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How to configure GPIO pins to start low??

Dror Medini
Prodigy 190 points


Hello,

I am using CCS3.3 and I download from TI's site: sprc530 - which is the DSP2833x HeaderFiles & Examples SW. I am running the flash example program so my F28335 controlCARD works as a stand alone unit. I know how to configure the GPIO pins to be everything I want, but how can I configure them to be low when I turn on the controlCARD??

When the program starts I initiate the GPIO pins to be low but I want them to start low the minute I apply voltage (turn on the switch in my docking station).

 

Thank you in advance,

Dror

  • 0
    TI__Guru 64600 points

    This is not possible.  The GPIOs will default to a particular state upon the release of reset.  This happens to be in GPIO mode (ie. not a peripheral mode) and as inputs for GPIO Port A, B and C.  There are a group of GPIOs that also disable the internal pullup upon reset (ie. GPIO Port A[11:0]).  The other GPIO Port A[31:12], GPIO Port B and GPIO Port C enable the internal pullup upon reset.  This information is detailed in the TMS320x2833x System Cotnrol and Interrupts Reference Guide (SPRUFB0).

    Therefore, if you want certain nets on your board to be low during and just after reset, you will need to add an external pulldown resistor on those lines.  Keep in mind, this will increase your current draw as there will be a constant current path through the internal pullup resistor and the external pulldown resistor.