SAM L21 Xplained Pro
This example demonstrates how to use the power driver. BUTTON0 is used to wake up the system from the standby sleep mode and as an external wakeup pin to wake up the system from the backup sleep mode. The wakeup pin level is low. The I/O pins PB22/PB23 are used as GCLK0/GCLK1 outputs so that an oscilloscope can be used to monitor the clock frequencies.
After power-on-reset (POR), GCLK0 and GCLK1 runs at 4MHz and LED0 is turned on. After one second, LED0 is turned off and the system enters standby sleep mode. BUTTON0 can then be used to wake up the system. After the system wakeup, LED0 is turned on, the performance level is switched to PL2, and the GCLK0 is increased to 48MHz. Further LED0 toggles two times and is turned off before the system enters BACKUP.
When BUTTON0 pushes, it connects to low level, system wakes up from the backup sleep mode, LED0 toggles four times. GCLK0/GCLK1 are running at 4MHz.