PX4-Autopilot/src/modules/land_detector/land_detector_main.cpp

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/**
 * @file land_detector_main.cpp
 * Land detection algorithm
 *
 * @author Johan Jansen <jnsn.johan@gmail.com>
 */

#include <px4_config.h>
#include <px4_defines.h>
#include <px4_tasks.h>
#include <px4_posix.h>
#include <unistd.h>					//usleep
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <drivers/drv_hrt.h>
#include <systemlib/systemlib.h>	//Scheduler
#include <systemlib/err.h>			//print to console

#include "FixedwingLandDetector.h"
#include "MulticopterLandDetector.h"

//Function prototypes
static int land_detector_start(const char *mode);
static void land_detector_stop();

/**
 * land detector app start / stop handling function
 * This makes the land detector module accessible from the nuttx shell
 * @ingroup apps
 */
extern "C" __EXPORT int land_detector_main(int argc, char *argv[]);

//Private variables
static LandDetector *land_detector_task = nullptr;
static char _currentMode[12];

/**
* Stop the task, force killing it if it doesn't stop by itself
**/
static void land_detector_stop()
{
	if (land_detector_task == nullptr) {
		warnx("not running");
		return;
	}

	land_detector_task->shutdown();

	// Wait for task to die
	int i = 0;

	do {
		/* wait 20ms */
		usleep(20000);

	} while (land_detector_task->isRunning() && ++i < 50);


	delete land_detector_task;
	land_detector_task = nullptr;
	warnx("land_detector has been stopped");
}

/**
* Start new task, fails if it is already running. Returns OK if successful
**/
static int land_detector_start(const char *mode)
{
	if (land_detector_task != nullptr) {
		warnx("already running");
		return -1;
	}

	//Allocate memory
	if (!strcmp(mode, "fixedwing")) {
		land_detector_task = new FixedwingLandDetector();

	} else if (!strcmp(mode, "multicopter")) {
		land_detector_task = new MulticopterLandDetector();

	} else {
		warnx("[mode] must be either 'fixedwing' or 'multicopter'");
		return -1;
	}

	//Check if alloc worked
	if (land_detector_task == nullptr) {
		warnx("alloc failed");
		return -1;
	}

	//Start new thread task
	int ret = land_detector_task->start();

	if (ret) {
		warnx("task start failed: %d", -errno);
		return -1;
	}

	/* avoid memory fragmentation by not exiting start handler until the task has fully started */
	const uint32_t timeout = hrt_absolute_time() + 5000000; //5 second timeout

	/* avoid printing dots just yet and do one sleep before the first check */
	usleep(10000);

	/* check if the waiting involving dots and a newline are still needed */
	if (!land_detector_task->isRunning()) {
		while (!land_detector_task->isRunning()) {

			printf(".");
			fflush(stdout);
			usleep(50000);

			if (hrt_absolute_time() > timeout) {
				warnx("start failed - timeout");
				land_detector_stop();
				return 1;
			}
		}

		printf("\n");
	}

	//Remember current active mode
	strncpy(_currentMode, mode, 12);

	return 0;
}

/**
* Main entry point for this module
**/
int land_detector_main(int argc, char *argv[])
{

	if (argc < 2) {
		goto exiterr;
	}

	if (argc >= 2 && !strcmp(argv[1], "start")) {
		if (land_detector_start(argv[2]) != 0) {
			warnx("land_detector start failed");
			return 1;
		}

		return 0;
	}

	if (!strcmp(argv[1], "stop")) {
		land_detector_stop();
		return 0;
	}

	if (!strcmp(argv[1], "status")) {
		if (land_detector_task) {

			if (land_detector_task->isRunning()) {
				warnx("running (%s): %s", _currentMode, (land_detector_task->isLanded()) ? "LANDED" : "IN AIR");

			} else {
				warnx("exists, but not running (%s)", _currentMode);
			}

			return 0;

		} else {
			warnx("not running");
			return 1;
		}
	}

exiterr:
	warnx("usage: land_detector {start|stop|status} [mode]");
	warnx("mode can either be 'fixedwing' or 'multicopter'");
	return 1;
}