hides a lot of features. Out of the box you should get a basic on/off but anything other than that often ends up requiring more work than it should, IMHO of course.
I personally switched all my own critical use cases to Apple HomeKit A few years ago because in my situation I need very good reliability that lasts. What engineers call MFOP (maintenance free operating period). But I still use ST for some of the fancy stuff you can’t do easily on platforms that don’t have customization options. And I have hope that Matter will help once it does arrive. We will see.
I edit and re-edit just because I don’t like what I’ve typed, or I left out something I thought was important, or after cooling off, it doesn’t sound so good.
But your responses are too fast for me, so I’ll try not to do that.
I changed the DTH for both devices just so that I could update the Tweaker. That worked fine, and I see some nice new options and functionality. I removed the “companion” switch, re-added it, and attempted to associate it with the master switch. I am sure I selected the appropriate association group and the device ID of the master switch. Then I did the cleanup (it retained its associations), and reassigned it to its original DTH (having made note this time).
The IDE (and my iPhone app) show the companion switch as “connected”. The IOS app does not have a power on/off switch, but shows the state as “off” or “on” appropriately. The LED indicator on the switch agrees (powered on vs. powered off). However, nothing happens to the lights. Live logging (on both switches) says they’re waiting. So I’m still stumped.
I’m still not convinced that a binary on/off accessory switch will successfully trigger a master dimmer: they use a different set of commands. The master might get the “on“ but lacking a dim level treat it as 0%, so it wouldn’t change the light.
That’s why I suggested asking Eaton support about that since that’s a question independent of the smartthings – specific stuff, it’s just part of the basic Z wave specification.
You can even ask them a hypothetical, like “ if I get a vera Z wave hub can I set it up so the accessory switch will control the Master?“ and use your model numbers which I’m too lazy to include in this post.
Because I’ll be honest, I just don’t know if it will.
I forgot to mention that the whole point of Z wave direct association is that the messages go directly from one end device to another, they don’t go through the hub. So I don’t think they’re going to show up in live logging, which is a hub utility unless you also included the hub in the association group.
Understood, messages bypass the SmartThings hub completely.
You raise some good questions. This might just work if I had the right companion switch. But at this point, I don’t want to “try” another switch, and I’m not inclined to deal with Eaton’s support folks anymore. If I have to make just one more trip to Lowe’s, it will be to return my switches. Since I’m replacing a dumb 3-way setup with traveler wiring installed, I’ll just go with the “it just works” style solution – the Leviton combo.
Thanks for your help!
As @nathancu suggested in the tweaker thread, you are using group 2 for this device, correct? not group one?
Group one is the lifeline group and should have the hub and only the hub in it.
Group 2 for this device should have the hub and the master switch in it.
And you have to put the master switch ID in hex, not decimal.
I wasn’t using group 2, but now I am.
The ID for the master switch is “0A”. I assume that’s hex. I put it in that way. Messages from Live Logging make sense. This seems to suggest (as you already mentioned) that this companion switch is indeed incompatible with my master dimmer switch:
d234911e-db73-45cd-87c2-0a42f172b0ae 1:31:05 PM: info Association Group #2 has name: Basic set
d234911e-db73-45cd-87c2-0a42f172b0ae 1:31:05 PM: info Association Group #2 has name: Basic set
d234911e-db73-45cd-87c2-0a42f172b0ae 1:31:03 PM: info sync(): Unknown association group. Requesting more info.
d234911e-db73-45cd-87c2-0a42f172b0ae 1:31:03 PM: warn sync(): Device does not appear to support ASSOCIATION or MULTI_CHANNEL_ASSOCIATION command classes.
d234911e-db73-45cd-87c2-0a42f172b0ae 1:31:03 PM: info Endpoints [0]:
As for the Hub device ID being it that group, I don’t know if it is or not.
It makes me angry that I HAD the correct companion switch, but returned it and eventually bought the wrong one. I’d love to “win” this, but I really need to just be done with it. If I return the wrong switch, buy the right switch, there’s still no guarantee I can get it to work.
On the other hand, if I just return them and replace with Leviton, it’s a pretty sure thing.
Not sure if I should create a new topic or ask here. I made the mistake of removing my accessory switch and when I added it back, I think it now has the edge driver from my researching the last few days. Is there anyway I can associate the accessory switch back with the master switch?
Tricky. 
I just don’t know what can be done in that particular set up. maybe @Automated_House has a suggestion?