Huion Pentech 4.0

This is a new digital pen technology from Huion. It's similar to the WACOM Intuos digital datalink technology: a microcontroller-based pen that sends digital data to the tablet.

The design is very similar to the WACOM Graphire/Bamboo series, where the pen has an ASIC inside, and the tablet runs on a discrete diode-detector-based analog front end. The ASIC has markings of "CIREL CSAA1100V10" on it, indicating that it's a custom chip designed by the fabless design house Cirel Systems.

Further RE efforts are needed to understand the protocol and the IC inside the pen.