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DS90UB928Q-Q1: Is GPIO(Input type) valid when OEN = "L"?

Roy Chou1
Genius 17160 points

Part Number: DS90UB928Q-Q1

Tool/software:

Hi Team,

As title, I want to check if GPIO(input) can be worked when OEN = "L"? Same question for INTB_IN.

In below table, I see OUTPUTS on table and I am not sure if it affect input.

Regards,

Roy

  • 0
    TI__Genius 17160 points

    Hi Team,

    One additional question, in addition to OEN pin, do we have another method can disable the 928Q-Q1 LVDS output?

    Regards,

    Roy

  • 0 in reply to Roy Chou1
    TI__Genius 16420 points

    Hi Roy,

    To enable GPIO and INTB_IN pins, both OEN and OSS_SEL should be high. To disable the 928 LVDS output, you can also control these two signals using the override function in register 0x02. When the OEN and OSS_SEL are in the 'L' state, the pulldown is active for the GPIOs and the INTB_IN.

    Hope this helps,

    Esther

  • 0 in reply to Esther Chang
    TI__Genius 17160 points

    Hi Esther,

    Thank you for your comments.

    1. Do we have method that can disable the 928Q-Q1 LVDS output, but the INTB_IN and GPIO could be continuously work?

    2. My customer used the 947 + 928 to do the test. The OSS_SEL = 'H' and the OEN = 'L'. 

    We found the 928 GPIO can be worked if the GPIO configured as input type. 

    And the 928 GPIO can't be worked if the GPIO configured as output type. 

    Does the result normal to you?

    Regards,

    Roy

  • 0 in reply to Roy Chou1
    TI__Genius 16420 points

    Hi Roy,

    1. No.

    2. To answer your question, I need a little more clarification. When you configure the 928 GPIO, is it using a local device (directly connected to the 928 GPIO pins) or using the 947 GPIOs through the FPD-link? 

    Esther

  • 0 in reply to Esther Chang
    TI__Genius 17160 points

    Hi Ester,

    Below is our setup.

    1. We used MCU on 947 side to configure the 947GPIOx as output and 928GPIOx input.

    2. Remain the OSS_SEL = 'H' and  set the OEN = 'L'.

    3. Give the state to 928GPIOx and 947 GPIOx can map the state from 928GPIOx.

    We are wondering if we can get the same result if we used the 927 as serilalizer. (We don't have 927EVM to do the test.)

    Regards,

    Roy

  • 0 in reply to Roy Chou1
    TI__Genius 16420 points

    Hi Roy,

    Roy Chou1 said:

    We found the 928 GPIO can be worked if the GPIO configured as input type. 

    And the 928 GPIO can't be worked if the GPIO configured as output type. 

    Does the result normal to you

    OSS_SEL and OEN must be set "H" in order for the physical GPIO pins to output. The result you see makes sense because the input is programmed through the FPD link from the MCU rather than the physical GPIO pins on the 928 side, so the 928 and 947 are able to communicate via back channel (947 output <-- 928 input). However, when sending signals in the forward channel (947 input--> 928 output), it won't work because while the 928 GPIO pins receive the data, the 928 GPIO pins are pulled low, since OEN is "L." This result is also expected for the 927.

    Hope this helps,

    Esther