Recording time for which the button is pressed

Question

Hi, 
 I want to count the time in seconds for which I press the button and stop the counter when the button is released. How should I detect the long press of button and determine the time for which it was pressed ?
I have a nrf 51 development board. Any suggestions would be appreciated.

gortok · Accepted Answer

Here's a way to do it that uses the app_timer and the RTC1. This is for SDK 10. This is the method I use now. (I propose a second method below which I used yesterday, funny thing). 
 ###button_handler.c 
 #define BUTTON_DETECTION_DELAY APP_TIMER_TICKS(50, APP_TIMER_PRESCALER)

static uint32_t button_tick = 0;
static uint32_t button_tick_release = 0;
static uint32_t total_ticks = 0;

APP_TIMER_DEF(m_button_tick_timer);

static void button_handler(uint8_t button, uint8_t action)
{
	uint32_t err_code;
	switch(action) {
	case APP_BUTTON_PUSH:
 app_timer_start(m_button_tick_timer, 65535, NULL);
 err_code = app_timer_cnt_get(&button_tick);
 APP_ERROR_CHECK(err_code);
 break;
	case APP_BUTTON_RELEASE:
 err_code = app_timer_cnt_get(&button_tick_release);
 APP_ERROR_CHECK(err_code);
 
 err_code = app_timer_stop(m_button_tick_timer);
 APP_ERROR_CHECK(err_code);
 
 err_code = app_timer_cnt_diff_compute(button_tick_release, button_tick, &total_ticks);
 APP_ERROR_CHECK(err_code);
 SEGGER_RTT_printf(0, "total ticks was: %d
", total_ticks);
	break;
	}
}

static void timer_handler(void * p_context)
{
	UNUSED_PARAMETER(p_context);
	SEGGER_RTT_printf(0, "timer timed out");
}

void buttons_init(void)
{

	// Note: Array must be static because a pointer to it will be saved in the Button handler
	// module.
	uint32_t err_code = 0;

	static app_button_cfg_t buttons[] = {
 {BUTTON_PIN, APP_BUTTON_ACTIVE_LOW, NRF_GPIO_PIN_PULLUP, button_handler}
	};
	err_code = app_button_init((app_button_cfg_t *)buttons,
 sizeof(buttons) / sizeof(buttons[0]),
 BUTTON_DETECTION_DELAY);
	APP_ERROR_CHECK(err_code);
	err_code = app_button_enable();
	APP_ERROR_CHECK(err_code);

	err_code = app_timer_create(&m_button_tick_timer, APP_TIMER_MODE_REPEATED, timer_handler);
 
}
 
 ###way 2
Here's a way to do it if you don't care about it blocking. It isn't a good way. 
 ###button_handler.c 
 #define BUTTON_DETECTION_DELAY APP_TIMER_TICKS(100, APP_TIMER_PRESCALER)

static volatile uint16_t button_tick = 0;
static volatile uint16_t button_min_hand = 0;
static volatile bool button_pressed = false;

void buttons_init(void)
{
	uint32_t err_code = 0;
	static app_button_cfg_t buttons[] = {
 {BUTTON_PIN, APP_BUTTON_ACTIVE_LOW, NRF_GPIO_PIN_PULLUP, button_handler}
	};
	err_code = app_button_init((app_button_cfg_t *)buttons,
 sizeof(buttons) / sizeof(buttons[0]),
 BUTTON_DETECTION_DELAY);
	APP_ERROR_CHECK(err_code);
	err_code = app_button_enable();
	APP_ERROR_CHECK(err_code);

}

static void button_handler(uint8_t button, uint8_t action)
{

	switch(action) {
	case APP_BUTTON_PUSH:
 button_pressed = true;
 break;
	case APP_BUTTON_RELEASE:
 button_pressed = false;
 //SEGGER_RTT_printf(0, "button_ticks are: %d, button_min_hand is %d
", button_tick, button_min_hand);
 button_tick = 0;
 button_min_hand = 0;
 break;
	}
}

void button_tick_increment(void)
{
 if (button_pressed == true) {
 if (button_tick >= 65534) {
 button_min_hand++;
 button_tick = 0;
 }
 button_tick++;
	}
}
 
 ###main.c 
 #include "button_handler.h"
int main()
{
 buttons_init();
 for(;;) {
 button_tick_increment();
 }
}
 
 Effectively this lets me figure out how long the button has been held down by multiplying the " button_min_hand " by button_tick . As I said, there's probably a better way; but this works for my purposes (turning off the device if the button is held down for x seconds; or whatever).

Recording time for which the button is pressed

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