Zigbee channel change, certain devices will not pair back

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1

So I swapped Zigbee channels,3 days ago, on my C4 & C7(both latest firmware) moved the C7 from ch20 to 25, moved the C4 from ch25 to ch20. The C4 seems to have responded fine and most devices reconnected. However on the C7 it will not re-pair devices that were previously connected. The devices are a Sylvania Contact Sensor and a Sonoff SNZB01 button, both are supported devices. I have shut down the C7, pulled power for 20 seconds and restarted. Also totally shut down hub for 40 minutes. Also tried a soft reset, no luck, the hub refuses to see these existing devices and pairing in general is problematic.

As a test I was able to rapidly pair these devices on the C4(left them on the C7-didn't unpair the device) after a factory reset of device. So the devices are properly functioning. Before the channel change all devices were solid on the C7. Wifi is channel 1 hub, well CH25. Everything was solid on both hubs prior, all the same devices. Now 2 more rogue devices that won't repair, an ecolink bulb and a Sylvania smart bulb. I have 4 iris plugs and 2 Xbee's, and 2 Tuya micro repeaters, centralite plug and 2 sylvania plugs(too many repeaters?)
And not sure if related but the C7 has a DB swelling issue. After soft reset the DB is around 17mb, but within 4-8 hours the DB grows to 55-65mb.

Also have a null entry, just noticed. Could there be a bug with channel change functionality?

Summary

Parent child parameters
EzspGetParentChildParametersResponse [childCount=1, parentEui64=0000000000000000, parentNodeId=65535]

Child Data
No information for Child 0

Neighbor Table Entry
[Syl Bulb Hall 3, 0941], LQI:252, age:3, inCost:3, outCost:1
[Thermostat Sinope, 218B], LQI:255, age:4, inCost:1, outCost:0
[Syl Hat Loft 3, 227B], LQI:253, age:4, inCost:3, outCost:1
[Plug Samsung Porch Left, 2BFF], LQI:254, age:3, inCost:1, outCost:1
[XBEE3_UFL_ADTN, 4952], LQI:254, age:4, inCost:1, outCost:1
[Repeater Zig 3 Addition, 69A9], LQI:253, age:4, inCost:3, outCost:1
[XBEE_PRO_3_PC, 77C8], LQI:255, age:7, inCost:1, outCost:0
[Enerwave Zigbee Plug, 81D3], LQI:252, age:4, inCost:3, outCost:1
[Repeater Tuya Porch, 9475], LQI:254, age:4, inCost:1, outCost:1
[Plug Iris Addition, 9A3B], LQI:254, age:4, inCost:1, outCost:1
[Syl Bulb Hall 2, ABE4], LQI:254, age:3, inCost:1, outCost:1
[Plug Iris Closet Kitchen, B0D2], LQI:255, age:3, inCost:1, outCost:1
[Syl Hat Addition 1, CA2D], LQI:255, age:2, inCost:1, outCost:0
[Plug Iris Porch Left, E6E1], LQI:255, age:3, inCost:1, outCost:1
[Plug Iris 3210L Basement Stairs, F4B3], LQI:254, age:3, inCost:1, outCost:1
[Syl Hat Library 1, FD95], LQI:255, age:2, inCost:1, outCost:0

Route Table Entry
status:Unused
status:Active, age:64, routeRecordState:0, concentratorType:None, [Water Dishwasher Flood ADT, 49AD] via [XBEE_PRO_3_PC, 77C8]
status:In Discovery, age:0, routeRecordState:2, concentratorType:High Ram, [null, 0000] via [XBEE_PRO_3_PC, 77C8]
status:Unused
status:Unused
status:Unused
status:Active, age:64, routeRecordState:0, concentratorType:None, [Motion Front Door Stairs, 9FDE] via [Enerwave Zigbee Plug, 81D3]
status:Active, age:64, routeRecordState:0, concentratorType:None, [Door Front 🚪, A942] via [Plug Iris Closet Kitchen, B0D2]
status:Active, age:64, routeRecordState:0, concentratorType:None, [Motion Front Door Hue, C4E3] via [null, 4EB3]
status:Active, age:64, routeRecordState:0, concentratorType:None, [Motion Garage Temp/Humid, 2EBD] via [Repeater Zig 3 Addition, 69A9]
status:Active, age:64, routeRecordState:0, concentratorType:None, [__Hue dimmer Rule Basement, B400] via [Repeater Tuya Porch, 9475]
status:Active, age:64, routeRecordState:0, concentratorType:None, [Thermostat Sinope, 218B] via [XBEE3_UFL_ADTN, 4952]
status:Active, age:64, routeRecordState:0, concentratorType:None, [null, CDE7] via [null, CDE7]
status:Active, age:64, routeRecordState:0, concentratorType:None, [Hue V2 Dimmer, 8207] via [Thermostat Sinope, 218B]
status:Active, age:64, routeRecordState:0, concentratorType:None, [Motion 2nd Floor Hue, BEC5] via [Plug Iris Closet Kitchen, B0D2]
status:Active, age:64, routeRecordState:0, concentratorType:None, [Water Kitchen Sink, 4CFE] via [Plug Iris Closet Kitchen, B0D2]

Yes I placed a ticket but no response within 3 days so thought I'd ask some smart folks I know

2

Some older zigbee devices will not work on channel 25. Channel 25 is also reduced power to comply with FCC requirements. I have had mixed results with zigbee devices on channel 25.

1 Like
3

Many articles that you read about Zigbee channels speak of channels 25 & 26 being restricted to lower power by the FCC. Wording usually looks something like this excerpt from the Control4 Pro Installer manual:

“To select a Zigbee channel that does not overlap with WiFi, try channel 15, 20, or 25. These Zigbee channels avoid the most common WiFi channels (1, 6, 11). Also note that channel 25 in the US has lower transmission power per FCC requirements.”

In articles from Silicon Labs Knowledgebase they make the following statements:

“Band Edge Concerns: The top end of the 802.15.4 channel band (Channel 26 and occasionally Channels 24 an 25 at very high output powers) usually pushes up against the limits of the band, encroaching into the reserved area in the adjacent (higher) frequencies. Therefore, it's often necessary to artificially limit (with software) output power on these upper channels (as much as -9 or -10 dBm) in order to pass FCC TX testing.”

“ Actual channels available vary by country. For example, in the USA, only Wi-Fi channels 1 through 11 are available. Bluetooth channels 0 through 39 are available worldwide and Zigbee channels 11 through 26 are available, although channels 25 and 26 require reduced transmit power levels to meet FCC requirements (North America only).”

“ FCC testing, applicable to U.S. design only, has strict rules about band edge restrictions at the upper edge of the 2.4 GHz band. This does not allow for running at max power on Channel 26 (since even at +3dBm you will bleed too much outside of the spectrum to pass FCC). Also, if your design has external PA's driving +10 to +20 dB of gain, then usually the power will need to be reduced for Channel 25 in order to pass this restriction as well. In these cases (channels 25 and 26) the module manufacturer, or whoever did the FCC qualifications on the RF design, will need to be consulted for what is an approved power range. ”

In addition, it is a fact (and my personal pain experience) that some older Zigbee devices simply will not work or pair on channel 25 and certainly not channel 26.

Digi specifically discusses that some of its older XBee devices will not work on channel 25.

Again, I don’t claim to be an RF expert engineer but what I read from sources, that I generally respect as experts such as Control4, Silicon Labs and Digi, indicate to me that Channel 25 & 26 do operate on reduced power and have some compatibility issues. That combined with my personal experience makes me compelled to use them with caution.

4

Try changing to channel 24. That’s where I have my HE with my Sylvania lights. I have used 20 and 25 for my Hue bridges and 19 and 24 for HE without issues. That’s with WiFi on 2 & 8 (it decided on that itself).

5

I'm sure that you can have at least 16 repeater devices.
When I changed Zigbee channels a while ago, some devices came with the change, and some had to be re-paired.

6

So more info. I have read that only 26 is lower power, but the info from @automation looks very legit, however includes "occasionally" and constraints around when 25's power must be reduced. I think only the HE staff can tell us for sure what is the case. Even if it's lower power, I have many, many Zigbee repeaters~20(i lost track, it's a sh!t ton)
I have used Channel 25 for almost 3 years with very good results. And keep in mind, about 90% of the devices that are on the C7 previously lived on the C4 on channel 25 and worked well. I migrated over about 5-6months ago from C4 to C7. At that time the C4 was on 25 and the C7 on 20. Things blew up when I recently swapped 20<->25, on both hubs, at similar times. NEVER do that.

I think I may have discovered the issue, when I tried to re-pair a bulb back to the C7, that didn't reconnect on channel change, the bulb blinked the "I am paired"confirmation pattern , however the device did not pair back to the C7 where it lived, nor did it show up on the other hub(C4). I thought that's odd. So I shut down the C4, and tried again. As soon as I did that the bulb paired to the C7 immediately. This bulb hasn't been on the C4 in over 6 months, however it was "used to being on 25" <- I have no idea if that's even a thing.

What I suspect is during a channel change, some info is retained causing odd behavior, even after reboot. (The C4 is auto rebooted every 12 hours, due to DB swelling that support has no clue about) This is complicated by changing both hub's channels at the same time.

You know that old saying, "tweak it till it breaks"...they had me in mind

1 Like
7

I have read that Konke devices in particular, play well only on channels 15, 20, and 25.
However, I have never heard any other such issues with any other manufacturer.