How are device types recognized in Bluetooth?

Question

This is just hypothetical, but if I wanted to turn my android smartphone into a Bluetooth (BT) keyboard and have it show up as a keyboard in my computer's BT menu, how would I go about doing so? The BT pairing menu on my computer recognizes my android phone (without any app) as a phone, so I'm suspecting it has to do with something really low level, but is there any way of changing the type of BT device that my phone shows up as? Is there a way to do this in Android Studio?

Answer 1

Every Bluetooth device has one thing called COD or Class of Device. It is a 24 bit binary number.

For example, consider this : 00001100 00000010 01011010

This is real COD data of a smart phone. As you can see Minor Device class says that given device is smart phone. For more info. on COD you can read : https://www.question-defense.com/2013/01/12/bluetooth-cod-bluetooth-class-of-deviceclass-of-service-explained

Such things are set when Bluetooth process is initialized on low-level. So, I guess you can't make your phone to show up as a keyboard.