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DS90UB947-Q1: GPIO map error

user6064774
Prodigy 170 points
Part Number: DS90UB947-Q1

HI Ti：

    I usbed UB947-UB948 to Display.  GPIO0,2,3 map from 947-948 to control screen standby and Reset. But there are 4 equipments sometimes can not drive screen normal. I found the reason is GPIO0,2,3 of 948 map error（GPIO0,2,3 of 947 is high but GPIO0,2,3 of 948 is low). The register  GPIO0,2,3 of 948 are 0x1f=0x00 0x1d=0x10 0x1e=0x00 in error situation and  0x1f=0x95 0x1d=0x15 0x1e=0x51 in normal situation. I did ABA test of 947 and found the error situation follow the 947. So why set these registers error sometimes ?  Do you have any suggestions ？ Thanks.

  • 0
    TI__Guru** 108340 points

    Hello,

    I will look into this and come back to you on Tuesday.

  • 0 in reply to Hamzeh Jaradat
    TI__Guru** 108340 points

    Hello,

    There are multiple potential reasons:

    1) The 947 Power-up sequence is not as per our recommendations. i.e. You must keep all GPIOs low or high until after PDB is released.

    2) 947 I2C ready time is not maintained. i.e. maybe you are writing to the 947 immediately after Digital reset/PDB release without waiting min 2ms.

    3) you have not implemented the erratas from erratasheet.

    4) you are communication with the 948 and trying to configure its GPIOs before you have a stable LOCK.

    5) may be the transmission surrounding is noisy

  • 0 in reply to Hamzeh Jaradat
    Prodigy 170 points

    Thank you for your reply.  Power-up sequence is ok and I set 948 when lock is high. Erratas is included. I found map and screen is ok when I set back channel from 20 Mbps to 5 Mbps. why is it that ？Is this setting necessary ？

  • 0 in reply to user6064774
    TI__Guru** 108340 points

    Hello,

    I have not seen something like that befor!!

    Please make sure you have the correct settings and resistor values on MODE_SEL pins on both devices. Also please refer to 948 Datasheet section "7.3.9.2 Back Channel Configuration" and reg 0x23. And 947 d/s section "7.3.10.2 Back Channel Configuration".