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TMS320F28022-Q1: Is GPIO pin must to enable pullup?

Shuqing Zhou
Intellectual 1130 points
Part Number: TMS320F28022-Q1
Other Parts Discussed in Thread: SYSCONFIG

Tool/software:

Hi experts,

I ask this question for my customer:

In our TRM, it has below description:

1. Is that means for GPIO-capable pins, the GPIO internal PULLUP will be enable in boot? and other pin will be disable by default apart from some boot mode related pin(such as SCI or other pin)?

2. Is our application need to enable all pins to enable pullup? Because in 28002x TRM, it said we should enable pullup to let pin in known state if it's be connected externally, customer afraid it also exist risk in 28022. Is it need to keep the GPIO in known state or other peripheral pin also?

3. For AIO pin, it don't have internal pullup circuit, how to configure them if customer don't use it?

BRs

Shuqing

  • 0
    TI__Genius 14311 points

    Hi Shuqing,

    Shuqing Zhou said:
    Is that means for GPIO-capable pins, the GPIO internal PULLUP will be enable in boot? and other pin will be disable by default apart from some boot mode related pin(such as SCI or other pin)?

    To summarize the description, all GPIOs have internal pullup enabled by default at reset except AIOs (which don't have internal pullup circuitry) and EPWM-capable pins. For the boot mode pins (24 and 32 on most entry-performance devices and 72 and 84 on higher-performance devices) internal pull-up is enabled ONLY after reset

    Shuqing Zhou said:
    2. Is our application need to enable all pins to enable pullup? Because in 28002x TRM, it said we should enable pullup to let pin in known state if it's be connected externally, customer afraid it also exist risk in 28022. Is it need to keep the GPIO in known state or other peripheral pin also?

    This is a best-practices recommendation. You can notice in our example code from the SDK, this is done. Also if they are using SysConfig for pinmuxing and code generation, this will automatically be covered in the GPIO initialization based on what the GPIO is being used for

    Shuqing Zhou said:
    3. For AIO pin, it don't have internal pullup circuit, how to configure them if customer don't use it?

    For AIO pins, these are present on analog pins. You can refer to the datasheet for the device on best practice for unused analog pins in Section Connections for Unused Pins. For the most part, these are safe to be left disconnected or tied to VSSA

    Regards,

    Peter

  • 0 in reply to Peter Luong1
    TI__Intellectual 1130 points

    Hi Peter,

    Thanks for your reply.

    Let me double check:

    1. That means if I don't disable pullup all GPIOs in application code, it will keep pullup enable? That means if I don't use such this code ( GpioCtrlRegs.GPAPUD.all = 0x0000;) , that's will be fine?

    )

    Peter Luong1 said:
    all GPIOs have internal pullup enabled by default at reset except AIOs (which don't have internal pullup circuitry) and EPWM-capable pins.
  • 0 in reply to Shuqing Zhou
    TI__Genius 14311 points

    Hi Shuqing, 

    That should be the case

    Regards,

    Peter