GPStracker/soft/autopause.c

/*
 * Auto-pause detection: shared between the firmware and gps-test-tool (see
 * autopause_wrapper.c), since it directly gates what ends up in
 * System.distance/elevation_gain/elevation_loss (excluded while paused) and
 * is a major part of what those tools' output actually looks like.
 */
#ifdef PC_BUILD
#include "../gps-test-tool/main.h"
#else
#include "main.h"
#endif

struct auto_pause_s auto_pause;

/* Resuming from a period of auto-pause because of apparent distance needs
 * more apparent movement than triggering the pause did in the first place:
 * position noise while genuinely stationary (multipath, poor sky view) can
 * still occasionally clear the plain auto_pause_dist threshold over enough
 * auto_pause_time windows, and unlike a false pause (which just costs one
 * quiet window before the speed-based check or the next window catches the
 * resume), a false resume pollutes the moving/stopped split and the
 * odometer for as long as it isn't caught. */
#define AUTO_PAUSE_RESUME_DIST_MULT_X100	150	/* 1.5x the configured distance threshold */

static void auto_unpause(void) {
	if (!System.tracking_auto_paused)
		return;
	System.tracking_auto_paused = 0;
	log_pause_event(0);
	beep(50, 4);
}

static void auto_pause_activate(void) {
	System.tracking_auto_paused = 1;
	/* Otherwise, speed-counter progress from just before this decision (e.g.
	 * 2 of the 3 consecutive above-threshold samples the resume check below
	 * wants) could carry over and complete on the very next sample,
	 * instantly flip-flopping straight back out of the pause this just
	 * activated. */
	auto_pause.speed_counter = 0;
	log_pause_event(1);
	beep(50, 3);
}

void auto_pause_process(void) {
	if (System.tracking_paused || !get_flag(CONFFLAG_AUTO_PAUSE)) { /* remove auto-pause */
		System.tracking_auto_paused = 0;
		auto_pause.prev_distance = System.distance;
		auto_pause.point_counter = 0;
		auto_pause.speed_counter = 0;
		return;
	}
	/* A poor/invalid fix must not be read as "moving": a single noisy sample
	 * (e.g. a low-satellite, high-HDOP fix briefly reporting tens of km/h,
	 * as seen on a real hike where reception dropped for a few seconds)
	 * could otherwise satisfy the "3 consecutive" debounce below on its own
	 * and resume a logger that is actually sitting still. Such a sample is
	 * simply ignored - neither counted towards, nor resetting, the
	 * consecutive-samples debounce - so it can't itself trigger a resume,
	 * but also can't erase real progress made by genuine movement. */
	if (gps_fix_trustworthy()) {
		if (System.speed >= System.conf.auto_pause_speed) { /* unpause when set speed is exceeded for 3 consecutive measurements */
			if (++auto_pause.speed_counter >= 3) {
				auto_pause.point_counter = 0;
				auto_pause.speed_counter = 0;
				auto_unpause();
				return;
			}
		} else {
			auto_pause.speed_counter = 0;
		}
	}
	if (++auto_pause.point_counter < System.conf.auto_pause_time)
		return;
	auto_pause.point_counter = 0;
	if (System.tracking_auto_paused) {
		unsigned long int resume_threshold = (unsigned long int)System.conf.auto_pause_dist
			* AUTO_PAUSE_RESUME_DIST_MULT_X100 / 100;
		if ((System.distance - auto_pause.prev_distance)/100 > resume_threshold)
			auto_unpause(); /* unpause when distance exceeded */
	} else {
		/* Net displacement over this window can be small even while genuinely
		 * moving throughout it - a winding path folding back on itself, or a
		 * short out-and-back - and pausing on that alone, only to have the
		 * very next sample or two immediately satisfy the speed-based resume
		 * above, is itself a spurious (if brief) pause. If the logger is
		 * already moving fast enough to resume on its own right now, don't
		 * pause it in the first place. */
		if ((System.distance - auto_pause.prev_distance)/100 <= System.conf.auto_pause_dist
			&& System.speed < System.conf.auto_pause_speed)
			auto_pause_activate(); /* pause: not enough net movement, and not currently moving fast */
	}
	auto_pause.prev_distance = System.distance;
}