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DS90UB953-Q1: I2C control over multiple Serializer and Deserializes

Shinji Tsuji
Genius 14139 points
Part Number: DS90UB953-Q1

Hi team,

•Isn’t it possible for SoC in ECU unit to control CMOS Sensor in Camera Unit over additional UB953/954 in video splitter unit?
•If yes, could you advise how to assign addresses?
Please see attached system configuration and advise if this is possible or not?
regards,

DS90UB953 I2C daisy chain.pptx

  • 0
    TI__Genius 11340 points

    Hi Tsuji-san,

    Yes, it's possible. You'll need to set your IDs and aliases the following way:

  • 0
    TI__Mastermind 25955 points

    Hi Shinji,

    For the SOC in the ECU unit to send commands via I2C to the CMOS censor in the Camera Unit, please enable I2C passthrough mode and use slave aliases for each of the FPD link III portions of the signal chain.

    Letst first work backwards logically to determine address mappings from the CMOS sensor:

    Ensure the slave address used for the CMOS Sensor for the 953 and 954 in the Camera Unit / Video splitter unit map to the i2c address of the CMOS sensor.

    Ensure the slave address for used for the CMOS sensor for the 953 and 954 in the Video Splitter Unit / ECU map to slave address used for the CMOS Sensor for the 953 and 954 in the Camera Unit / Video splitter unit.

    Sincerely,
    Bryan Kahler

  • 0 in reply to Bryan Kahler
    TI__Genius 14139 points

    Hi Bryan,

    I'm little confused between Slave address and Slave Alias address.

    First of all, the image in Jiashow's reply is correct or not?

    regards,

  • 0 in reply to Shinji Tsuji
    TI__Genius 14139 points

    ?Hi Brian,

    I would like to monitor register value in CMOS image sensor chip through I2C between UB954_1 and UB953_1 by SoC in Video Splitter Unit.

    Isn't it possible to connect I2C pins of the SoC to this I2C bus?

    regards,

  • 0 in reply to Shinji Tsuji
    TI__Genius 11340 points

    Hi Tsuji-san,

    The way you have connected the I2C buses in the block diagram is correct. The difference between the slaveID and slaveAlias is that when the host sends a command to the slaveAlias, the device will look up this slaveAlias and see if it has a slaveID associated to it. If so, then the device sends it to the device with the slaveID.

    If you follow my diagram to set the slave ID and aliases you should be able to communicate to all the devices. Only communicate using the slave alias addresses.

    Best,

    Jiashow

  • 0 in reply to Shinji Tsuji
    TI__Mastermind 25955 points

    Hi Shinji,

    Yes, the addressing example given by Jiashow is correct.

    SLAVE_ID_N (where n is a value 0-7) refers to the actual i2c address of the device.
    SLAVE_ID_ALIAS_N refers to the new address mapping.

    Let's refer to the i2c network between the CMOS sensor and 953_2 as camera unit i2c network.

    Let's refer to the i2c network between the 954_2 (shown as 954_1 in the image above) and 953_1 as video splitter unit i2c network.  

    So for example (we will use N=3 for this device in this example), if the CMOS sensor has an i2c address of 0x20, set its SLAVE_ID_3 = 0x20 and set the corresponding SLAVE_ID_ALIAS_3 = 0x34.  These settings will be performed on the 954_2 via commands sent on the video splitter unit i2c network.

    This mapping will now cause i2c commands with an address of 0x20 on the camera unit i2c network to appear on the video splitter unit i2c network as 0x34.

    This describes the mapping of the CMOS sensor between these two aforementioned i2c networks.  Mapping may also be performed for commands between the video splitter unit i2c network and the ECU i2c network.

    It is possible to connect a SOC to the video splitter unit i2c network. Multi master is possible, but it will be up to your devices to properly handle the multi master arbitration across the 3 i2c nets.

    Sincerely,
    Bryan Kahler

  • 0 in reply to Bryan Kahler
    TI__Genius 14139 points

    Hi Bryan,

    Could you advise how long should I take the latency into account for FPD-Link video signals and I2C signals

    by UB953-1/954-1 in video splitter Unit?

    regards,

  • 0 in reply to Shinji Tsuji
    TI__Genius 11340 points

    Hi Tsuji-san,

    Local I2C communication latency is negligible compared to back channel latency. The I2C latency through the back channel is ~1us. So if there are two back channels, it'll be ~2us. 

    Best,

    Jiashow 

  • 0 in reply to Jiashow Ho
    TI__Genius 14139 points

    Hi Jiashow,

    Thank you.

    How long is the FPD-Link High speed signal's latency between them?

    BR

    Shinji

  • 0 in reply to Shinji Tsuji
    TI__Genius 11340 points

    Hi Tsuji-san,

    The forward channel latency is ~225ns.

    Best,

    Jiashow

  • 0 in reply to Jiashow Ho
    TI__Genius 14139 points

    Hi Jiashow,

    Do you mean the latency between 954 input to 953 output is ~225ns?

    regards,

  • 0 in reply to Shinji Tsuji
    TI__Genius 11340 points

    Hi Tsuji-san,

    Yes, that's correct.

    Best,

    Jiashow