Recently I was forced to rebuild all of my groups. A daunting task - the result of legacy I guess.
I'm really looking for a useful overview or guide of someone experienced with Zigbee (both legacy and 3.0) who's recommendations I can follow. My hopes for information are about these settings:
Groups now have a number of settings which I'm unclear of their specific functions and therefore I'm guessing at when and how to use them. Zigbee Group Messaging - It seems obvious but many but not all of my groups failed when I enabled this. In the end I turned it off for all groups - is this Zigbee 3.0 specific? is it similar to On/Off Optimization? Group Activation device - Bulb, Dimmer, Switch. - While again this seems obvious, is it recommended to use Dimmer for dimmable bulbs or is that just for switches? Should I use bulbs regardless of CCT/Dim/RGBW? Show Group State in Group Device - I've turned this on for all groups but I've no idea what it is for. Command Mixed Devices: Do I enable always? if it's a group of 1 device, it seems I wouldn't need it but is it for when there are different selections in the drop downs? Enable On/Off Optimization: Is this device specific? or Zigbee 3.0? It has only worked in a small subset of devices and I now just always disable. Enable Metering: When this first came out it solve a ton of my problems. I've learned that I setup small delays for all groups depending on their distance from the hub has been my best result. Has anyone created guidelines on when this is helpful or not? The popcorning effect has not been a bother for me, at least all my bulbs go off and on!
Zgm is a multicast filtered broadcast. It is a single send that is filtered to only the Zigbee devices in the group. It can be routed through repeaters, but should be less traffic than sending separately to each device. This is zha and zll compatible.
On/off optimization checks the state of each device and doesn’t turn on/off devices that report they are already in that state. I only use this for z-wave devices since it’s easy to overwhelm a z-wave network, not sending unnecessary commands is helpful when turning multiple devices on or off. It won’t work well if devices don’t report their state reliably.
This I believe was differentiated for limiting what capabilities show up for devices shared to a voice assistant such as Alexa. Bulb has all capabilities including color/ct; Dimmer has dimming and on/off; Switch has only on/off capabilities.
This just shows the “on/off” state of the group. Look at the group device page and turn one light on, then all lights on, and you should see this change to reflect that.
The option allows for mixed device control, where setLevel for a dimmer will turn on switches in the Group.
The Groups documentation documentation was just updated (literally seconds ago) with this information, so hopefully that is helpful for anyone who finds this in the future! But to directly address your questions:
Zigbee Group Messaging is not 3.0-specific and should work with any Zigbee switch/dimmer/bulb, though I wouldn't be surprised if there were some oddballs that didn't support groups (I don't know if Hubitat's implementation waits to hear back from the device to see if it got added to the Zigbee group or just assumes it does, but hitting "Done" in the group app will make it try again, so if anything failed--or if you have reset the real-world device for any reason--that may help); presumably they have this option in case your devices don't work with it, though in my experience it's normally better
Group activation device: this affects what capabilities (commands and attributes/states) you see on the device page. If your group contains only switches, you probably don't want "bulb" because then you'll see things like "Set Color." Similarly, perhaps you have a group of bulbs but only care about level and on/off, so you could override the default selection and choose "dimmer" here if you wanted. (Back in the day, everything was a "bulb," which some people didn't like because even making a group of just switches would show color and level commands.)
Show group state in group device: This adds a groupState attribute to the group device page under "Current States" and will be allOff, someOn, or allOn, which I assume was either something they thought of or something someone asked for to know more than just the on/off state of the group itself does (according to the other options you can choose)
Command mixed devices was added in response to this thread: Groups with switches don't turn on by setting level - #35 by bravenel. Devices like switches don't support "Set Level," for example, but "Set Level" normally turns on a dimmer (or bulb). Enabling "command mixed devices" will cause the Group to simulate this behavior by sending an "On" to a switch-only device when you send a "Set Level" to the group. (Similar for "Set Color" and "Set Color Temperature," which conventionally also turn on a device.)
On/off optmization: not Zigbee-specific, just looks at the member devices and doesn't send a command intended to change its state if the device already reports as being in that state -- so if a member bulb is already off, it wont' send an "off" command to that device when you tell the group to turn off, for example. (IMHO this normally causes more problems than it solves, but it might be more useful for Z-Wave devices that do reliably report state and where your network might like sending as few commands as needed.)
Metering: sounds like you've figured this out--just inserts the specified delay between commands (if you have Zigbee group broadcasting enabled, I assume it doesn't do anything if all devices are in the group)
I used to have to do this frequently when I had groups of Osram bulbs. It would help for a little while. The IQ Zigbee chip they used was for irony I think. Fortunately the bulbs all went bad (they seemed to overheat and would become unresponsive) and were replaced with the Ledvance version.