APPARATUS AND METHODS FOR TIMESTAMPING IN A SYSTEM SYNCHRONIZING CONTROLLER AND SENSORS

摘要

Disclosed are methods and apparatus for synchronizing a controller and sensors in a system. A timestamp is provided in a host controller of an interface event on an interface coupled with host controller through detecting a message from a sensor on the interface that identifies the issuance of the interface event caused by the sensor at a first time. In response, the controller issues first and second events on the interface at respective second and third times, while concurrently counting cycles of a clock in the controller after each issuance. The controller also receives a first and second sensor counts representing the internal sensor clock times noted for the first and second events. The controller may then accurately calculate the timestamp of the interface event corresponding to the first time based on both internal controller counts and the sensor counts without needing a timestamp from the sensor directly.

主权项

1. A method for providing a timestamp in a host controller of an interface event on an interface coupled with host controller, the method comprising:
detecting a message from a sensor on the interface that identifies the issuance of the interface event caused by the sensor, the interface event occurring at a first time on the sensor; issuing a first event on the interface at a second time after the first time in the response to the received message and starting a first count of cycles of a host controller clock, the start of the first count being concurrent with issuing the first event; issuing a second event on the interface at third time after the second time; receiving a first sensor clock count and a second sensor clock count from the sensor, where the first sensor clock count is a count of cycles of an internal sensor clock from the first time to the second time and the second sensor clock count is a count of cycles of the internal sensor clock from the second time to the third time; and determining within the host controller the timestamp of the interface event corresponding to the first time based at least in part on the first count of cycles of a host controller clock, the first sensor clock count, the second sensor clock count, and a host controller timestamp of the second time.