Lilygo T3S3 with LR1121 - incorrect default TX power setting?

[vladm]

Hi -

I have Lilygo T3S3 with LR1121 radio and when flashed initially it shows 30db as max transmit power, even though chip only supports 22db max. Is that a mistake?

Though interesting observation - when I set TX power to 22db, traces showing that remote nodes get lower signal from me.

p.s. Same board with sx1262 radio also shows 30DB max TX power by default, while chip only goes 22db max

[b8b8]

Thats the difference between the apps and the firmware.
The apps try and set it up to the legal limit of 30, while firmware per board are hardcoded to a max of 22 (what the hardware can handle).
It just doesnt display the end result in the app. It did at one point, but there was a regression.

The serial log should show the actual transmission power is still 22.

[vladm]

But when I query board using meshtastic console command, it also shows it's set
"txPower": 30

[b8b8]

what does it say at boot on the serial log?

[vladm]

i tried setting to 22 and 30, generates same serial output for LR1121

WARN  | ??:??:?? 5 LR11x0Interface(cs=7, irq=36, rst=8, busy=34)
DEBUG | ??:??:?? 5 LR11X0_DIO3_TCXO_VOLTAGE defined, using DIO3 as TCXO reference voltage at 3.000000 V
INFO  | ??:??:?? 5 Start meshradio init
INFO  | ??:??:?? 5 Radio freq=906.875, config.lora.frequency_offset=0.000
INFO  | ??:??:?? 5 Set radio: region=US, name=LongFast, config=0, ch=19, power=30
INFO  | ??:??:?? 5 myRegion->freqStart -> myRegion->freqEnd: 902.000000 -> 928.000000 (26.000000 MHz)
INFO  | ??:??:?? 5 numChannels: 104 x 250.000kHz
INFO  | ??:??:?? 5 channel_num: 20
INFO  | ??:??:?? 5 frequency: 906.875000
INFO  | ??:??:?? 5 Slot time: 28 msec
INFO  | ??:??:?? 5 Final Tx power: 22 dBm
INFO  | ??:??:?? 6 LR11x0 init result 0
DEBUG | ??:??:?? 6 LR11x0 Device 3, HW 34, FW 1.1, WiFi 0.0, GNSS 0.0
INFO  | ??:??:?? 6 Frequency set to 906.875000
INFO  | ??:??:?? 6 Bandwidth set to 250.000000
INFO  | ??:??:?? 6 Power output set to 22
DEBUG | ??:??:?? 6 Set DIO RF switch
INFO  | ??:??:?? 6 Set RX gain to boosted mode; result: 0
INFO  | ??:??:?? 6 LR1121 init success

[b8b8]

Looks to be working as expected.
Set to 22 as the board does not support 30 the firmware caps at 22.

I already mentioned that even though it is set for 30, there are guards in place that cap it at the max the board can do (it's UP TO 30). So while the setting is set to 30, it goes to 22. One is a LoRa config setting (30) regardless of hardware, one is the hardware limit (22) that cannot be overridden.

Your console query returns the power requested, not the power set after the guard is activated.

If you set 21 it would say ok 21.
If you set 22 it would says ok 22.
If you set 23 it would say "power output set to 22".