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CCS/TMS320F28335: Issue reading values from GPIO pins using XINTF

Marcos Araque
Prodigy 30 points

Part Number: TMS320F28335
Other Parts Discussed in Thread: C2000WARE

Tool/software: Code Composer Studio

Hello all,

I am currently using the F28335 DSC for a project, but I am struggling to interface the device with an external 8 bit DAC using the XINTF. This is my first microcontroller, so I am learning as I go.

From what I understand, a read/write will trigger the XD bus to a high state, following the timing diagrams, after setting up the XINTF zones and timing configurations. The XD 16 bit data bus corresponds to the GPIO pins 64-79. How do you know which pin(s) is active to send information to the DAC? I am first using a scope to check all the pins as I write data to memory in zone 7 in a loop and it is writing to the memory successfully according to the Watch Window. However, I am not getting any output in the GPIO pins which I will be connecting to the DAC. Any suggestions as to what is wrong or where to move from here?

Thanks for your time,

Marcos

  • 0
    TI__Guru 62975 points

    Marco,

    You probably did not configure the MUX for the XINTF pins. There are XINTF examples that you can reference in C2000Ware such as: \C2000Ware_XXXX\device_support\f2833x\examples\xintf_run_from

    The MUX is also documented in the System Control Reference Guide.

    Also note that the XINTF is designed to interface with asynchronous memories and its behavior is rigid.  It may not be possible to use XINTF with the DAC if it does not emulate a memory.

    -Tommy

  • 0 in reply to tlee
    Prodigy 30 points

    Hi Tommy,

    Thank you for your reply. I was initializing the registers incorrectly, but I fixed them after looking at the reference code.

    However, I am a bit confused about what you mean regarding the DAC having to emulate a memory. Since I am writing to the memory in the XINTF zones, does this still apply? The DAC will be generating a voltage reference based on the value written into the XINTF. The XD bus connected to the GPIO pins will be delivering these signals. 

    Thanks,

    Marcos

  • 0 in reply to Marcos Araque
    TI__Guru 62975 points
    Marcos,

    I was just pointing out that the XINTF bus activity will follow a state machine that is meant to interface with external memories. If this is working for your DAC, then there is nothing to worry about.

    -Tommy
  • 0 in reply to tlee
    Prodigy 30 points

    Got it. Thanks!