Synchronized multichannel universal serial bus

Abstract

The invention provides a method and apparatus for providing a synchronized multichannel universal serial bus, the method in one aspect comprising supplementing the signal channels in the USB specification to provide synchronization information from an external source, and in another aspect comprising observing USB traffic and locking a local clock signal of a USB device to a periodic signal contained in USB data traffic, wherein the locking is in respect of phase and/or frequency.

1 - 35 . (canceled) 
     
     
         36 . A method of providing a synchronized multichannel universal serial bus (USB), comprising:
 providing a plurality of USB devices with USB signals from a universal serial bus and synchronization information from a source external to said universal serial bus;   passing said synchronization information to transducers of said plurality of USB devices;   synchronizing said transducers to each other using said synchronization information from said external source;   observing USB traffic at a plurality of points in a USB tree;   measuring a round trip time of each of a plurality of individual packets;   determining relative phases of individual USB devices in said USB tree from said respective round trip times; and   adjusting any phase offsets of said respective USB devices according to said determined relative phases;   wherein said synchronization information from said external source is adapted for use in synchronizing said transducers of said plurality of USB devices to each other;   
       and said synchronization information is passed to the transducers of said plurality of USB devices substantially simultaneously wherein substantially simultaneously is defined to be within a variation in time between said devices that is less than a specified quantity δt. 
     
     
         37 . A method as claimed in  claim 36 , wherein said synchronization information includes a trigger signal and a clock signal. 
     
     
         38 . A method as claimed in  claim 36 , comprising:
 observing USB traffic; and   locking a local clock signal of a USB device to a periodic signal contained in said USB data traffic;   wherein said locking is in respect of phase, of frequency, or of both phase and frequency.   
     
     
         39 . A method as claimed in  claim 36 , further comprising issuing all USB devices in a USB topology with a trigger signal. 
     
     
         40 . A method as claimed in  claim 39 , wherein said trigger signal synchronously initiates or ceases operations on said USB devices. 
     
     
         41 . A method as claimed in  claim 39 , further including producing said trigger signal by using a Start of Frame packet, to trigger a transducer at a given time. 
     
     
         42 . A method as claimed in  claim 39 , including executing said operation in phase with a local oscillator. 
     
     
         43 . A synchronized multichannel universal serial bus (USB), comprising:
 a universal serial bus;   an external source of synchronization information, said external source being external to said universal serial bus, said synchronization information provided by said external source being adapted to supplement the USB signals from said universal serial bus and to be passed to respective transducers of a plurality of USB devices; and   circuitry to observe USB traffic at a plurality of points in a USB tree and to measure a round trip time of each of a plurality of individual packets, to obtain relative phases of individual USB devices in said USB tree;   wherein said synchronized multichannel universal serial bus is adapted to pass said synchronization information to said transducers, and said synchronization information is adapted to be used in synchronizing said transducers of said plurality of USB devices to each other, and   wherein said synchronisation information is passed to the transducers of said plurality of USB devices substantially simultaneously, wherein substantially simultaneously is defined to be within a variation in time between said devices that is less than a specified quantity δt.   
     
     
         44 . A universal serial bus as claimed in  claim 43 , wherein said synchronization information includes a trigger signal and a clock signal. 
     
     
         45 . A universal serial bus as claimed in  claim 43 , wherein said synchronization information comprises a local clock signal of a USB device, and said universal serial bus comprises circuitry to observe USB traffic and to lock said local clock signal to a periodic signal contained in said USB data traffic. 
     
     
         46 . A universal serial bus as claimed in  claim 43 , wherein said synchronisation information comprises a local clock signal of a USB device, and said universal serial bus comprises circuitry to observe USB traffic and to lock said local clock signal to said periodic signal contained in said USB data traffic in phase, in frequency, or in both phase and frequency. 
     
     
         47 . A universal serial bus as claimed in  claim 45 , wherein said circuitry is configured to decode and lock to a periodic data structure. 
     
     
         48 . A universal serial bus as claimed in  claim 43 , wherein said circuitry is configured to measure the roundtrip time of an ACK packet associated with a particular transaction, wherein said roundtrip time is usable in controlling the relative phase of the respective local clocks of said USB devices such that said USB devices are synchronized. 
     
     
         49 . A universal serial bus as claimed in  claim 43 , comprising circuitry for issuing all devices in a USB topology with a trigger signal. 
     
     
         50 . A universal serial bus as claimed in  claim 43 , comprising circuitry and logic to supply synchronization signals to USB devices at frequencies that correspond to national standards. 
     
     
         51 . A universal serial bus as claimed in  claim 43 , comprising a USB back plane for providing to attachable devices any one or more of USB signals, power, sockets and synchronization information. 
     
     
         52 . A system for providing real-time operation of one or more USB devices at any USB expansion hub connection point within a USB tree, configured to perform the method of  claim 36 . 
     
     
         53 . A system as claimed in  claim 52 , further providing real-time automated control and data acquisition functions using the one or more USB devices. 
     
     
         54 . A system as claimed in  claim 52 , further providing synchronous operation of the USB devices.