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DS90UB948-Q1: I2C transition is suffered by humid environment

Amelie Zheng
Genius 10865 points
Part Number: DS90UB948-Q1

Hi Team,

My customer now meet a really strange issue.

The touch IC work abnormally when the car power-up in the morning. The touch operation becomes very stuttered. But the display is normally.

When this occurred, customer found  that SCL pull down 2 second between 949 and Touch IC (path3), which also make path1's SCL pull down. During these 2 second, the touch operation becomes very stuttered and I2C bus has the error and noted that it can't find the touch IC. However, after 2 second, the I2C bus is reset automatically and then work normally.

Customer could repeat the issue by humidifying the connector B with a humidifier but couldn't repeat the issue when humidifying the connector A....it really strange.

So the reason why touch IC work abnormally is because I2C bus has error (SCLK pull-down). The reason why I2C bus has  error is because the coaxial between 949 and 948 connector B is humid. It is because customer is in Guangzhou, south china, now the weather is hot and rainy...

May I ask whether we have method to make sure the connection between 949 and 948 (path2) is good to transfer I2C data?

Software or hardware is ok....

 

  • 0
    TI__Mastermind 30515 points

    ameilie,

    1. you can read 948's reg., is it accessed? if yes, it means the link path2 is ok.

    2. please focus on why SCL is pulled to GND for 2s, you can isolate is it from sensor or from FPD-Link. the cooling in connector B is NOT root cause i think. but it could impact the SCL's level. anyway, you need identify which part is impacting this SCL.

    regards,

    Steven

  • 0 in reply to Steven(Shenzhen) Shi
    TI__Genius 10865 points

    Hi Steven,

    yes, I also understand as this way...But path 2 has back channel and forward channel.

    Because I2C and Video data are brought together 35 bit to transfer in Path 2. If Path 2 has problem, not only I2C but also Video data also will have issue, so I think the forward channel is ok and has no problem right?

    But what about the back channel?touch IC signal transfer to SOC is using the back channel... Maybe I should ask customer to run CRC?

  • 0 in reply to Steven(Shenzhen) Shi
    TI__Genius 10865 points

    And it is also very strange. Only humidify connector B, could customer repeat the issue...It seems if only humidify connector B, it only change the 948 status...

  • 0 in reply to Amelie Zheng
    TI__Mastermind 30515 points

    amilie,

    for I2C, it is on bi-direction, but video tranmission just is single, so it could be due to FC or BC issue.

    since this issue description is high level (such as humidy test..., connector ...), to make the issue more clearly, you need isolate which section is abnormal. or else we don't understand our chip issue just from this system level test.

    best regards,Steven