How to Add Functionality to Arm the Drone Without a Transmitter?

[shivam-daksh]

I am exploring ways to add functionality to arm the drone without using a transmitter. I'd appreciate guidance on which files and logic I should focus on. Specifically, I came across the tryArm function in the src/main/fc/fc_core.c file and wonder if this is the right place to start.

If anyone has experience or insights on implementing this kind of feature, please share your thoughts. Any references to related files, existing logic, or best practices would be highly valuable.

[sensei-hacker]

If you're going to modify the code, you might want to look at line # 222 of fc_core.c, in updateArmingStatus.

However, I would encourage you to consider connecting a little $2 microcontroller to a uart and have it set the arm channel whenever the conditions are met for arming. That is, your chip would take the role of the receiver, setting the arm channel high whenever it's appropriate to do so.

If it were me, I would probably reach for something like a Picaxe-08M2, which can do the job using just the 8-pin DIP; no circuit board needed.

Alternatively, there are MCUs that are mounted to a USB plug, so it's pretty much the size and weight of the plug. That will let you control when the motors spin up, when it's safe, and not require altering the INAV code and then hoping things don't go wrong when it goes into failsafe or something.