Hardware-Driven Interrupt wake-up

[Roger_PiSq]

Would like to know how quickly the nRF51822 evaluation board wakes-up, after receiving an external hardware interrupt.  Speifically, how fast can the evaluation begin making A/D measurements after waking-up from an external interrupt?  The initial conditions (I would think) would include setting-up the A/D prior to initiating sleep.  Would you please direct me to what examples there may be about hardware interrupt handling?  Thank you for your help.

[Jørgen Holmefjord]

Hi,

I assume you are talking about wakeup from System OFF sleep mode? The wakeup time is given in the product specifications:

If you want to measure time until you are done setting up ADC, you need to measure this yourself. Set a GPIO at the point where you are done with configuration, and measure the time between the interrupt pin rise and the GPIO using a logic analyzer.

In the SDK there is a pin change interrupt example, but this does not go to System OFF mode. These examples on our GitHub might be helpful.

Best regards,
Jørgen

[Roger_PiSq]

Thank you Jørgen.

I hadn't found the tOFF2ON reference you provided (OFF to CPU execute. 9.6 10.6μs).  I would have thought that "OFF" means not powered.  Is this a reference to interrupt driven wake-up time?

I had seen the "4.2 μs wake-up" (using 16 MHz RCOSC) and some nRF51822 wake-up blog discussions.  The difference between 9.6μs (OFF to CPU execute) and 4.2μs (wake-up) would make sense from the stand-point of less time needed for wakeup (than turn-on, from off) execution readiness.

If I have the right understanding of the basic difference between 4.2μs versus 9.6μs (see above), then I would like to know if "wake-up" also means that the CPU is ready to execute, with all system resources available and ready for immediate use.  (i.e. What is the state of readiness when wake-up has been achieved?)

Is there a timing diagram of A/D measurement initiation (by code) - to - A/D measurement completion?

I will do as you suggest, related to making specific timing measurements.  Thank you very much for your reply, and the examples.

-Roger