help with 20x20 LDARC/KK F4 board and Sbus

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help with 20x20 LDARC/KK F4 board and Sbus

ehrans

i'm not able to make standard sbus from an r9mm works with this f4 omnibusf4sd board. Is not a problem with betaflight, cleanflight, inav, etc. serialrx on uart1, but i'm not able to use on dronin after flash.

rxport parameter have not sbus option, inverted sbus is only available at main port, but seems not to work. tried all thos uninverted sbus of the other ports. I think the problem is the sahred receiver port wich works with ppm or sbus at the same pin, i remember the airbot trick of desolder a resistance to make it work, but i have no clue what to do on this board
https://www.banggood.com/LDARCKingkong-20x20mm-2-Layer-KK-Flytower-20A-BLheli_S-ESC-Omnibus-F4-Flight-Controller-w-OSD-p-1243025.html?cur_warehouse=CN

since i no need any change to make it work correctly on betaflight or inav, why i should desolder something to use dronin? i suppose is not realy needed on this borad, is it?

i'll apreciate any hint, thanks in advance.

raemin

Not every UART do support PPM/SBUS so you just have to find the one that dRonin considers as such. I do not have the specific layout of this board, so you will have to venture into some trial and error...

ehrans

sorry. reflashed betaflight to confirm. is uart6 (obiusly with an inverter on than rx pin.) where the serialrx works

the thing is, not other populated rx signal on board. just the rx connector as you can see in the banggood photos.

wich will be the try sequence?

edit:

btw... wich is supposed to be the uart6? main port? flexy port? rxport usart? rx port? is a bit anoying not knwo wich port im touching

raemin

The firmware you are using is a generic firmware originally designed for the Revolution flight controller. So you have to read the Revolution Schematic (https://github.com/d-ronin/dronin-hw/blob/master/revolution/Revolution%20Schematic.pdf). From then on identify on this schematic the processor pin used for UART6, and back to your board, find the UART that is connected to the same processor pin. Based on the spreadsheet I would say:

UART6 Tx > processor pin n°37
UART6 Rx > processor pin n°38

Not 100% guaranteed to work as I am assuming that UART6 in dRonin is also UART6 in openPilot, but this probably correct given dRonin is an openpilot fork (so to say).