How to make Android work as a USB HID device?

Question

Android

Hello.
I have a difficult task ahead of me: get the Android device to be recognized in the system as a HID device and send keystrokes.
All this is done for educational purposes (term paper), so I do not pursue any harmful goals.
For the fourth day I have been trying to find at least some information on this topic, but in vain. There are several contenders:
1) HID API . They have a mention of Android, but no more.
2) Here is this repository. Already closer, but it seems, too, not the same.
3) USB Host documentation directly from Googlers.
I feel like I'm walking around the problem, but not exactly. Maybe some of you have experience writing similar programs. If yes, please respond, I will be glad of any help.

Answer 1

Link 2 is what you need.