i m using nrf51.... first i have call WFI(); and device goes to sleep mode...and when press any switch on gpio so, wack-up again...so, may i know that.. how many way for wack-up my chip.....like as.. switch press, interrupt call, and other.. i m not know other more.. just i m implement in RTC alarm system.. when set one time for alarm and match that time so chip wack-up and send message and sleep again... but now work on different wack-up cases..