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Original question:

BQ76942: DeepSleep mode wake up

BQ76942: EXIT DEEPSLEEP Issue

Sean Chan1
Prodigy 150 points
Part Number: BQ76942

Hi Matt,

When I use EXIT_DEEPSLEEP() cmd to make the chip get out of the deepsleep, I set ALARM Enable = 0xE080, and I want alert to tell me the measurement finished. But at the beginning when quit DEEPSLEEP, the alert works. And several seconds about 10s later, Alert signal disappear and never interrupts the MCU. 

Is there any special setting?

But if I use LD wakeup, there is no miss of Alert. Why? Very strange.

Should I use double EXIT_DEEPSLEEP() CMD to let the chip know it should run into NORMAL mode?

I need your help.

Thank you.

  • 0
    TI__Guru 54715 points

    Hi Sean,

    The deepsleep exit takes different times depending on how it is triggered, see the BQ76942 technical reference manual section 7.4 DEEPSLEEP Mode.

    If you get ALERT after writing ALARM ENABLE = 0xE080 it would seem one of those bits was already high.  Have you checked these?

  • 0 in reply to WM5295
    Prodigy 150 points

    Hi Matt,

    Too much time after I send  EXIT_DEEPSLEEP() CMD, then I get ALERT signal. And when I get Alert signal, I will readout ALARM status and clear all the bits which are set. But 10 seconds later, no more alert signal comes. And I read the ALARM status reg, it is 0x0.

  • 0 in reply to Sean Chan1
    TI__Guru 54715 points

    Hi Sean,

    You can send the Alarm Status clear command 0x62 and the Alarm Enable command 0x66 while in deep sleep mode. Then when you exit deep sleep you should see the alarm from the first event, hopefully FULLSCAN.

    Be sure you are clearing the the Alarm status and not the Alarm mask.  If the part wakes up it should scan again and you should see ALERT go high on the next FULLSCAN.  Also be sure you are not transitioning from DEEPSLEEP to SLEEP with a long voltage check time where FULLSCAN would be long delayed.