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DS90UB954-Q1: TI913A + TI935 synchronization using an internally generated FrameSync on Des TI954

omar chakroun
Prodigy 225 points
Part Number: DS90UB954-Q1

Hi there,

i have a question related to the synchronization between two different types of serializers using the same framesync signal generated internally on the TI954.

is it possible to generate a framesync signal on the TI954 side and send it/share it with both TI913A and TI935 and get them both synchronized on a frame level or the synchronization signal will be altered/adapted depending on the BC frequency. if the framesync is altered, is there another way to do it to keep them synced?

thank you and best regards,

omar

  • 0
    TI__Guru** 103215 points

    Hello Omar,

    Frame sync can be shared between 935 and 913A. There will be small differences in the transmission delay between the signal reaching each sensor due to the different back channel speeds, but this difference is orders of magnitude smaller compared to the frame time. Frame time is typically on the order of 10s of milliseconds while delay difference in BC signal to the sensor is on the order of 10s of microseconds. 

    Best Regards,

    Casey 

  • 0 in reply to Casey McCrea
    Prodigy 225 points

    Hi Casey,

    thank you for the quick reply.

    I'm accounting for a design that needs a synchronization on the frame level with a maximum desynchronization of around 200 microseconds between all the cameras. am i able to respect this constraint while sharing the FrameSync using the BC. please find attached the design that i'm thinking of. one TI954 will be considered as master and it will generate the framesync to be forwarded on the BC for its own use but also shares it will another TI954 that is considered as a slave.

    thank you again,

    best regards,

    omar

  • 0 in reply to omar chakroun
    TI__Guru** 103215 points

    Hello Omar, 

    Yes, 200ms max de-synchronization should be easily achievable given the delays associated with these sync signals and the different SERDES data paths for parallel/MIPI. 

    Best Regards,

    Casey  

  • 0 in reply to Casey McCrea
    Prodigy 225 points

    Hi Casey,

    it is in a microseconds not milliseconds. it will be still ok?

    have you any example for Framesync configuration (duty cycle, register configuration, etc.) that can be used on the TI954 that accommodate the TI913A and TI953 while considering the design shown in my previous message? i'm looking at a 30FPS per camera.

    thank you and best regards,

    omar

  • 0 in reply to omar chakroun
    TI__Guru** 103215 points

    Hello Omar,

    Sorry I misread - still 200us should be no problem. 

    For a code example of generating internal frame sync, please see 954 datasheet section 7.4.27.2

    To map that frame sync signal from one hub to the next, please see section 7.4.13.2 in the 954 datasheet for GPIO configuration. Set the desired GPIO output source to internally generated frame sync

    To then forward that received GPIO frame sync to the other camera, see datasheet section 7.4.27.1 for forwarding external frame sync.

    There is no specific considerations that need to be made for the above given that one sensor is DVP and the other is CSI-2 aside from the basic general configuration for each hub to strap the MODE pin for the correct expected serializer which also sets the back channel speeds.

    Best Regards,

    Casey 

  • 0 in reply to Casey McCrea
    Prodigy 225 points

    Hi Casey,

    Thank you for the reply and for the references on the documentation.

    I'll double check that and get back if needed.

    Thank you again and best regards,

    Omar