Futaba R7008SB not working on Kakute F4 V2 mini

Hello everyone !

So I got a LDARC Flyball 230, and I would like to use a Kakute F4 V2 mini stack on it with a Futaba R7008SB receiver. It’s a S-BUS receiver, and I soldered it on the R3 pin of the Kakute. I know it should work, because when I flash the Kakute with a betaflight firmware, it works just fine. But with ArduCopter, on the Radio Calibration screen, nothing reacts to any of my inputs and stay at 0.
That’s why I think I need to change a parameter, but I don’t know which one.

Does anyone know how to fix that ?
Thanks !

My current set of parameters : flyball_no_receiver.param (17.8 KB)

The hwdef setup for the KakuteF4 Mini only supports serial input for RC. So I think for SBUS you may have to set the option on SERIAL3 to invert the RX since SBUS is an inverted protocol.

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Thanks for the quick answer !
I just tried, but it doesn’t seems to work either.

Some quick questions though :
-Are you sure R3 pin correspond to Serial 3 ? I know it’s not the case for the Kakute F4 (see here). So maybe I should try this with another Serial param.
-Also, I think the pin should be inverted automatically, unless Ardupilot disables it (see Kakute f4v2 mini docs here, page 7).
-Finally, to set up which pin should be used to receive RC data, I should set its protocol to 23 right ?

Thanks again !

Yeah, sorry F4 does not support inversion in software. I’m trying to find out how the SBUS inversion works - there is a pin that controls this but I can’t see how it is used.

R3 definitely corresponds to SERIAL3, I changed the UART order to match the docs.

Yes protocol 23

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Ok I think this isn’t implemented. If I get a chance I’ll try to fix it this week.

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Thank you very much !
Let me know if you manage to do it :smile:

I can’t test, but can you see if this helps at all?

arducopter.zip (615.5 KB)

No it’s still like nothing is received.
Do I have to change a parameter compared to what i had previously ?
I have serial3_protocol = 23, serial3_baud = 115 and serial3_option = 1.

Tridge suggested a different way. Try this one:

arducopter (2).zip (615.5 KB)

only SERIAL3_PROTOCOL should matter, but you could try setting SERIAL3_OPTIONS = 1 as well

No still not :confused:
I tried to reboot and set SERIAL3_OPTIONS to 0, but still nothing

Sorry, was a bug in my changes - try this one

arducopter.zip (615.4 KB)

No, same results as before.
You’re trying to invert the R3 pin to be compatible with S-BUS protocol in the firmware right ?

Yeah there is a pin you can pull so that the hardware inversion kicks in. We appear to have support for that - one last thing to try is if it is active high

So you want me to see if the R3 pin is in a high state ? But since it’s a signal pin, how should I do that ?
With a multimeter, i read 340mV approximately.

Here is a build with active high for the pin, see if it makes any difference. You should continue to set SERIAL3_OPTIONS = 1.

arducopter.zip (615.5 KB)

With this build, when my radio is turned on, I read 350mV between R3 and a ground pin.

Also when I tilt the throttle stick, it changes the voltage read.

But only when the radio is on? Weird. I am out of ideas for now. I think this is the right approach, but will require deeper investigation. I have some TBS RX’s I can setup as SBUS I think so will need to try that.

When the radio is off (but the receiver is still there, i didn’t unsoldered it), i read 340mV.
With the receiver unsoldered, i read 3mV.

No problems, thank you for what you already did !