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MSP432E401Y: Interrupt Latency

Mike_d
Intellectual 1000 points
Part Number: MSP432E401Y
Other Parts Discussed in Thread: SYSBIOS

Hi,

I'm using the gpiointerrupt example from the drivers example.  I'm seeing a delay of the callback in the microseconds.  I didn't expect to see so much latency.  Is there some way to fix this?

Regards,

-Mike 

  • +1
    TI__Guru**** 191736 points

    Hi Mike,

      I'm running the same TI-RTOS example on TM4C129 device which is the same silicon as MSP432E. I don't have a MSP432E LaunchPad with me at the moment. I suppose your measurement is from the time the switch on the board is pressed until the callback function gpiobuttonFxn0 is entered, correct? See the below call stack where you see an interrupt will first start with ti_sysbios_family_arm_m3_Hwi_dispatch_I() and eventually call gpiobuttonFxn0. Several levels of function dispatching will elapse before gpiobuttonFxn0 is executed. I think if you want to measure the interrupt latency you should be measuring from the time an interrupt is asserted untilti_sysbios_family_arm_m3_Hwi_dispatch_ is entered. I'm not an TI-RTOS expert but I have heard about zero-latency interrupt that will be totally handled outside of BIOS but its use will be very restricted  in terms of the SYS/BIOS APIs they can invoke and thread safety must be carefully considered.