Current consumption rtc-> ppi ->gpiote on nrf52

[butch]

This thread discusses the nrf51  devzone.nordicsemi.com/.../current-consumption-when-using-rtc-ppi-and-gpiote  It says that the PPI (for nrf51 chip revisions up to rev 3) keeps the 16mhz clock on, and that Nordic doesn't recommend this combination for low power.  Is that still true for the nrf52?

I am doing the same thing as that thread: using the rtc to generate an event, which the ppi connects to a gpiote out task, which toggles an out pin.  (all without cpu waking.)   If someone has not already measured the current consumption for this combination, then I will just go back to using an ISR ( rtc generates an interrupt, and the ISR toggles the pin using the GPIO device.  Current consumption is only the current of the sleeping mcu and rtc.)

The product specs don't seem to have an electrical specification for the PPI, nor a value for the current of a GPIOTE out channel.

[haakonsh]

Hey butch,

I've made a small application demonstrating PPI vs CPU interrupts. rtc_ppi_gpiote.zip

You have to compile the application with the definition USE_PPI to use PPI+GPIOTE.

I've also compared the current consumption between the two:
With PPI:

With CPU interrupt:

 

As you can see the difference is dramatic. The RTC interrupt will also be at the mercy of it's execution/preemption priority, whereas the PPI system is completely independent from the CPU state. 

Cheers,

Håkon.

[gilbertjuly]

Hi Håkon, you presented the "rtc_ppi_gpiote.zip", I wonder which version of the SDK you were using. I'd like to have it a try. Thank you.

Gilbert

[haakonsh]

I honestly don't remember :/