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TM4C1290NCPDT: Interrupt on line changes via Hardware QEI Interface

Chris Yorkey
Genius 16035 points
Part Number: TM4C1290NCPDT


TI Friends & Family,

Our customer is doing some work on a steering controller. They want to be able to time the A/B pulses coming into the system through the hardware QEI interface on a TI TM4C1290PDT controller.  They can get counts, velocity and everything else needed to report but there is no obvious way to interrupt on line changes. They understand they can with GPIOs as they actually do it to handle a second encoder.  Their thought is once they have enabled the special QEI mode on the pins, GPIO like handling is lost. 

So, regarding the QEI on the 1290PDT is this possible?  They are mostly looking for an estimate for firmware to support this and it may not be possible to do without a hardware change in fact.  But any comments or guidance is certainly welcomed.

Thank you and Viva La Tiva!

-Chris

  • 0
    TI__Guru**** 191906 points

    Hi Chris,

      Perhaps I'm not fully understanding the question. Can they not generate interrupts based on the direction change or other events?  Are they trying to generate interrupt based on the input edge? If they need to base on the input edge to generate interrupt then they can route their input to both the QEI and a different GPIO pin in parallel. 

  • 0 in reply to Charles Tsai
    TI__Genius 16035 points

    Charles,

    Thanks.  I believe they can generate interrupts based on the direction change and other events just fine. Yes it's by interrupt edge and what you describe below is a possibility, I think.  This is an existing design so they don't want to change hardware if at all possible. I will review with them as I think they may be able to use a cable mod rather than a board spin at least on the hardware side.  From a software perspective, I'll confirm this might offer a viable approach.

    Thanks,
    Chris