TP-LINK TD-8817 v3.x

The TP-LINK logo, "MODEL:ADSL2+ (TC) A", "REV: 2.1", and a date code of 0937 is silkscreened on the board of a v3.20 unit;.

Per the serial logs below, this device would appear to be using ZyNOS.

Pinout
The pinout would appear to be the following... (3.3) (GND) (RxD) [TxD] J2

v
 * to USB port
 * to USB port