A question about Zigbee Channel Scan?

[jtmpush18]

Does this show only Zigbee channels (and not 2.4 WiFi)?

In terms of RSSI, is it true that the greater then negative value, the stronger the signal?
According to the wifi analyzer program that I have:
Good: -60 -> -40
Medium: -89 -> -60
Poor: -100 -> -89

[Tony]

No, your wifi analyzer table is correct; the more negative, the weaker the signal; but since the scan only measures RF energy in Zigbee channel bands, it can't distinguish signal from noise (or an overlapping wifi sginal )at the time of the detection.

[alex1]

I find it strange the C-8 zigbee channel scan reports rssi and lqi with the transmitter on. For example, if I turn up the TX power, rssi and lqi drops.

If we are doing a channel scan, shouldn't it be doing so with the transmitter off and analyzing things from a receive only point of view?

C-7 seems to do what I expect. C-8 does not. bug??

update: here are the channel scans for comparison between a C-7 and C-8. C-7 and C-8 are both online in the same utility shelf. C-7 is using channel 11. C-8 using channel 25.

[Tony]

@alex1

If we are doing a channel scan, shouldn't it be doing so with the transmitter off and analyzing things from a receive only point of view?

Zigbee radios are half duplex so are either in transmit or receive mode (but not both simultaneously); also they're capable of doing two kinds of scans-- both types are done by a coordinator when it auto selects a channel to initially form a PAN: an energy detect scan (receive only, where it's looking for the quietest channel regardless of signal or noise content) and an active scan, where it's detecting other established PANs (to pick the channel with the fewest active networks). In this case the radio's alternately transmitting and receiving-- sending beacons and then listening for beacon replies from already established PANs. HE's scan report is evidently the result of active scans.

There's a good description here: ZigBee applications - Part 3: ZigBee PANs - EE Times

[alex1]

Thanks the background. However, take a look at the two screen shots differences between what the C-7 and C-8 shows.

[Tony]

Yes, the scan reports aren't consistent and (at least for C-7 and C-3) extended PAN id's are reported in the wrong 'endian' format (C-8 gets them right). And sometimes nothing shows up.... I reported the differences I've seen here:

Zigbee non-functional, but shows Online

Lol... weird. There was one recent beta where my C-8's scan never showed anything; the next beta 'fixed' that (except for not showing itself). At least C-8 gets all the Extended ID's formatted correctly (when it decides to show them): Here's the channel scans produced by my C-3, C-7 and C-8=; only the C-3 shows all three HE PANs C-3 scan: [Screenshot 2023-11-30 152322] C-7's scan: [C7 scan] C-8's scan: [c8 scan]

AFAIK these quirks haven't been commented on by anyone in the know.

[alex1]

My expectation, as a customer, is the Channel Scan tool is supposed to be used to help finding a clear channel to use and set the zigbee radio to the channel with the least amount of noise and/or interference. If that's the case, then what I am seeing with the C-7 is right. What I am seeing with the C-8 will just generate customer support questions IMHO. Like, "why does the lqi and rssi get worse on my own channel when I raise zigbee TX power? " IMHO, this is a bug specific to the C-8. cc: @bobbyD.

[garyjmilne]

@alex1

My expectation, as a customer, is the Channel Scan tool is supposed to be used to help finding a clear channel to use and set the zigbee radio to the channel with the least amount of noise and/or interference.

Ditto for me. Just migrated to a C-8 pro and none of my Zigbee devices were working. I turned to this tool to give me more information. Now, because the table is empty, rather than narrow my scope of troubleshooting it has widened to "does my Zigbee radio even work".