Multi-camera synchronization through receiver hub back channel

Abstract

A driver assistance system includes a first camera, a second camera, a first serial interface circuit, a second serial interface circuit, and a hub interface circuit. The first serial interface circuit is coupled to the first camera. The second serial interface circuit is coupled to the second camera. The hub interface circuit is coupled to the first serial interface circuit and the second serial interface circuit. The hub interface circuit is configured to receive transmissions from the first serial interface circuit and the second serial interface circuit, and to transmit control information to the first serial interface circuit and the second serial interface circuit. The hub interface is also configured to encode a clock signal in the control information.

What is claimed is: 
     
         1 . A driver assistance system, comprising:
 a first camera;   a first serial interface circuit coupled to the first camera;   a second camera;   a second serial interface circuit coupled to the second camera;   a hub interface circuit coupled to the first serial interface circuit and the second serial interface circuit;   wherein the hub interface circuit is configured to:
 receive transmissions from the first serial interface circuit and the second serial interface circuit; 
 transmit control information to the first serial interface circuit and the second serial interface circuit; and 
 encode a clock signal in the control information. 
   
     
     
         2 . The driver assistance system of  claim 1 , wherein the first serial interface circuit and the second serial interface circuit each comprise: a clock recovery circuit configured to extract the clock signal from the control information received from the hub interface circuit. 
     
     
         3 . The driver assistance system of  claim 2 , wherein the first serial interface circuit and the second serial interface circuit include clock generation circuitry configured to generate a clock based on the clock signal extracted from the control information. 
     
     
         4 . The driver assistance system of  claim 3 , wherein the first serial interface circuit and the second serial interface circuit include no crystal to control the clock. 
     
     
         5 . The driver assistance system of  claim 3 , wherein the first serial interface circuit and the second serial interface circuit are configured to provide the clock to the first camera and the second camera. 
     
     
         6 . The driver assistance system of  claim 1 , wherein the hub interface circuit is configured to encode a frame sync signal in the control information. 
     
     
         7 . The driver assistance system of  claim 6 , wherein the first serial interface circuit and the second serial interface circuit are configured to extract the frame sync signal from the control information. 
     
     
         8 . The driver assistance system of  claim 7 , wherein the first serial interface circuit and the second serial interface circuit are configured to provide the frame sync signal extracted from the control information to the first camera and the second camera. 
     
     
         9 . The driver assistance system of  claim 8 , wherein the first serial interface circuit and the second serial interface circuit are configured to transmit video data to the hub interface circuit, the video data comprising video frames synchronized to the frame sync signal extracted from the control information. 
     
     
         10 . The driver assistance system of  claim 1 , further comprising:
 a first coaxial cable disposed between the hub interface circuit and the first serial interface circuit; and   a second coaxial cable disposed between the hub interface circuit and the second serial interface circuit;   wherein the hub interface circuit is configured to transmit the control information to the first serial interface circuit via the first coaxial cable; and   wherein the hub interface circuit is configured to transmit the control information to the second serial interface circuit via the second coaxial cable.   
     
     
         11 . A video control system, comprising:
 a hub interface circuit comprising:
 a clock generator configured to synchronize a clock signal to a reference clock; and 
 a plurality of transceivers, each of the transceivers configured to:
 communicate bidirectionally with a serial interface circuit; and 
 
   encode the clock signal in control information to be transmitted to a serial interface circuit;   a plurality of serial interface circuits, each of the serial interface circuits configured to bidirectionally communicate with the hub interface circuit, each of the serial interface circuits comprising:
 a clock recovery circuit configured to extract the clock signal from the control information transmitted by the hub interface circuit; and 
 a camera interface configured to provide, to a camera, a synchronization signal generated from the clock signal extracted from the control information. 
   
     
     
         12 . The video control system of  claim 11 , wherein each of the serial interface circuits comprise clock generation circuitry configured to generate a clock based on the clock signal extracted from the control information. 
     
     
         13 . The video control system of  claim 12 , wherein the serial interface circuits comprise no crystal to control a frequency of the clock. 
     
     
         14 . The video control system of  claim 11 , wherein the hub interface circuit comprises frame sync generation circuitry configured to generate a frame sync signal; and wherein each of the transceivers is configured to encode the frame sync signal in the control information to be transmitted to a serial interface circuit. 
     
     
         15 . The video control system of  claim 14 , wherein each of the serial interface circuits comprises frame sync recovery circuitry configured to extract the frame sync signal from the control information. 
     
     
         16 . The video control system of  claim 15 , wherein each of the serial interface circuits is configured to provide the frame sync signal extracted from the control information to a camera. 
     
     
         17 . The video control system of  claim 15 , wherein each of the serial interface circuits is configured to transmit video data to the hub interface circuit, the video data comprising video frames synchronized to the frame sync signal extracted from the control information and wherein the video data is synchronized to the synchronization signal. 
     
     
         18 . The video control system of  claim 11 , wherein each of the serial interface circuits is configured to transmit video data to the hub interface circuit over a coaxial cable, and the hub interface circuit is configured to transmit the control information over the coaxial cable. 
     
     
         19 . A driver assistance system, comprising:
 a hub interface circuit comprising:
 a clock generator configured to synchronize a clock signal to a reference clock; 
 frame sync generation circuitry configured to generate a frame sync signal; 
 a plurality of transceivers, each of the transceivers configured to:
 communicate bidirectionally with a serial interface circuit; and 
 encode the clock signal and the frame sync signal in control information to be transmitted to a serial interface circuit; 
 
   a plurality of serial interface circuits, each of the serial interface circuits configured to bidirectionally communicate with the hub interface circuit, each of the serial interface circuits comprising:
 a clock recovery circuit configured to extract the clock signal from the control information transmitted by the hub interface circuit; 
 clock generation circuitry configured to generate a clock based on the clock signal extracted from the control information; 
 frame sync recovery circuitry configured to extract the frame sync signal from the control information; and 
 a camera interface configured to provide the clock and the frame sync signal to a camera; and 
   a plurality of cameras, each of the cameras coupled to one of the serial interface circuits.   
     
     
         20 . The driver assistance system of  claim 19 , wherein the serial interface circuits comprise no crystal to control a frequency of the clock.