Can I make a PR to add support to AllXF serial gimbal?

[yukihiratype2]

I've bought a AllXF C-20T gimbal, which is similar to Walksnail gimbal but have different data structure , I've add some code but not finished yet (typedef has been made), after I finished add support to AllXF's gimbal, would you ( INAV maintainers ) accept this kind of changes?
Here are my changes:
master...yukihiratype2:inav:yukihiratype2-allxf-serial-gimbal

[sensei-hacker]

In my opinion, it looks like it might be a reasonable addition. It's not too much code - won't take up very much flash. At a glance, the code seems reasonable.

If you make a PR, plan on some others may have a number of comments. Sometimes there is a lot of discussion about a change.

[yukihiratype2]

It's nice to hear that, ty

[glennvenghaus]

Do you have a link to this gimbal ? Is this not the XF robots C-20T ? If so this has been supported by INAV 8 since a while now and i am using 2 atm driven by inav via serial uart connection. Its also the same as the caddx gm3 model only differently branded.
There is a special alloy version by the same company , but that seems just a different material and not different code etc. So just to doublecheck you are not doing work that has already been done ;-)

[yukihiratype2]

Wait a minute, I'm exactly trying to support AllXF's C-20T, here is the link C-20T. And I double checked the INAV serial gimbal source code and C-20T's private UART protocol (in the Downloads tab of the product page), they are not the same:

• The Sync header is different. AllXF is 0xA9 0x5B, in INAV, the serial gimbal sync header is 0xA5, 0x5A.
• The data structure sent by host to gimbal is different.

I've tried to connect my C-20T gimbal to my Speedybee F405 Wing with UART4 port and it didn't working. I don't understand how could INAV use different serial protocol to control AllXF's C-20T gimbal, could you please kindly tell me your configuration 😳.

[glennvenghaus]

sure ! Not at home right now as flying with it as we speak near the beach but will check when home. But it nothing special i remembered. Just standard rx/tc cross connection , set that port to serial gimbal and specify in the configurator on one of the pages which channel you want mapped to pitch and which to roll. Also make sure you have updated the gimbal to the latest firmware for it to work as inav support in one of the latest versions and have the correct wires connected to your uart

[glennvenghaus]

Ok, just got home and i checked the config.

1. You need to be on at least firmware 3.4 where INAV support was added. So if not , upgrade the firmware and just put the latest 3.6 on. The gimbal normaly comes with a small cable that allows you to upgrade (and optionaly tune / calibrate etc ) the gimbal
   

2. Make sure you connect the rx/tx wires correctly. The image shows them top down
   
   (of course connect rx > tx and tx > rx )

3. On inav 8.1 or higher set the port on the uart where you connected the gimbal to "serial gimbal"
   

4. On the configuration tab , set the channels you want to control pitch and roll and optionaly set the gimbal sensitivity. (As of the recent inav's you can also program the sensitivty from the programming tab. I use it to control sensitivity in flight with a knob)

5. Optionally you can set gimbal modes in the modes tab. I dont use that and fly it only in fpv stabilisation mode with manual pan/tilt control via knows/yaw stick.

Thats it. I have 2 of them working on my planes.

[yukihiratype2]

Thank you kindly for your previous assistance. I've carefully implemented your suggestions and would like to share my progress:

1. The C-20T Release and Upgrade Records do confirm INAV serial gimbal control support from V3.4 onward. Using the official client, I've successfully upgraded my gimbal to V3.6.
2. I've configured use my Speedybee F405 Wing 's UART4 port as gimbal serial at 115200.
3. I've configured UART4 on my Speedybee F405 Wing for gimbal serial communication at 115200 baud. The wiring sequence (PowerIn -> GND -> Rx -> Tx, from top to bottom ) appears correct, with gimbal Rx connected to FC Tx and vice versa.
4. My logic analyzer confirms valid data transmission from UART4_TX, including the expected A5 5A sync header. Changing gimbal modes and tilt inputs via RC controller produces observable data variations (attached screenshots).

Below are screenshots:
Gimbal firmware confirmed at V3.6

Valid serial communication observed

Use different gimbal mode / changed tilt input use my RC controller changes reflected in output data:

Despite these configurations, the gimbal remains unresponsive (remains in the center position). Next step I'll use my ESP32 to write a small program to send private UART protocol as AllXF's document suggest,

[glennvenghaus]

I found the issue. To check some stuff for you in the gimbal config, i saw mine was running 3.4. So i upgraded to 3.6 and i lost gimbal control. I rolled back to 3.4 it worked again. So 3.6 broke INAV support !!!

Online i only found the 3.6 package so i have attached a version 3.4 i downloaded some time ago when i set it up. Will see if i can online inform the guys from XF robot as not sure if they know.

C-20_Upgrade_Package_V3.4.zip

[glennvenghaus]

I send a mail to support@allxianfei.com and informed them of the insue including a link to this post.

[yukihiratype2]

Thank you, it is working now. I'm very appreciate your assistance for this test and thanks for your precious time.
You are right, the V3.4 is working with inav without any problem. I bought this gimbal recently, so it has V3.6 as stock firmware and AllXF's website only provides V3.6 fm, so I never had a chance to test older fm, what a sad story.
So my theory now is: Before V3.6, the C-20T's UART protocol is same with GM3. After V3.6, C-20T is using their own private UART protocol as there official website suggest.
At least it is working without any problem (with older V3.4 fm), yahhhh.