Slow Wake-Up and Timer Start from Power Off

[LukeC]

Hello,

I am trying to set the nRF52 to power off and wake up on a momentary button push (scope measures momentary push logic low around 50ms-100ms). However, I am struggling to have my debounce timer start up fast enough to detect the button being still pressed. If I hold the button down for a longer press, 200ms+, then I am able to read the button pin as registering a press in my debounce timer. The nRF52 tOFF2ON is stated as 16.5us, so I am thinking the timer is not starting fast enough or the button pin is not setup quick enough? Any direction would be very helpful!

First I set up my button input and debounce timer:

int
main (void)
{
  uint32_t err_code;
  uint32_t time_ticks;
  uint32_t time_ms = 1; //Time(in miliseconds) between consecutive compare

  //Initialize.
  err_code = NRF_LOG_INIT(NULL);
  APP_ERROR_CHECK(err_code);

  /*********** Manual Input Config ******************/
  err_code = nrf_drv_gpiote_init ();
  APP_ERROR_CHECK(err_code);
  //nrf_drv_gpiote_in_config_t in_config = GPIOTE_CONFIG_IN_SENSE_HITOLO(true);
nrf_drv_gpiote_in_config_t in_config = GPIOTE_CONFIG_IN_SENSE_TOGGLE(false);
  in_config.pull = NRF_GPIO_PIN_PULLUP;
  err_code = nrf_drv_gpiote_in_init (BUTTON_1, &in_config, in_pin_handler);
  APP_ERROR_CHECK(err_code);
  nrf_drv_gpiote_in_event_enable (BUTTON_1, true);

  // Check initial button state
  if (button1_is_pressed())
    {
      btnpressed = 1;
    }

  /*********************************************/

  /*********** Timer Config ******************/
  nrf_drv_timer_config_t timer_cfg = NRF_DRV_TIMER_DEFAULT_CONFIG;
  err_code = nrf_drv_timer_init (&TIMER_LED, &timer_cfg,
				 timer_callback_handler);
  APP_ERROR_CHECK(err_code);
  time_ticks = nrf_drv_timer_ms_to_ticks (&TIMER_LED, time_ms);
  nrf_drv_timer_extended_compare (&TIMER_LED, NRF_TIMER_CC_CHANNEL0, time_ticks,
				  NRF_TIMER_SHORT_COMPARE0_CLEAR_MASK, true);
  nrf_drv_timer_enable (&TIMER_LED);
  /*****************************/

Here is my code to setup power off:

void
sleep_mode_enter (void)
{

  //uint32_t err_code;

  nrf_drv_gpiote_out_set (LED_1);

  //err_code = bsp_wakeup_button_enable(0);

  //err_code = nrf_gpio_cfg_sense_set( BUTTON_1, BUTTONS_ACTIVE_STATE ? NRF_GPIO_PIN_SENSE_HIGH :NRF_GPIO_PIN_SENSE_LOW );
  nrf_gpio_cfg_sense_set ( BUTTON_1, NRF_GPIO_PIN_SENSE_LOW);

  // Go to system-off mode (this function will not return; wakeup will cause a reset).
  nrf_drv_timer_compare_int_disable(&TIMER_LED,NRF_TIMER_CC_CHANNEL0);
  nrf_drv_timer_disable (&TIMER_LED);
  sd_power_system_off ();
//  err_code = sd_power_system_off ();
//  APP_ERROR_CHECK(err_code);
  while (1)
    ;
}

Here is my button debounce timer handler, after a short momentary push from wake-up, the system is seeing "state" as false, if I hold the button down for a long press it measures true.

void timer_callback_handler (nrf_timer_event_t event_type, void* p_context)
{
  static uint32_t button_debounce = 0;

  bool state;
  switch (event_type)
    {
    case NRF_TIMER_EVENT_COMPARE0:
      total_ticks++;
      state = button1_is_pressed();
      if (state && btnpressed) // Still held down
	{

[Ole Bauck]

You can do a quick test of the wake-up time, just toggle a pin at the start of your code and measure the distance between the falling edge that woke up your chip and the pin toggle. Doing this I got around 300us which is reasonable and much less than 50ms.

It seems to me that you are doing things in a hard way here. You know that the pin woke you up or a reset did it (see here). If you have multiple pins you can wake up from you can read them at startup to find out which one it was. Then you can start a timer to check the pin at a later point in time if the button/pin is still pushed. I would recommend using RTC instead of the TIMER as it draws a lot less current (1uA versus couple of 100uA). The app_timer module is easy to use for this purpose. If you have not used it before you can checkout this tutorial.

[LukeC]

Ole - Excellent comment, this worked. I am still a bit baffled as to why the app timer starts so much faster than a standard timer. I am able to go to full power down, press a button and catch the button pressed with a few debounce timer increments. Boosting a 200-300na off current with enthrall my client. Thanks!

[Ole Bauck]

Great that it worked!

The app_timer should not be faster than the timer in such a way that it should matter in this case, so I think it was something about the way you set up and used the timer. However I cannot see what was wrong. Anyway I guess we don't have find out if you are happy with the new solution.