OK, see my initial writeup at Github.com (https://opengeometry.github.io/NOTES/beagleboneblack/).

Using USB Gadget driver and BeagleBone Black, I was successful in making scriptable 

• keyboard
• mouse --- relative mouse
• touchscreen --- absolute mouse, basically simple one-finger touchscreen

I will try out Raspberry Pi and Odroid, after I do some yardwork that I've been neglecting.