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DS90UB935-Q1: I2C issue between DS90UB935 and DS90UB954

Betty Guo
Expert 7300 points
Part Number: DS90UB935-Q1


Hi team,

The test condition is IMX390+DS90UB935+DS90UB954+CPU, CPU integrate ISP.

Problems:

1. the I2C data of Deser can not be transfer to Ser correctly. and I2C voltage of Ser are be pull down about 250ms, see the belwo logic waveform:

2. Disable the back channel of 935/954, connect the I2C of CPU to sensor directly, after about one hour test, the I2C communication is normal. Before this I2C problem occured every few seconds.

could you help give some suggestions? and, if you need customer schematic, I can sent to you via emial.

thank you in advance.

  • 0
    TI__Genius 11340 points

    Hi Betty,

    Let me clarify, are you getting consistent lock between the Ser and Des (select RX port in reg 0x4C and check reg 0x4D)?

    Are you trying to talk to the camera? Or the 953? Is this running in sync or non-sync mode? What back channel did you set it to? 

    Best,

    Jiashow

  • 0 in reply to Jiashow Ho
    Prodigy 30 points

    Hi Jiashow,

    Thanks for you replay.

    Today we track the lock signal at Deser and found that it is normal high when processor communicate with sensor(imx390);

    And Then we measure i2c signal at Ser by oscilloscope, detected on the SDA signal there is many  spike pluse such as below;

    our device is runing in non-sync mode,and we dump register from ds90ub954:

  • 0 in reply to zhifeng yang
    TI__Genius 11340 points

    Hello,

    You're talking to the camera using the alias addr set in reg 0x65 right? Can you talk to the serializer okay?

    On register 0x4D, you're seeing lock change. Could you repeatedly read reg 0x4D and see if lock change disappears?

    Best,

    Jiashow

  • 0 in reply to Jiashow Ho
    Prodigy 30 points

    Hi Jiashow,

    we talk to the camera using the alias addr set in reg 0x65 and talk to serializer is okay.

    we did some test:

    1. ser/des is 953/954, everythink is ok.

    2. ser/des is 935/936, the i2c problem remains, and then we change reg 0x58's value 0x5A to 0x5D, it means we set bbc freq is 25mhz, i2c communication is normally ok.

    3. ser/des is 935/954, the i2c problem is always remains, but when we set bbc freq to 25mhz, The probability of problems is much lower.

    because our video is working all the time, so lock should not be change.

  • 0 in reply to zhifeng yang
    TI__Genius 11340 points

    Hi Zhifeng,

    Based on your observation, forward channel always works fine, but back channel is causing I2C issues from the des to ser. The back channel rate affects the I2C transactions?

    Are you reading CRC errors (reg 0x55, 0x56 in serializer)? Are you using PoC? What's your PoC network?

    Best,

    Jiashow

  • 0 in reply to Jiashow Ho
    Prodigy 30 points

    Hi Jiashow,

    According to your instruction, I read reg 0x55,0x56 in serializer,  found that there is back channel error, and the number of errors is slowly increasing.

    we using POC, the network and CRC error test result show below:

  • 0 in reply to zhifeng yang
    TI__Genius 11340 points

    Hi Zhifeng,

    Is it possible for you to probe the back channel (just disconnect the serializer and directly hook up the cable from the des to the scope)?

    Also, could you disable POC and power the ser board directly to see if the issue persists?

    Best,

    Jiashow