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nRF52840 startup time

jeppe86

Hi,

I have loaded a simple application on my nRF52840 that just activates a GPIO as soon as it reaches the main loop.

The SoC is powered externally according to the chapter "8.3.5 nRF52840 SoC direct supply" in nRF52840_DK_User_Guide_20201203.pdf.

When I measure the time between power on and GPIO high, I get around 70 ms:



Is there any way to decrease this time? I would like the nRF52840 to start in less than 10 ms.

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  • 0

    Hi again Jesper

    Do you have pin reset enabled? If so, can you measure the time to wake up there? The time from OFF to CPU execute accoridng to the product specification should only be 16.5us, se the Device startup times in the PS for more details.

    What might cause this is that your device is in debug mode. Please try power cycling your device entirely before doing this test to see if the startup is quicker that way. You can also try optimizing the application for speed in the optimization levels setting in SES.

    Best regards,

    Simon

  • 0 in reply to Simonr

    Hi again Simon,

    I'm only interested in the time between VDD on to CPU execute, so that is what I am focusing on. 

    The project was already in Release configuration, now I have changed the optimization level to level 2 (speed). Then I'm connecting 3.3V to P21 (External supply) and VIN on P20. The startup time (from VDD 1.8 V to GPIO high) is then 5.7 ms:

    I think this is fast enough.

    Best regards,

    Jesper

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  • 0 in reply to Simonr

    Hi again Simon,

    I'm only interested in the time between VDD on to CPU execute, so that is what I am focusing on. 

    The project was already in Release configuration, now I have changed the optimization level to level 2 (speed). Then I'm connecting 3.3V to P21 (External supply) and VIN on P20. The startup time (from VDD 1.8 V to GPIO high) is then 5.7 ms:

    I think this is fast enough.

    Best regards,

    Jesper

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