Block, Inc.
Multi-mode USB interface

Abstract:

A merchant device has a USB interface that includes an ID pin and a voltage pin. When the merchant device receives an oscillating signal at the ID pin, it connects the voltage pin to a power supply of the merchant device. The merchant device also includes a download switch coupled to the ID pin. When it is desired to reprogram a device connected by the USB interface, the download switch provides a programming voltage to the ID pin.