SBUS problem on custom autopilot hardware

Hello, I have designed my own autopilot hardware that is compatible with standard and related to this pinout table.

While testing my new PCB I have found that the SBUS input does not work at all. So I need some help to find out where the problem is. Please help?

Here is part of the RC input schematic:

74LVC2G86DCUR chip inverse input signal when PD15 in HIGH, as its written in comment in table
Anyway, I have connected PD15 line directly to 3.3 voltage to be sure that its inverts signal.

I also checked the signals with an osciloscope:


Here is what rc_input status shows:

nsh> rc_input status
INFO  [rc_input] Max update rate: 250 Hz
INFO  [rc_input] UART device: /dev/ttyS5
INFO  [rc_input] UART RX bytes: 224
INFO  [rc_input] RC state: searching for signal: SBUS
rc_input: cycle time: 28296 events, 179078us elapsed, 6.33us avg, min 4us max 1099us 17.836us rms
rc_input: publish interval: 0 events, 0.00us avg, min 0us max 0us 0.000us rms

And another one test, i have connect rc receiver to TELEM2 and switch RC_PORT_CONFIG to TELEM2 and it works fine. So I am shure that rc signal is received, it can be decoded. Also I have invert signal as its should be.

At the moment I have no idea what to check or change to fix it. Please help.

1 Like

Are you trying to connect it to USART6 Rx? Try with a Tx pin.

Yes its connected to, PC7 - USART6 RX.

Heh, in my case this pin is just not routed, I will try in next revision.

But why do you suggest this? Because USART will use the Tx pin if it set up as single wire?

Exactly, v6x has hardcoded singlewire in board_config.h. You can remove it and rebuild the firmware if you want to use it on the Rx pin.


Yes, everything works! Thank you! Just removed this line

Just keep in mind that when singlewire is not used telemetry is not possible.