RE: RF interrupt on register retention

Håkon Alseth — Wed, 22 Jul 2015 13:52:56 GMT

Hi,

The only mode that can wakeup from RFIRQ is standby-mode (PWRDWN=7), as stated in the nRF24LE1 PS chapter 11.2.

You are entering a lower sleep mode, register retention, where the only clock source running is the 32 kHz source.

The reason why you need this sequence when in register retention (timer on):

PWRDWN = 7;
PWRDWN = 4;

is because the RTC peripheral wakes you up on a "pre start time" as it's named in the datasheet. This means that it wakes up the CPU core a given amount of 32 kHz cycles before the interrupt occurs so that you are able to start up your processes and the 16MHz external crystal for radio-usage.

Cheers, Håkon