Add low speed data transmission from drone to controller

[Yamboy1]

Feature request

Feature description

After adding a PR #53 for low speed data transmission from the controller to the drone, it would be nice to have low speed data transmission from the drone to the controller. This way we have have custom commands, and request response style communication without requiring an external wifi network like we have in the past.

Implementation considerations

Relevant documentation links:

• https://developer.dji.com/doc/payload-sdk-tutorial/en/function-set/basic-function/data-transmission.html
• https://github.com/dji-sdk/Payload-SDK/blob/db9d05ee2b3289b957522d49b919861d33020c74/samples/sample_c/module_sample/data_transmission/test_data_transmission.c#L177-L190

We've been thinking about this in the context of communication between an M350 RTK and DJI RC Plus, but it should in theory work in other configurations too.

Like #53, I think it would make sense, at least originally, for this to be designed as a text based communication, as this is what the MSDK example uses.

Are you willing to submit a pull request to implement this change?

Not currently as I will no longer be working at the research group where I was working on these drones once #53 is merged, and thus won't be able to test my work. But I do think this is an important feature down the line, and should be implemented by someone. Feel free to ask for more information or considerations though, I'm sure I've missed a couple of things.

[biancabnd]

Hi @Yamboy1, Thank you for your contributions! :confetti_ball: We will definitely look into the PR you have opened and consider the enhancement you are proposing.