How to keep GPIO status during extended sleep

Hi brent_zheng,

The state of the pin before going to sleep, is retained but not the configuration or the functionality of the pin. When the device wake's up the periph_init() function is called in order to re-configure the pins in each wakeup and the pins return their default application state. So, if any of the GPIOs is high before going to sleep, it will stay high during sleep, and will be reconfigured in wake up by the periph_init() function. Which is the default pin state?

Thanks, PM_Dialog

Hello

The GPIO electric state is retained thanks to a latch that is driven by the power manager. When sleep condition are met, the power manager raise-up the latch so the GPIO is not lost during sleep. At wake-up power manager does launch periph_init function.

GPIO electrical state is being retained at the pad level, the GPIO controller is not retained so the status of the GPIO must be restored in periph_init. By looking at the source code of sys_power_manager.c you will find several hooks for instance

// A user definable macro that allows application code to be added.
configPRE_SLEEP_PROCESSING( sleep_period );

that could be called before going to sleep thus allowing you to backup the GPIO states right before sleeping. By reprogramming these states in periph_init you will be able to maintain a stable state.

Difference between prvSetupHardware and periph_init is related to sleep mode. The first is called at start-up while the latter is called at each wake-up so you should split init of your peripherals between these two. The first shall receive AlwaysOn peripherals init while the latter shall receive any peripheral init that is not managed by adapters.

Best Regards