I'm trying to wire my crossfire nano with full functionality, with the CRSF protocol to an emax babyhawk r pro 4 that uses a mini magnum iii f405 flight controller.

The bottom of the board has UART1-5 pads, but I know that doesn't mean much. I'm still learning how to read the configurations from the dump and I'd appreciate some help to guide me down the right path. 

BetaFlight has UART1 and UART3 showing unused with UART2 looking configured for a receiver. I believe it's inverted due to the quad coming with a FrSky D8. 

1) Is it correct that I cannot use an inverted UART for the crossfire rx? 
a) Are software inversions of UART's possible on this board?

2) Are UART1 and UART3 open per the dump?
Unfortunately, it looks like they're in use to me, although I have no idea what these HEX(?) addresses are for lol

Dump:
https://pastebin.com/Kjw0vU4s

BF ports tab

Yes, UART2 on the Matek F405 boards is configured for SBUS which has a hardware inverter on the RX line. So you can't use that UART for a Crossfire receiver.

There are no software inverters on the Matek F405 flight controllers.

You can use any other spare UART. I have the Matek F405-STD and am running the Crossfire Nano RX on UART4.

The "Hex" numbers next to the resource mapping aren't hex numbers. They are MCU pin identifiers. When a resource is mapped to an MCU pin, the signal is output (or input) on that pin. The pinout for an F4 MCU is below.

(28-May-2020, 12:01 AM)SnowLeopardFPV Wrote: Yes, UART2 on the Matek F405 boards is configured for SBUS which has a hardware inverter on the RX line. So you can't use that UART for a Crossfire receiver.

There are no software inverters on the Matek F405 flight controllers.

You can use any other spare UART. I have the Matek F405-STD and am running the Crossfire Nano RX on UART4.

The "Hex" numbers next to the resource mapping aren't hex numbers. They are MCU pin identifiers. When a resource is mapped to an MCU pin, the signal is output (or input) on that pin. The pinout for an F4 MCU is below.

Great news, I was reading a lot of posts online saying there's nothing open on these boards so forgive me for still wanting to verify I get the right answer here. I believe they're for an earlier version of the board, though. I or II, or one with a F3 FC.

You said I can use any other spare UART. In this case, would that be UART1 and UART3? Is BF going to be 100% accurate on the ports tab or will there ever be background settings that don't show in the GUI that I need to learn to check? 

These look to be used, or incompatible:
UART2 - inverted
UART4 - listed as camera, does this mean I can change camera configurations via stick inputs? 
UART5 - Vtx Smart audio

Thanks for your help over the past few days. Trying to do as much research as possible before posting a thread.

I'm not sure what you mean when you say "nothing is open" on these boards. If you mean the hardware, then no, none of the hardware is open. It's proprietary and the IP of the manufacturer that designed it. Of course, some companies reverse engineer and copy/clone other manufacturers flight controller design. The EMAX Magnum fight controllers use a design copied (or at least based on) the Matek F405 boards, thus my reference to Matek boards in my previous post.

As to the spare UARTs, yes you can use UART1 or UART3.

As long as you haven't messed with the default serial receiver and telemetry inversion, or the half duplex settings for those in the CLI then Crossfire just works with those default settings no problem. You just need to switch on "Serial RX" for the UART and set the Serial Provider to "CRSF". That is all

(28-May-2020, 12:22 AM)SnowLeopardFPV Wrote: I'm not sure what you mean when you say "nothing is open" on these boards. If you mean the hardware, then no, none of the hardware is open. It's proprietary and the IP of the manufacturer that designed it. Of course, some companies reverse engineer and copy/clone other manufacturers flight controller design. The EMAX Magnum fight controllers use a design copied (or at least based on) the Matek F405 boards, thus my reference to Matek boards in my previous post.

As to the spare UARTs, yes you can use UART1 or UART3.

As long as you haven't messed with the default serial receiver and telemetry inversion, or the half duplex settings for those in the CLI then Crossfire just works with those default settings no problem. You just need to switch on "Serial RX" for the UART and set the Serial Provider to "CRSF". That is all

Whoops, let me clarify. No UART's open, all being used by peripherals. I only asked about "hidden" things on UART's because I think the Emax Buzz has the ability to turn the Vtx down/off and it doesn't show up anywhere but the dump so who knows if that's commonplace - doesn't seem to be. 

I'll disable serial on UART2, enable it on UART1, and solder the crossfire to UART1 

Fantastic, adding this to my book of knowledge and moving forward!

(28-May-2020, 12:22 AM)SnowLeopardFPV Wrote: I'm not sure what you mean when you say "nothing is open" on these boards. If you mean the hardware, then no, none of the hardware is open. It's proprietary and the IP of the manufacturer that designed it. Of course, some companies reverse engineer and copy/clone other manufacturers flight controller design. The EMAX Magnum fight controllers use a design copied (or at least based on) the Matek F405 boards, thus my reference to Matek boards in my previous post.

As to the spare UARTs, yes you can use UART1 or UART3.

As long as you haven't messed with the default serial receiver and telemetry inversion, or the half duplex settings for those in the CLI then Crossfire just works with those default settings no problem. You just need to switch on "Serial RX" for the UART and set the Serial Provider to "CRSF". That is all

I'm new in this FPV world, right now I'm flying with Emax Hawk Sport with Mini Magnum III F4 stack. I wanna upgrade it with R9MM receiver and GPS, is that possible? Since you mentioned the available UARTs are UART1 and UART3.

Thanks. 

(13-Jun-2020, 02:33 PM)afrireksa Wrote: I'm new in this FPV world, right now I'm flying with Emax Hawk Sport with Mini Magnum III F4 stack. I wanna upgrade it with R9MM receiver and GPS, is that possible? Since you mentioned the available UARTs are UART1 and UART2.

If you have 2 spare unused UARTs then that is all you need --> one for the R9MM (running FPORT firmware), and the other for GPS. So it sounds like you are all good

(13-Jun-2020, 03:56 PM)SnowLeopardFPV Wrote: If you have 2 spare unused UARTs then that is all you need --> one for the R9MM (running FPORT firmware), and the other for GPS. So it sounds like you are all good

Actually I'm not sure how many spare UARTs does Mini Magnum III F4 have, I just know it has 5 UARTs:

UART1 - I think it is related to DSMX receiver but it's unused since I'm using FrSky receiver
UART2 - inverted for SBUS
UART3 - I think this one also unused
UART4 - camera configuration
UART5 - VTX smart audio

So if I want to upgrade to R9MM receiver and GPS, I need to find unused TX and solder them?

so it looks like you have 5 full uart breakout pads. therefore, you can use any one of the uart for F.port. another one for GPS. and you still have three more, which you will use for VTX SA and camera config. with one uart still available.