Block, Inc.
Monitoring and recovery for a USB interface

Abstract:

A first device and a second device enter a USB monitoring mode. The second device transmits monitoring messages on a periodic basis, while the first device has a monitoring timer that it resets each time a monitoring message is received. If a monitoring message is not received before the monitoring timer expires, the first device starts a reconnect timer. After a certain number of failed attempts to receive monitoring messages, the first device takes corrective action to restore USB communications.