• State
  • Locked Locked
  • Replies 7 replies
  • Subscribers 34 subscribers
  • Views 362 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DS90UB941AS-Q1: I2C error in 941+948，but no error in 947+948

Amelie Zheng
Genius 10865 points
Part Number: DS90UB941AS-Q1

Hi Team,

Customer used 947+948 before and now change to 941+948. The two solutions have the same screen and the same resolution.

The question is when 947+948, no I2C error; but when using 941+948, has I2C error. When asking customer to have more strict  cable shield，I2C error could be disappear.

But the cable already SOP and have a lot of order and stock. So can't change cable now.

Why？the same screen/cable/resolution but 941 have I2C error.

Does it mean 947 is better than 941 considering noise interference？

  • 0
    TI__Guru 66810 points

    Hi Amelie, 

    Can you clarify the error being seen with the 941? Is it a literal I2C error, or specifically a lock/link error register being asserted? 

    Were any of the peripheral circuitry/passives also changed considerably when migrating from 947 to 941? 

    Regards, 

    Logan

  • 0
    Prodigy 30 points

    Hi,Logan Cummins,

        When the 941 access the slave unit 948,it will print I2C error probabilistically.We use the 948 I2C connect to the touch screen for read coordinates,if the date becomes lager,the I2C error will be appear immediately.

  • 0 in reply to guanhua Chou
    TI__Guru 66810 points

    Hi Amelie/Guanhua, 

    Can you share the schematics for both 941 and 947 implementations. Amelie, since this is the public forum, can you email them to me? 

    Also, can you share any script files that are used for each implementation? 

    Regards, 

    Logan

  • 0 in reply to Logan Cummins
    Prodigy 30 points

    Hi,Logan,

    The schematics like this.

     

     And,I can't find your email.Here is mine guanhua.zhou@ddpai.com. 

    If you need to check the register,please tell me which one you want.

  • 0 in reply to guanhua Chou
    TI__Guru 66810 points

    Hi Guanhua, 

    Thanks for the schematics, I still have a couple things I need clarified if you don't mind:

    Amelie Zheng said:
    When asking customer to have more strict  cable shield，I2C error could be disappear.

    Just to confirm, did the I2C error disappear when the cable/shielding was changed? 

    guanhua Chou said:
    The schematics like this.

    I don't see where the I2C pull ups are on these schematics. Can you clarify what the pull-up values are on each I2C pin, as well as if there are any additional capacitance/series resistance is being used.

    Regards, 

    Logan

  • 0 in reply to Logan Cummins
    Prodigy 30 points

    If the cable is very short,less than half a meter,it is good.Or,if the cable is shelding good each other，I2C  error could be disappear.As shown in the figure.

    we use the resistance value is 2.2K Ohm,pull up to 3.3 volts.There is a 33pF capacitance and 100 Ohm series resistance each I2C pin on the slave unit 948.

  • 0 in reply to guanhua Chou
    TI__Guru 66810 points

    Hi Guanhua, 

    Can you check the link detect/lock register status (0x0C) according to the Serializer when the remote I2C fail condition exists? I'd like to better understand if the issue is isolated to I2C errors only, or if there has been a drop in the link all together. 

    Also, have you performed a margin analysis test on the link? 

    Regards, 

    Logan