Energy Modes - AN0007 - Application Note - Energy Micro

5 EM4 Wakeup Software Example
...the world's most energy friendly microcontrollers
This example shows how to do a wake up from EM4. It will also be shown how to make use of the 512
bytes of available memory that can be retained in EM4.
5.1 DK example
This example is made for the EFM32GG-DK3750/EFM32GG-DK3650 Development Kit. The example
will repeatedly enter EM4 and sleep for 5 seconds. A retention register is used to keep track of the
number of times the MCU has woken up from a BURTC interrupt.
It is also possible to wake up by connecting pin PF2 to GND. A separate register is used to keep track
of how many times the MCU has woken up from a GPIO pin.
Every time the MCU wakes up, the reset cause (reset pin, GPIO or BURTC) will be printed to the display.
The number of times woken up (for either GPIO or BURTC) is also printed. Make sure the AEM mode
is "EFM32" to enable the display (toggled with the AEM button).
5.2 STK example
This example is made for the EFM32GG-STK3700/EFM32GG-STK3600 Starter Kit. The example will
repeatedly enter EM4 and sleep for 5 seconds. A retention register is used to keep track of the number
of times the MCU has woken up from a BURTC interrupt.
It is also possible to wake up by connecting pin PF2 to GND. A separate register is used to keep track
of how many times the MCU has woken up from a GPIO pin. The PF2 pin is labelled SWO on the starter
kit and is found near the bottom right corner.
Every time the MCU wakes up, the reset cause (reset pin, GPIO or BURTC) will be printed to the LCD.
The number of times woken up (for either GPIO or BURTC) is also printed.
2013-05-08 - an0007_Rev1.07 10 www.energymicro.com