System off wakeup by release of key

Question

Hello, 
 I am developing a remote device which uses system off mode for idle state. I also have the condition where extra long press of any key that is beyond the long press timeout will force device to enter in system off mode. But due to this i am facing auto wakeup from system off which i dont want .So I found that any signal change to gpio pin that may be low to high or high to low is detect signal for that GPIO which is causing reset. My question is that Can we identify that system got wakeup due to press event or release event. ? 
 Gpio configuration used is 
 
 static void buttons_init(void)
{
 ret_code_t err_code;

 //The array must be static because a pointer to it will be saved in the button handler module.
 static app_button_cfg_t buttons[] =
 {
 {PAGE_SEL_KEY, false, BUTTON_PULL, button_event_handler},
 };

 err_code = app_button_init(buttons, ARRAY_SIZE(buttons),
 BUTTON_DETECTION_DELAY);
 APP_ERROR_CHECK(err_code);
 err_code = app_button_enable();
 APP_ERROR_CHECK(err_code);
} 
 Thanks and regards.

cbd · Accepted Answer

I'd be wary of storing key press data in flash as you'll be limiting the life of your flash and also drawing more current in order to write and erase data than you would potentially save. 
 I also don't see how it would get you around your issue as you would still react to the reset and then have to check flash value, GPIO value before trying to shutdown and the cycle would then potentially start over again again. 
 You can't set the sense of the GPIO detection if the GPIO line is already in that state as you will immediately get a detection trigger (from 52840 datasheet, but will be applicable to other MCUs): 
 Make sure that a pin is in a level that cannot trigger the sense mechanism before enabling it. The DETECT signal will go high immediately if the SENSE condition configured in the PIN_CNF registers is met when the sense mechanism is enabled. This will trigger a PORT event if the DETECT signal was low before enabling the sense mechanism. 
 Hence my suggestion of waiting until the button is released before triggering SYSTEM OFF. 
 I see that you are using the button app library code, so there is no reason why you can't capture time of button press and then time of button release in your button event handler. If the difference is greater than your long button press you can then trigger SYSTEM OFF.

System off wakeup by release of key

Top Replies