I’m guessing you tried this:
Thanks, Allister. Actually, there are a few other parms I should try per the Spektrum SRXL2 wiki. I’ll try tomorrow…
SRXL2 receivers must be connected to a UART. SRXL2 receivers support a wide range of voltages, including the 5v available on a UART so connect GND to GND, VCC to VCC and the signal wire to the TX pin of the UART.
In the configuration of the serial port select the RCIN protocol and set the serial options to half-duplex operation. So for example for serial port 4:
Set :ref:SERIAL4_PROTOCOL <SERIAL4_PROTOCOL> = 23
Set :ref:SERIAL4_OPTIONS <SERIAL4_OPTIONS> = 4
Set :ref:RSSI_TYPE <RSSI_TYPE> = 3
Many single board flight controllers support RC input on serial port 6 only exposing the RX connection. For F7 flight controllers, such as the Kakute F7, it is necessary to swap the RX and TX pins in order to support SRXL2. It is also necessary to support serial access on the UART by using the board’s alternate configuration:
Set :ref:SERIAL6_PROTOCOL <SERIAL6_PROTOCOL> = 23
Set :ref:SERIAL6_OPTIONS <SERIAL6_OPTIONS> = 12
Set :ref:RSSI_TYPE <RSSI_TYPE> = 3
Set :ref:BRD_ALT_CONFIG <BRD_ALT_CONFIG> = 1
With the receiver connected and configured correctly proceed with RC calibration as normal.
Hi guys. So I reconfigured EXACTLY as suggested above…
SERIAL6_PROTOCOL = 23
SERIAL6_OPTIONS = 12
RSSI_TYPE = 3
BRD_ALT_CONFIG = 1
I have the data wire on FC UART Tx6. I rebooted MP, my DX6 radio, and my H743/SPM4650 receiver combo. No luck. I also tried ‘BRD_ALT_CONFIG = 0’ (in case I didn’t need that), and I also tried ‘SERIAL6_PROTOCAL’ = 4’ (as suggested in the upper section above). Still no green bars. However, I noticed that when I go into ‘Setup>Radio Calibration’, I can ever-so-briefly see the green bars, but they quickly disappear. What next???
Hi guys. I decided to download the latest ArduPilot Copter-Matek743 firmware, 4.0.7. I used BetaFlight so I could be sure to erase all previous data on the FC (I thought it may help to start from scratch). As such, I also reconfigured the parms once again…
SERIAL6_PROTOCOL = 23
SERIAL6_OPTIONS = 12
RSSI_TYPE = 3
BRD_ALT_CONFIG = 1
No Luck. I still do not have any green bars on the Radio calibration screen. At this point, I’m dead in the water unless someone has any suggestions. Thanks for all the help thus far.
Best Regards,
Dennis
Hi,
Just a hint. I use Multiplex RC with srxl to a pixhawk 2.4.8 Clone. To get it running, i connected the signal wire to the DSM port and i powered the rx via the ppm port to get 5v.
Regards,
Maarten
Thanks Maarten and Allister, I appreciate you taking the time to help me.
I’m not using a Pixhawk, Maarten, but I believe I’m using the suggested “DSM” port on my Matek H743 (Uart6, Rx6/Tx6), so I think I’m OK there.
As for the serial port, Allister, good call!!! I forgot that the ArduCopter doc said that Uart6 = Serial7, and I had hoped that you hit on the solution, but still no luck after changing the parms to SERIAL7 (still no green bars)! I also systematically tried a number of alternate combinations (8 connected to the Tx6 pin, 8 to the Rx6 pin) just in case, but no success…
SERIAL7_PROTOCOL = 23
SERIAL7_OPTIONS = 12 (half duplex, swap Rx and Tx), also tried 4 (half duplex)
RSSI_TYPE = 3 (Rc protocol), also tried 5 (telemetry radio)
BRD_ALT_CONFIG = 1 (alt board config), also tried 0 (default config)
I’ll continue to read everything I can to resolve this, but as I said, I’m an ArduPilot newbie, so thankful for any suggestions.
Best Regards,
Dennis
Long shot: Make sure you’ve set SERIAL6_PROTOCOL = -1. And any other port you may have tried but aren’t using. Sometimes if there’s multiples things get confusing.
Hi Allister. Good thought, and thanks, but I did remember to change the SERIAL6 parms back to defaults before I started testing the SERIAL7 mods. I’ll continue reading and looking for a solution. If I find something, I’ll be sure to update this thread.
Best Regards,
Dennis
Hi Guys.
This is still unresolved. I’ve tried everything I could think of, and tried all of the suggestions above, but still no luck. I cannot calibrate my radio in Mission Planner because I do not see the green bars on the screen. I’ll start a new thread with a different approach, requesting help with my SPECIFIC hardware. Perhaps someone has been down this road before. Thanks to all who have contributed. I appreciate the help!!!
Best Regards,
Dennis
@blakvette, exact same issue with Matek F765. Have you solved it yet?
I have tried Serial7 as well, nothing
Hi @RizHass:
Nope, I’m grounded. I removed a perfectly good RaceFlight FC and non-telemetry Spektrum RX from my quad (which flew great!), and installed the Matek H743-Slim, Matek GPS/Compass, and telemetry Spektrum SPM4650 in the hope that I could take advantage of the various ArduCopter flight modes and especially ‘Simple’ and ‘Super Simple’. I’m 73 and nearly blind now, so I need a better way to fly or I’m done. I was hoping that one of the devs would read my posts and get my combination working, but nothing so far. I haven’t tried lately… WAY too many other priorities, but if I ever get this thing to work, I’ll be sure to post the EXACT solution. Also, I had hoped the upcoming INAV release would support the H743, but I don’t think it will, so no help there either.
I’m trying the same thing on a Matek f405-std. no luck so far. Is there something special about Rx6? I’ve been trying on rx2 which will run the Rx as a regulAr non telemetry Rx, but not as srxl.
The dev team on another post says that 4.10 (waiting since last year) should support new Spectrum protocol.
I tried flashing my FC with 4.1 beta release but it won’t let me me load new fw. I must be doing something wrong.
If I ever make it to 70s, I’ll be building free flight. Full circle 
Download the .apj file from here and use the “Load custom Firmware” button in Mission Planner.
https://firmware.ardupilot.org/Copter/beta/MatekF765-Wing/
Or try the latest Dev version here:
https://firmware.ardupilot.org/Copter/latest/MatekF765-Wing/
Wow… reading this is like somebody followed me around for the last two weeks canonicalizing the story of my life… this is exactly what I have been going through with the h743-wing… i have been pulling my hair out and hey… I dont have that much hair left so before I start in on my beard will somebody PLEASE pull a rabbit out of their hat on this one??? So all this is to say … Misery loves company and I think im going to give INAV a try…
Hi Guys,
I had a similar problem with the same Board (Matek H743-Slim) but an SBUS Receiver (R-XSR).
For me the problem was solved by either specifying the baud rate (SERIAL7_BAUD) or the used receiver protocol (RC_PROTOCOLS).
In my case it either works with
RC_PROTOCOLS = 8 (This means SBUS. Note that this is a bitmask: 3 → 2^3 = 8)
or with
SERIAL7_BAUD = 111 (More information about the protocols: RC Input and Output — Dev documentation)
I think it should be prefered to change RC_PROTOCOLS and not to touch SERIAL7_BAUD.
Of course you would have to specify the DSM protocol (32) or whatever protocol you use (there are also DSMX, SRXL2, … Spektrum RC Systems — Copter documentation).
I hope that helps!
Hi Guys:
!!!SUCCESS!!!
Had to step away from this for awhile… WAY too many priorities. For the last few days, I’ve re-read everything I could find about connecting my Spektrum SPM4650 (DSMX/SRXL2) receiver to my Matek H743-Slim autopilot. I applied everything I’ve learned, and was finally able to see the ‘Radio Calibration’ green bars for my Spektrum DX6 Radio!
Many thanks to all of you who have offered valuable suggestions. Without you, I’d be nowhere. 
To accomplish this, I decided to start from scratch. I can’t stress enough… reboot Mission Planner, Rx, Tx, FC, and GPS/compass often! If you make ANY changes, reboot or you may get false results! Here’s what worked for me…
- Connected the SINGLE SRXL2 signal wire from my Rx to the Tx6 (Serial7) pad. For telemetry to work, must use the Tx pad.
- Installed latest Spektrum v2.44 SPM4650 Rx firmware.
- Installed latest Spektrum v2.08 DX6 Tx firmware.
- Installed latest v1.3.75 Mission Planner.
- Installed latest STM32 Cube Programmer (used to flash my H743 autopilot with Arducopter/Matek H743 firmware).
- Using STM32 Cube Programmer, I did a full ‘Chip Erase’, then Flashed latest v4.1.1 Arducopter/Matek H743 firmware.
- MP > Setup tab > Mandatory Hardware > Frame Type (‘X’ for my Diatone Tyrant).
- MP > Setup tab > Mandatory Hardware > Accel Calibration (worked fine).
- MP > Setup Tab > Mandatory Hardware > Compass (if this never completes, first hit the ‘Large Vehicle MagCal’ button, point your copter south, enter ‘180’, then run the calibration again).
- MP > Config tab > Full Parameter LIST > BRD_ALT = 0 (no need to use ‘1’ unless you MUST use the Rx6 pad on the FC).
- MP > Config tab > Full Parameter LIST > RC_PROTOCOLS = 257 (specifies that the Rx is using SRXL2 to speak to the FC).
- MP > Config tab > Full Parameter LIST > RSSI_TYPE = 3 (specifies that this is a receiver).
- MP > Config tab > Full Parameter LIST > SERIAL7_BAUD = 115 (115,000 baud).
- MP > Config tab > Full Parameter LIST > SERIAL7_PROTOCOL = 23 (Rx input).
- MP > Config tab > Full Parameter LIST > SERIAL7_OPTIONS = 4 (half duplex on single signal wire).
- MP > Config tab > Full Parameter LIST > ***** WRITE PARAMS button, upper right *****
- REBOOT EVERYTHING, power on TX, Rx, FC, GPS/compass, and CONFIRM Rx/Tx BIND (my SPM4650 Rx has a solid red LED)
- MP > Setup Tab > Mandatory Hardware > Radio Calibration > !!!SUCCESS!!! (green bars show on screen!).
Hopefully, this will help any of you with the same or similar hardware.
Best Regards,
Dennis
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That’s awesome! Glad to hear you got it working.
Thanks Allister… couldn’t have done it without your guidance!!! 
Best Regards,
Dennis
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