Smart audio on Rush Tank Ultimate Plus

I have smart audio working nicely on an Eachine TX805 but had some problems with the vtx itself and did buy Rush Ultimate Plus as a replacement.

The Rush unit seems to works OK (not yet tested in flight) except for the smart audio function (only working function is to switch pit mode on/off at all power levels set by button. Settings used are same as for the TX805 but alternatives have also been tested with no luck).

I have read the various earlier posts about the Rush units and smart audio (should have found them before buying though, my mistake) and obviously problems are related to the implementation made by Rush.

My question then is if anybody has found a fix for this or know of any work in progress to get smart audio working on these units?

I am the developer of SmartAudio on ArduPilot, I have a Rush Tank VTX and I cannot make it work - the SA implementation just seems broken. If it works on betaflight then its possible a Saleae trace would help me figure out what the problem is. All of the various broken implementations are captured in VTX_OPTIONS - its with trying to set some of those.

Thanks for the answer Andy.

I have earlier tried the various options without any luck but today I took the time to do it again.

For some reason I can get it working now. The crucial “vtx_option” seems to be ticking the setting “Add leading zero byte to requests”. Other alternatives make no difference but unticking the one above make it fail again.

I have tested it on two units and both are working, hope it stays that way.

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If you felt like making a wiki update to reflect this that would be great. We really need to start listing VTX’s and the options required for getting them working.

FYI @hwurzburg

@andyp1per happy to add, if we can somehow compile a list…I dont have the units or knowledge