The device is based on the HL-340 chip. The RS485 side is handled by MAX485ESA+. The bus resistor (R7) is unpopulated but the footprint is available if needed. The A(-) contact is on the left side of the green connector when viewed from the front. Remember to connect A - A and B - B.

Below are some log outputs produced by the Linux 3.13 kernel:

ID 1a86:7523 QinHeng Electronics HL-340 USB-Serial adapter usbserial: USB Serial support registered for ch341-uart