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CC2340R5: Timer start based on event trigger

Munan Xu
Expert 5420 points

Part Number: CC2340R5

Hello,

Is it possible to start a LGPT on a GPIO event? I see that you can start a capture/ compare on event, but it doesn't seem possible to actually start the counter based off the event system, is that understanding correct?

Munan

  • 0
    TI__Guru**** 220787 points

    Hello Munan,

    I can confirm what you're seeing, in that the only LGPT even fabric input is for the CnCFG.INPUT used in a capture/compare.  I believe you can use single-request DMA to have the GPIO trigger a 32-bit transfer (word) to the LGPT CTL register address.  What I am thinking of involves setting DMACH[6/7]SEL in the event fabric EVTSVT to 7/9/Ah (GPIO combined wake up interrupt or another IO / GPIO combined event).  Also see [IOC/GPIO]:EVTCFG in the TRM.

    I cannot recall a recent example or application of such a configuration, please let me know if you are struggling to implement this and we can discuss further.

    Regards,
    Ryan

  • 0 in reply to Ryan Brown1
    TI__Expert 5420 points

    Hey Ryan,

    Thanks for confirming, I will check with the customer but sounds like it may be more work than it's worth. Will update once I hear back.

    Munan

  • 0 in reply to Munan Xu
    TI__Guru**** 220787 points

    Sounds good Munan.  If the device is in low-power standby mode then the turnaround time for the GPIO interrupt to start the LGPT will likely be about 50 us, based on this previous E2E thread.  But DMA is going to require active power to operate so the turnaround would be less than 10 us from Idle to Active, in which case you are not saving much time from using DMA to prime the LGPT.

    Regards,
    Ryan