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When returning from PM1/2, the sleep timer value (used by RTIMER_NOW()) is not up-to-date until a positive edge on the 32-kHz clock has been detected after the system clock restarted. To ensure an updated value is read, wait for a positive transition on the 32-kHz clock by polling the SYS_CTRL_CLOCK_STA.SYNC_32K bit, before reading the sleep timer value. Because of this RTIMER_NOW() fixup, lpm_exit() has to be called at the very beginning of ISRs waking up the SoC. This also ensures that all clocks and timers are enabled at the correct frequency and updated before using them following wake-up. Without this fix, etimers could sometimes (randomly, depending on timings) become ultra slow (observed from 10x to 40x slower than normal) if the system exited PM1/2 very often. This issue occurred more often with PM1. Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
The Contiki Operating System
Contiki is an open source operating system that runs on tiny low-power microcontrollers and makes it possible to develop applications that make efficient use of the hardware while providing standardized low-power wireless communication for a range of hardware platforms.
Contiki is used in numerous commercial and non-commercial systems, such as city sound monitoring, street lights, networked electrical power meters, industrial monitoring, radiation monitoring, construction site monitoring, alarm systems, remote house monitoring, and so on.
For more information, see the Contiki website: