Smart audio switch and Logic setting

Matek_F405wing, rushtank+VTX. I tried to get 3 shift of power set with 25mw,200mw, assign one switch from 200mw to 800mw and together with arming activate to 200mw. here is my setting. it is not working.

one more setting I don’t if it is possible. how can I get power set with home distance increasing. like 1km with 25mw, 2km with 200mw, over 3km with max power.



AFAIK that only works in the latest github master version. Are you using that?

What is afaik? What do you mean by Master version?

AFAIK - as far as I know
github master - the latest version compiled directly from the github master branch source code, or downloaded from

The firmware that I’m using is the latest version. issued on 18th/june,2021

Do you get any indication in the GCS that it has recognized the VTX?

do you mean it should show the type of the VTX. like rushtank +?
I only see VTX 5800MHZ on the radio screen. but I did not notice any on the laptop.

Can you post your params and the output you get on the laptop

yes I can do that. thank you

RCx_option 94

something I dont understand that the VTX setting did not show at the param file saved but it show on the mission planner.
F405wing_NO7_202006023.param (24.8 KB)

Your config looks right - is the smart audio pin on your VTX connected to the TX pin of the UART (must be TX)?

@andyp1per Yes, it is on the tx pin of the uart. It is partially working As I can adjust the power from 200mw to 800mw. Plus the same set up used to work on Inav with the full functional of smart audio.

Can you change the frequency? What isn’t working?

@andyp1per Yes, I can change the frequency. but the power adjust is not fully working. I set the vtx_option to pit or 25mw It never works. The power is always start from 200mw

This is likely to be down to the implementation of your VTX and differences with TBS kit. The power settings are fairly approximate right now - at some point I plan to implement the proper SA 2.1 power levels, but that was too much work to include in 4.1

I’ve a similar setup (F405-WSE + Rush Tank Ultimate) running the latest Dev build 4.2, I’ve SA on the TX or SERIAL5 and SERIAL5_OPTIONS set to 68, so half duplex and TX_pulldown.
VTX_OPTIONS I’ve set at 19, so add leading zero (that’s stated in the TBS SA Spec) Pitmode ticked and also Pitmode until armed.
Channels/Bands seems a bit skewed - I normally fly on 5880 and to get that I have VTX_BAND = 3 and VTX_Channel = 7, VTX_FEQ show 5880. This is possibly confusing people as channels run 1>8 so 0>7 is possibly throwing them, been flying 6+ years and Fatshark 8 is 5880 all the time.
The above works as intended for me, I have the power on the OSD and when I power up it shows 0mw, when I arm it changes to 800mw as desired. I’m not sure pitmode is the best option here, with a plane a few feet from me waiting for sats to look I can just about see the OSD, a low power 25mW option may be a better way to go, no TX should heat up much at 25mW.

We’ve discussed the channel numbering a few times as others have been confused. It’s probably too late to change it for 4.1. That said you do get the correct information logged and visible in the OSD.

I have some of the AKK brand VTX’s that are also Smart Audio enabled so I’ll try these settings on those as well. For me this is just a documentation fix/clearer explanation, I’ve wrote out the above as an example hopefully it helps. As mentioned I’d consider a low power option, I was out flying this evening and only with a directional antenna pointed at the craft could I read the OSD, I would expect craft on bungee launchers etc to be further away so Pit Mode only prior to arm won’t be of much use.

Reading all this I’m a bit confused as to what serial option, protocol and baud rate to use for smart audio. what are the correct serial settings to use with matek F405-wing and RushFVP tank solo VTX ?

As long as you have it wired correctly the only thing you should need to set is SERIALx_PROTOCOL=37, everything else should be set by the firmware

I could get it to work but only the power level can be adjusted via a RC channel on the OSD. Is that how it supposed to work ?

There is no smart audio menu on OSD like in Inav .

I set a 3 pos switch on the RC channel to toggle the power level but I can only toggle 2 power levels instead of 4 that the VTX has, even those two power levels need some toggling of the switch to work and not very repeatable.