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CC3220SF-LAUNCHXL: Power up timing over 1sec

Edward Pang
Prodigy 120 points

Part Number: CC3220SF-LAUNCHXL
Other Parts Discussed in Thread: CC3220SF

Based on TI out_of_box example code (TI-RTOS / CCS), GPIO toggle is added for timing measurement.

void * mainThread( void *arg )
{
	int32_t RetVal ;
	pthread_attr_t      pAttrs;
	pthread_attr_t      pAttrs_spawn;
	struct sched_param  priParam;
	struct timespec     ts = {0};

	Board_initGPIO();

    /* Reset Timing Measurement */
    GPIO_write(Board_LED0, Board_LED_OFF);
    GPIO_write(Board_LED0, Board_LED_ON);
    GPIO_write(Board_LED0, Board_LED_OFF);

I measured three pins in CC3220SF launchpad, from top to bottom, Reset Swicth, CC3220 nReset, LED0 with timing below:

It takes 1.1s to toggle the GPIO after nReset. 

From data sheet, it takes 3+25+17.3+4096*0.06 = 248.5ms to start first app code in worst case.  (I guess firmware size should be less than 4MB now)

My Question

May I know that 1.1s is best case of CC3220?  how to optimize it?  what's it doing after nReset?

  • 0
    TI__Mastermind 31055 points
    Hi Edward,

    What you are measuring at 1.1s is the wake-up time from shutdown mode for the device when using 32KHz XTAL. The timing you are listing here is if an external 32KHz clock is used. The additional wake-up time you have measured is due to the oscillator settling time.

    So you could reduce the time by using an external 32KHz clock source on your board to speed up the wake-up from shutdown or you can consider using hibernate (4uA) instead of shutdown as your main low-power mode. Wake-up from hibernate is very fast and the amount of power saved between using shutdown vs. hibernate is not very much once you consider the extra wake-up latency.

    Best Regards,
    Ben M
  • 0 in reply to Benjamin Moore
    Prodigy 120 points

    Hi Benjamin,

    Following your suggestion, I modified GPIO toggle code in Power Measure example using Hibernation command.

    From SW2 (P04) trigger to GPIO toggle, delay is 32.7ms.  The 1.1s 32KHz XTAL ready time is gone.  Thx

    New Question

    How to enable external 32KHz XTAL? Any API or example code?

    Thx & Regards,

    Edward

  • 0 in reply to Edward Pang
    TI__Mastermind 31055 points

    Hi Edward,

    There is no software change required. You can provide the device with an external 32KHz clock to be used as the slow clock by following section 4.14.4.2 of the CC3220 datasheet.

    Best Regards,

    Ben M

  • 0 in reply to Benjamin Moore
    Prodigy 120 points

    Hi Benjamin,

    I'm using CC3220SF-LAUNCHXL, and 32KHz crystal is placed by default.

    I checked that Y2 32KHz waveform is available on my hardware, and there's no jumper between xtal and CC3220SF according to schematic diagram.

    If software setting is not required, why the power-up time is still 1.1s?

    Regards,
    Edward

  • 0 in reply to Edward Pang
    TI__Mastermind 31055 points
    Hi Edward,

    This crystal feeds the internal oscillator which generates the slow-clock. This is what is referred to in section 4.14.3.1 of the datasheet.

    The second option (external 32kHz clock) refers to if you bypass the internal oscillator and provide a clock generated elsewhere in your system (that meets the slow clock requirements) to the chip.

    Best Regards,
    Ben M