Hi everyone,

I am building a quadcopter (first one I am building on my own, second one I own in total) and more or less it is already working, it flies I have video etc., but the quad ... twitches every now an then which feels very bad. 
Video of the issue: https://drive.google.com/file/d/1M0R9QrW...sp=sharing

The FC I am using is a flywoo GOKU HDF4 EVO + dji air unit + 1106 motors. The fc uses blheli s but I flashed a dshot enabled firmware. The frame is from a transtec beetle which I was gifted by a friend (also the reason I got those motors). 

I believe I have already identified the issue to a certain degree.
As far as I can tell the FC needs softserial to transmit the osd to the googles (because the setup sheet says softserial tx B04 / rx B00) and I guess softserial sometimes takes too long and stalls the entire fc and then it overcompensates which causes the twitching.
Because if I disable soft serial and not go without the osd the twitching is gone.
I already lowered pid loop from 4k to 2k but it didn't change anything concerning the twitching.

However without the OSD I can not tell how much battery I have used and that seems fatal to me as well. 

So my question is can I
a) somehow get rid of this twitching by changing some settings in BF for the osd or the soft serial output or
b) can I somehow not use softserial with this fc, because my other drone does not need it or
c) can I somehow output battery voltage any other way to the goggles?

thanks for your help

Looking at the diagram there are 2 full Uarts on that FC.

What are you using Uart 2 (TX2/RX2) for?

You could skip the softserial connections in tgat connector and solder straight to Uart 2.

(22-Apr-2022, 03:06 PM)kafie1980 Wrote: Looking at the diagram there are 2 full Uarts on that FC.

What are you using Uart 2 (TX2/RX2) for?

You could skip the softserial connections in tgat connector and solder straight to Uart 2.

I thought the fc would be plug and play for the air unit and just used the cable of the FC to plug it into the connector but you are completely right. I am not using uart2 at all and I didn't plan to do it either so yes that is absolutely the right idea

I just have to solder the tx wire of the air unit to the tx uart 2 pad and same for rx and then enable it in the ports tab right?

you need to wire the tx to rx and rx to tx

As Hug’s explained:

FC RX —> DJI TX
FC TX —> DJI RX

Sorry for taking so long but I didn't get around to do the soldering until now (and bought a longer 8 pin jst cable to use). 

Of course I wired tx/rx fc to air unit the wrong way at first although I was very sure when I first did it, wrote the post asking for more help and when comparing the photo to the diagram which I had drawn for it I realized it wasn't the correct way around. 

Now it works, OSD via UART, softserial is completely disabled and hopefully no weird twitchy flying anymore.
I am gonna test it tomorrow, thanks a a lot already. 

I'll post the photos and the diagram anyway because why not show my terriable craftsmanship on this    
(This particular fc board is really not great, the supposed 9V output does not output 9V, thats why I have an additional BEC on there and I soldered the SBUS cable straight to the backside of the plug connector because apparently I could not verify that it has contact with any of the soldering pads on the bottom)

No dramas. Keep us posted on how the flight goes.

You could have soldered the DJI HDL wire to the SBUS pad next to motor 4 pads (top left section of the AIO board image you have attached and highlighted in red):

dont miss that there is a 9v regulator onboard, no external bec is needed for powering the airunit