Low Transmission Power

[alelucc]

While troubleshooting a problem i was facing, in the configuration.yaml i enabled ZHA logs and i noticed that the radio module was set with a very low Tx power (8).
2021-01-25 09:04:00 INFO (MainThread) [bellows.zigbee.application] Node type: EmberNodeType.COORDINATOR, Network parameters: EmberNetworkParameters(extendedPanId=cc:cc:cc:cc:e3:ab:00:78, panId=0x3498, radioTxPower=8, radioChannel=25, joinMethod=<EmberJoinMethod.USE_MAC_ASSOCIATION: 0>, nwkManagerId=0x0000, nwkUpdateId=0, channels=<Channels.ALL_CHANNELS: 134215680>)

And in some HA discussion i saw that some users having the same parameter set to 20. I think that is related to the Zigbee firmware that i flashed from https://github.com/arendst/Tasmota/raw/development/tools/fw_SonoffZigbeeBridge_ezsp/ncp-uart-sw_6.7.8_115200.ota, is that correct?
I was wondering if there were any "new" firmware with higher Tx power or maybe some way to change it myself.

Is here the rigth place to ask? Or maybe the github of the firmware developement?

[syssi]

Let's discuss the question here too because it could be helpful to other users using the ESPHome approach.

I've checked the bellows.zigbee.application and it looks like the value is hardcoded at the initialization and passed to the device. Could you create an issue at the bellows repository and ask for a solution?

https://github.com/zigpy/bellows/blob/dev/bellows/zigbee/application.py#L230-L231

It looks like the CONF_NWK_CHANNEL can be set via the HA configuration already:

zha:
  zigpy_config:
    network:
      channel: 15             # What channel the radio should try to use.
      channels: [15, 20, 25]  # Channel mask

A similar solution for the TX power would be nice.

[alelucc]

I have opened a new issue here zigpy/bellows#446 (comment)

[Hedda]

Do not know for ezsp (bellows) but for znp (zigpy-znp) it uses firmware default unless set tx_power via ZHA YAML configuration:

https://github.com/zigpy/zigpy-znp/blob/dev/README.md#configuration

zha:
  zigpy_config:
    znp_config:
      # "auto" picks the largest value that keeps the device's transmit buffer from getting full
      max_concurrent_requests: auto

      # Only if your stick has a built-in power amplifier (i.e. CC1352P and CC2592)
      # If set, must be between:
      #  * CC1352/2652:  -22 and 19
      #  * CC253x:       -22 and 22
      tx_power:  

So if same command is available for ezsp in ZHA and in the bellow library then ZHA YAML configuration should be something like:

https://www.home-assistant.io/integrations/zha#configuration---yaml

zha:
  zigpy_config:
    ezsp_config:
      tx_power: 20

The default in firmware will probably be set to around +10 dBm or less than that FCC and CE certification regulation does not allow higher power unless they also hardcode firmware so cannot use top end of 802.15.4 channel band (i.e. Zigbee channel 24 to 26).

https://community.silabs.com/s/article/tips-for-fcc-certification-on-silicon-labs-2-4ghz-802-15-4-based-solutions?language=en_US

"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."

Silicon Labs EFR32MG21 hardware does, however, support up to 20 dBm TX power but user need to set it themself if not default:

https://www.silabs.com/wireless/zigbee/efr32mg21-series-2-socs

Note! Commerical firmware plays it safe as legally you can use up 20 dBm transmission output power as long as not using the top end of the 802.15.4 channel band, (i.e. Zigbee channel 26 and occasionally Zigbee channels 24 an 25 at very high output powers).