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PRU power consumption + Linux system wake up

ldufrechou
Intellectual 275 points

Hello,

I was reading Chli post on DEEP SLEEP power consumption.

OMAP-L138 Power Consumption in DEEPSLEEP

1/Do you have any idea of typical power consumption of one PRU unit running?

(something like deep sleep mode but with one PRU running to monitor external event and wake the DSP only)

I was thinking using one PRU to wake up the DSP on my system but I can't find any info on power hungryness of the solution.

 

2/Do you have any idea of waking up time for DSP when receiving event from PRU 

   And waking up time from deep sleep?

 

3/ In deep sleep mode, I think mDDR content is preserved?

If i well understood you can even select how much ram you want to preserve, right?

If yes, does it means that in deep sleep mode, system consume around 30mW but the Linux system can be waken up is less than < xxx ms?

 

Thanks for any feedback on these subjects.

Regards,

Laurent

  • 0
    TI__Expert 8785 points

    Pep said:

    1/Do you have any idea of typical power consumption of one PRU unit running?

    There is approximately 7mW increase in power consumption when running one PRU. 

    To re-emphasize what deepsleep mode does, it basically stops the crystal from oscillating and "freezes" the entire device.  The only communication to the device, when in deepsleep mode, is through the nDEEPSLEEP/RTC_ALARM pin.  You'll need an external signal or use the internal RTC to wake back up the device from deepsleep.

    The PRU is helpful whenever you want to reduce the overall active power.

     

    Pep said:

    2/Do you have any idea of waking up time for DSP when receiving event from PRU 

       And waking up time from deep sleep?

    I'm not sure what the latency would be to wake up the DSP after receiving the event from PRU.  Maybe someone else can help comment on it. 

    The wake up time from deepsleep will depend on how long it takes to relock the oscillator crystal and PLLs. 

     

    Pep said:

    3/ In deep sleep mode, I think mDDR content is preserved?

    If i well understood you can even select how much ram you want to preserve, right?

    If yes, does it means that in deep sleep mode, system consume around 30mW but the Linux system can be waken up is less than < xxx ms?

    In deepsleep mode, the mDDR contents will be preserved if the appropriate settings are selected (e.g., mDDR self refresh mode is selected).  With deepsleep, you should be able to wake back up faster than the initial boot up, but I'm not sure how much faster.  You can probably post to the Linux forum and ask if someone there has tried using deepsleep with a Linux system.

     

    --Christina