text: /****************************************************************************
   *
   *   Copyright (c) 2015, 2016 Airmind Development Team. All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in
   *    the documentation and/or other materials provided with the
   *    distribution.
   * 3. Neither the name Airmind nor the names of its contributors may be
   *    used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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   ****************************************************************************/
  
  /**
   * @file srf02_i2c.cpp
   * @author Greg Hulands
   * @author Jon Verbeke <jon.verbeke@kuleuven.be>
   *
   * Driver for the Maxbotix sonar range finders connected via I2C.
   */
  
  #include <px4_config.h>
  #include <px4_defines.h>
  #include <px4_getopt.h>
  
  #include <drivers/device/i2c.h>
  
  #include <sys/types.h>
  #include <stdint.h>
  #include <stdlib.h>
  #include <stdbool.h>
  #include <semaphore.h>
  #include <string.h>
  #include <fcntl.h>
  #include <poll.h>
  #include <errno.h>
  #include <stdio.h>
  #include <math.h>
  #include <unistd.h>
  #include <vector>
  
  #include <nuttx/arch.h>
  #include <nuttx/wqueue.h>
  #include <nuttx/clock.h>
  
  #include <systemlib/perf_counter.h>
  #include <systemlib/err.h>
  
  #include <drivers/drv_hrt.h>
  #include <drivers/drv_range_finder.h>
  #include <drivers/device/ringbuffer.h>
  
  #include <uORB/uORB.h>
  #include <uORB/topics/subsystem_info.h>
  #include <uORB/topics/distance_sensor.h>
  
  #include <board_config.h>
  
  /* Configuration Constants */
  #define SRF02_I2C_BUS 		PX4_I2C_BUS_EXPANSION
  #define SRF02_I2C_BASEADDR 	0x70 /* 7-bit address. 8-bit address is 0xE0 */
  #define SRF02_DEVICE_PATH	"/dev/srf02"
  
  /* MB12xx Registers addresses */
  
  #define SRF02_TAKE_RANGE_REG	0x51		/* Measure range Register */
  #define SRF02_SET_ADDRESS_0	0xA0		/* Change address 0 Register */
  #define SRF02_SET_ADDRESS_1	0xAA		/* Change address 1 Register */
  #define SRF02_SET_ADDRESS_2	0xA5		/* Change address 2 Register */
  
  /* Device limits */
  #define SRF02_MIN_DISTANCE 	(0.20f)
  #define SRF02_MAX_DISTANCE 	(6.00f)
  
  #define SRF02_CONVERSION_INTERVAL 	100000 /* 60ms for one sonar */
  #define TICKS_BETWEEN_SUCCESIVE_FIRES 	100000 /* 30ms between each sonar measurement (watch out for interference!) */
  
  #ifndef CONFIG_SCHED_WORKQUEUE
  # error This requires CONFIG_SCHED_WORKQUEUE.
  #endif
  
  class SRF02_I2C : public device::I2C
  {
  public:
  	SRF02_I2C(uint8_t rotation = distance_sensor_s::ROTATION_DOWNWARD_FACING, int bus = SRF02_I2C_BUS,
  		  int address = SRF02_I2C_BASEADDR);
  	virtual ~SRF02_I2C();
  
  	virtual int 		init();
  
  	virtual ssize_t		read(struct file *filp, char *buffer, size_t buflen);
  	virtual int			ioctl(struct file *filp, int cmd, unsigned long arg);
  
  	/**
  	* Diagnostics - print some basic information about the driver.
  	*/
  	void				print_info();
  
  protected:
  	virtual int			probe();
  
  private:
  	uint8_t _rotation;
  	float				_min_distance;
  	float				_max_distance;
  	work_s				_work;
  	ringbuffer::RingBuffer		*_reports;
  	bool				_sensor_ok;
  	int					_measure_ticks;
  	bool				_collect_phase;
  	int					_class_instance;
  	int					_orb_class_instance;
  
  	orb_advert_t		_distance_sensor_topic;
  
  	perf_counter_t		_sample_perf;
  	perf_counter_t		_comms_errors;
  
  	uint8_t				_cycle_counter;	/* counter in cycle to change i2c adresses */
  	int					_cycling_rate;	/* */
  	uint8_t				_index_counter;	/* temporary sonar i2c address */
  	std::vector<uint8_t>	addr_ind; 	/* temp sonar i2c address vector */
  	std::vector<float>
  	_latest_sonar_measurements; /* vector to store latest sonar measurements in before writing to report */
  
  
  	/**
  	* Test whether the device supported by the driver is present at a
  	* specific address.
  	*
  	* @param address	The I2C bus address to probe.
  	* @return			True if the device is present.
  	*/
  	int					probe_address(uint8_t address);
  
  	/**
  	* Initialise the automatic measurement state machine and start it.
  	*
  	* @note This function is called at open and error time.  It might make sense
  	*       to make it more aggressive about resetting the bus in case of errors.
  	*/
  	void				start();
  
  	/**
  	* Stop the automatic measurement state machine.
  	*/
  	void				stop();
  
  	/**
  	* Set the min and max distance thresholds if you want the end points of the sensors
  	* range to be brought in at all, otherwise it will use the defaults SRF02_MIN_DISTANCE
  	* and SRF02_MAX_DISTANCE
  	*/
  	void				set_minimum_distance(float min);
  	void				set_maximum_distance(float max);
  	float				get_minimum_distance();
  	float				get_maximum_distance();
  
  	/**
  	* Perform a poll cycle; collect from the previous measurement
  	* and start a new one.
  	*/
  	void				cycle();
  	int					measure();
  	int					collect();
  	/**
  	* Static trampoline from the workq context; because we don't have a
  	* generic workq wrapper yet.
  	*
  	* @param arg		Instance pointer for the driver that is polling.
  	*/
  	static void			cycle_trampoline(void *arg);
  
  
  };
  
  /*
   * Driver 'main' command.
   */
  extern "C" { __EXPORT int srf02_i2c_main(int argc, char *argv[]);}
  
  SRF02_I2C::SRF02_I2C(uint8_t rotation, int bus, int address) :
  	I2C("MB12xx", SRF02_DEVICE_PATH, bus, address, 100000),
  	_rotation(rotation),
  	_min_distance(SRF02_MIN_DISTANCE),
  	_max_distance(SRF02_MAX_DISTANCE),
  	_reports(nullptr),
  	_sensor_ok(false),
  	_measure_ticks(0),
  	_collect_phase(false),
  	_class_instance(-1),
  	_orb_class_instance(-1),
  	_distance_sensor_topic(nullptr),
  	_sample_perf(perf_alloc(PC_ELAPSED, "srf02_i2c_read")),
  	_comms_errors(perf_alloc(PC_COUNT, "srf02_i2c_comms_errors")),
  	_cycle_counter(0),	/* initialising counter for cycling function to zero */
  	_cycling_rate(0),	/* initialising cycling rate (which can differ depending on one sonar or multiple) */
  	_index_counter(0) 	/* initialising temp sonar i2c address to zero */
  
  {
  	/* enable debug() calls */
  	_debug_enabled = false;
  
  	/* work_cancel in the dtor will explode if we don't do this... */
  	memset(&_work, 0, sizeof(_work));
  }
  
  SRF02_I2C::~SRF02_I2C()
  {
  	/* make sure we are truly inactive */
  	stop();
  
  	/* free any existing reports */
  	if (_reports != nullptr) {
  		delete _reports;
  	}
  
  	if (_class_instance != -1) {
  		unregister_class_devname(RANGE_FINDER_BASE_DEVICE_PATH, _class_instance);
  	}
  
  	/* free perf counters */
  	perf_free(_sample_perf);
  	perf_free(_comms_errors);
  }
  
  int
  SRF02_I2C::init()
  {
  	int ret = PX4_ERROR;
  
  	/* do I2C init (and probe) first */
  	if (I2C::init() != OK) {
  		return ret;
  	}
  
  	/* allocate basic report buffers */
  	_reports = new ringbuffer::RingBuffer(2, sizeof(distance_sensor_s));
  
  	_index_counter = SRF02_I2C_BASEADDR;	/* set temp sonar i2c address to base adress */
  	set_device_address(_index_counter);		/* set I2c port to temp sonar i2c adress */
  
  	if (_reports == nullptr) {
  		return ret;
  	}
  
  	_class_instance = register_class_devname(RANGE_FINDER_BASE_DEVICE_PATH);
  
  	/* get a publish handle on the range finder topic */
  	struct distance_sensor_s ds_report = {};
  
  	_distance_sensor_topic = orb_advertise_multi(ORB_ID(distance_sensor), &ds_report,
  				 &_orb_class_instance, ORB_PRIO_LOW);
  
  	if (_distance_sensor_topic == nullptr) {
  		DEVICE_LOG("failed to create distance_sensor object. Did you start uOrb?");
  	}
  
  	// XXX we should find out why we need to wait 200 ms here
  	usleep(200000);
  
  	/* check for connected rangefinders on each i2c port:
  	   We start from i2c base address (0x70 = 112) and count downwards
  	   So second iteration it uses i2c address 111, third iteration 110 and so on*/
  	for (unsigned counter = 0; counter <= MB12XX_MAX_RANGEFINDERS; counter++) {
  		_index_counter = SRF02_I2C_BASEADDR + counter * 2;	/* set temp sonar i2c address to base adress - counter */
  		set_device_address(_index_counter);			/* set I2c port to temp sonar i2c adress */
  		int ret2 = measure();
  
  		if (ret2 == 0) { /* sonar is present -> store address_index in array */
  			addr_ind.push_back(_index_counter);
  			DEVICE_DEBUG("sonar added");
  			_latest_sonar_measurements.push_back(200);
  		}
  	}
  
  	_index_counter = SRF02_I2C_BASEADDR;
  	set_device_address(_index_counter); /* set i2c port back to base adress for rest of driver */
  
  	/* if only one sonar detected, no special timing is required between firing, so use default */
  	if (addr_ind.size() == 1) {
  		_cycling_rate = SRF02_CONVERSION_INTERVAL;
  
  	} else {
  		_cycling_rate = TICKS_BETWEEN_SUCCESIVE_FIRES;
  	}
  
  	/* show the connected sonars in terminal */
  	for (unsigned i = 0; i < addr_ind.size(); i++) {
  		DEVICE_LOG("sonar %d with address %d added", (i + 1), addr_ind[i]);
  	}
  
  	DEVICE_DEBUG("Number of sonars connected: %d", addr_ind.size());
  
  	ret = OK;
  	/* sensor is ok, but we don't really know if it is within range */
  	_sensor_ok = true;
  
  	return ret;
  }
  
  int
  SRF02_I2C::probe()
  {
  	return measure();
  }
  
  void
  SRF02_I2C::set_minimum_distance(float min)
  {
  	_min_distance = min;
  }
  
  void
  SRF02_I2C::set_maximum_distance(float max)
  {
  	_max_distance = max;
  }
  
  float
  SRF02_I2C::get_minimum_distance()
  {
  	return _min_distance;
  }
  
  float
  SRF02_I2C::get_maximum_distance()
  {
  	return _max_distance;
  }
  
  int
  SRF02_I2C::ioctl(struct file *filp, int cmd, unsigned long arg)
  {
  	switch (cmd) {
  
  	case SENSORIOCSPOLLRATE: {
  			switch (arg) {
  
  			/* switching to manual polling */
  			case SENSOR_POLLRATE_MANUAL:
  				stop();
  				_measure_ticks = 0;
  				return OK;
  
  			/* external signalling (DRDY) not supported */
  			case SENSOR_POLLRATE_EXTERNAL:
  
  			/* zero would be bad */
  			case 0:
  				return -EINVAL;
  
  			/* set default/max polling rate */
  			case SENSOR_POLLRATE_MAX:
  			case SENSOR_POLLRATE_DEFAULT: {
  					/* do we need to start internal polling? */
  					bool want_start = (_measure_ticks == 0);
  
  					/* set interval for next measurement to minimum legal value */
  					_measure_ticks = USEC2TICK(_cycling_rate);
  
  					/* if we need to start the poll state machine, do it */
  					if (want_start) {
  						start();
  
  					}
  
  					return OK;
  				}
  
  			/* adjust to a legal polling interval in Hz */
  			default: {
  					/* do we need to start internal polling? */
  					bool want_start = (_measure_ticks == 0);
  
  					/* convert hz to tick interval via microseconds */
  					int ticks = USEC2TICK(1000000 / arg);
  
  					/* check against maximum rate */
  					if (ticks < USEC2TICK(_cycling_rate)) {
  						return -EINVAL;
  					}
  
  					/* update interval for next measurement */
  					_measure_ticks = ticks;
  
  					/* if we need to start the poll state machine, do it */
  					if (want_start) {
  						start();
  					}
  
  					return OK;
  				}
  			}
  		}
  
  	case SENSORIOCGPOLLRATE:
  		if (_measure_ticks == 0) {
  			return SENSOR_POLLRATE_MANUAL;
  		}
  
  		return (1000 / _measure_ticks);
  
  	case SENSORIOCSQUEUEDEPTH: {
  			/* lower bound is mandatory, upper bound is a sanity check */
  			if ((arg < 1) || (arg > 100)) {
  				return -EINVAL;
  			}
  
  			irqstate_t flags = px4_enter_critical_section();
  
  			if (!_reports->resize(arg)) {
  				px4_leave_critical_section(flags);
  				return -ENOMEM;
  			}
  
  			px4_leave_critical_section(flags);
  
  			return OK;
  		}
  
  	case SENSORIOCGQUEUEDEPTH:
  		return _reports->size();
  
  	case SENSORIOCRESET:
  		/* XXX implement this */
  		return -EINVAL;
  
  	case RANGEFINDERIOCSETMINIUMDISTANCE: {
  			set_minimum_distance(*(float *)arg);
  			return 0;
  		}
  		break;
  
  	case RANGEFINDERIOCSETMAXIUMDISTANCE: {
  			set_maximum_distance(*(float *)arg);
  			return 0;
  		}
  		break;
  
  	default:
  		/* give it to the superclass */
  		return I2C::ioctl(filp, cmd, arg);
  	}
  }
  
  ssize_t
  SRF02_I2C::read(struct file *filp, char *buffer, size_t buflen)
  {
  
  	unsigned count = buflen / sizeof(struct distance_sensor_s);
  	struct distance_sensor_s *rbuf = reinterpret_cast<struct distance_sensor_s *>(buffer);
  	int ret = 0;
  
  	/* buffer must be large enough */
  	if (count < 1) {
  		return -ENOSPC;
  	}
  
  	/* if automatic measurement is enabled */
  	if (_measure_ticks > 0) {
  
  		/*
  		 * While there is space in the caller's buffer, and reports, copy them.
  		 * Note that we may be pre-empted by the workq thread while we are doing this;
  		 * we are careful to avoid racing with them.
  		 */
  		while (count--) {
  			if (_reports->get(rbuf)) {
  				ret += sizeof(*rbuf);
  				rbuf++;
  			}
  		}
  
  		/* if there was no data, warn the caller */
  		return ret ? ret : -EAGAIN;
  	}
  
  	/* manual measurement - run one conversion */
  	do {
  		_reports->flush();
  
  		/* trigger a measurement */
  		if (OK != measure()) {
  			ret = -EIO;
  			break;
  		}
  
  		/* wait for it to complete */
  		usleep(_cycling_rate * 2);
  
  		/* run the collection phase */
  		if (OK != collect()) {
  			ret = -EIO;
  			break;
  		}
  
  		/* state machine will have generated a report, copy it out */
  		if (_reports->get(rbuf)) {
  			ret = sizeof(*rbuf);
  		}
  
  	} while (0);
  
  	return ret;
  }
  
  int
  SRF02_I2C::measure()
  {
  
  	int ret;
  
  	/*
  	 * Send the command to begin a measurement.
  	 */
  
  	uint8_t cmd[2];
  	cmd[0] = 0x00;
  	cmd[1] = SRF02_TAKE_RANGE_REG;
  	ret = transfer(cmd, 2, nullptr, 0);
  
  	if (OK != ret) {
  		perf_count(_comms_errors);
  		DEVICE_DEBUG("i2c::transfer returned %d", ret);
  		return ret;
  	}
  
  	ret = OK;
  
  	return ret;
  }
  
  int
  SRF02_I2C::collect()
  {
  	int	ret = -EIO;
  
  	/* read from the sensor */
  	uint8_t val[2] = {0, 0};
  	uint8_t cmd = 0x02;
  	perf_begin(_sample_perf);
  
  	ret = transfer(&cmd, 1, nullptr, 0);
  	ret = transfer(nullptr, 0, &val[0], 2);
  
  	if (ret < 0) {
  		DEVICE_DEBUG("error reading from sensor: %d", ret);
  		perf_count(_comms_errors);
  		perf_end(_sample_perf);
  		return ret;
  	}
  
  	uint16_t distance_cm = val[0] << 8 | val[1];
  	float distance_m = float(distance_cm) * 1e-2f;
  
  	struct distance_sensor_s report;
  	report.timestamp = hrt_absolute_time();
  	report.type = distance_sensor_s::MAV_DISTANCE_SENSOR_ULTRASOUND;
  	report.orientation = _rotation;
  	report.current_distance = distance_m;
  	report.min_distance = get_minimum_distance();
  	report.max_distance = get_maximum_distance();
  	report.covariance = 0.0f;
  	/* TODO: set proper ID */
  	report.id = 0;
  
  	/* publish it, if we are the primary */
  	if (_distance_sensor_topic != nullptr) {
  		orb_publish(ORB_ID(distance_sensor), _distance_sensor_topic, &report);
  	}
  
  	_reports->force(&report);
  
  	/* notify anyone waiting for data */
  	poll_notify(POLLIN);
  
  	ret = OK;
  
  	perf_end(_sample_perf);
  	return ret;
  }
  
  void
  SRF02_I2C::start()
  {
  
  	/* reset the report ring and state machine */
  	_collect_phase = false;
  	_reports->flush();
  
  	/* schedule a cycle to start things */
  	work_queue(HPWORK, &_work, (worker_t)&SRF02_I2C::cycle_trampoline, this, 5);
  
  	/* notify about state change */
  	struct subsystem_info_s info = {};
  	info.present = true;
  	info.enabled = true;
  	info.ok = true;
  	info.subsystem_type = subsystem_info_s::SUBSYSTEM_TYPE_RANGEFINDER;
  
  	static orb_advert_t pub = nullptr;
  
  	if (pub != nullptr) {
  		orb_publish(ORB_ID(subsystem_info), pub, &info);
  
  	} else {
  		pub = orb_advertise(ORB_ID(subsystem_info), &info);
  
  	}
  }
  
  void
  SRF02_I2C::stop()
  {
  	work_cancel(HPWORK, &_work);
  }
  
  void
  SRF02_I2C::cycle_trampoline(void *arg)
  {
  
  	SRF02_I2C *dev = (SRF02_I2C *)arg;
  
  	dev->cycle();
  
  }
  
  void
  SRF02_I2C::cycle()
  {
  	if (_collect_phase) {
  		_index_counter = addr_ind[_cycle_counter]; /*sonar from previous iteration collect is now read out */
  		set_device_address(_index_counter);
  
  		/* perform collection */
  		if (OK != collect()) {
  			DEVICE_DEBUG("collection error");
  			/* if error restart the measurement state machine */
  			start();
  			return;
  		}
  
  		/* next phase is measurement */
  		_collect_phase = false;
  
  		/* change i2c adress to next sonar */
  		_cycle_counter = _cycle_counter + 1;
  
  		if (_cycle_counter >= addr_ind.size()) {
  			_cycle_counter = 0;
  		}
  
  		/* Is there a collect->measure gap? Yes, and the timing is set equal to the cycling_rate
  		   Otherwise the next sonar would fire without the first one having received its reflected sonar pulse */
  
  		if (_measure_ticks > USEC2TICK(_cycling_rate)) {
  
  			/* schedule a fresh cycle call when we are ready to measure again */
  			work_queue(HPWORK,
  				   &_work,
  				   (worker_t)&SRF02_I2C::cycle_trampoline,
  				   this,
  				   _measure_ticks - USEC2TICK(_cycling_rate));
  			return;
  		}
  	}
  
  	/* Measurement (firing) phase */
  
  	/* ensure sonar i2c adress is still correct */
  	_index_counter = addr_ind[_cycle_counter];
  	set_device_address(_index_counter);
  
  	/* Perform measurement */
  	if (OK != measure()) {
  		DEVICE_DEBUG("measure error sonar adress %d", _index_counter);
  	}
  
  	/* next phase is collection */
  	_collect_phase = true;
  
  	/* schedule a fresh cycle call when the measurement is done */
  	work_queue(HPWORK,
  		   &_work,
  		   (worker_t)&SRF02_I2C::cycle_trampoline,
  		   this,
  		   USEC2TICK(_cycling_rate));
  
  }
  
  void
  SRF02_I2C::print_info()
  {
  	perf_print_counter(_sample_perf);
  	perf_print_counter(_comms_errors);
  	printf("poll interval:  %u ticks\n", _measure_ticks);
  	_reports->print_info("report queue");
  }
  
  /**
   * Local functions in support of the shell command.
   */
  namespace  srf02_i2c
  {
  
  SRF02_I2C	*g_dev;
  
  void	start(uint8_t rotation);
  void	stop();
  void	test();
  void	reset();
  void	info();
  
  /**
   * Start the driver.
   */
  void
  start(uint8_t rotation)
  {
  	int fd;
  
  	if (g_dev != nullptr) {
  		errx(1, "already started");
  	}
  
  	/* create the driver */
  	g_dev = new SRF02_I2C(rotation, SRF02_I2C_BUS);
  
  	if (g_dev == nullptr) {
  		goto fail;
  	}
  
  	if (OK != g_dev->init()) {
  		goto fail;
  	}
  
  	/* set the poll rate to default, starts automatic data collection */
  	fd = open(SRF02_DEVICE_PATH, O_RDONLY);
  
  	if (fd < 0) {
  		goto fail;
  	}
  
  	if (ioctl(fd, SENSORIOCSPOLLRATE, SENSOR_POLLRATE_DEFAULT) < 0) {
  		goto fail;
  	}
  
  	exit(0);
  
  fail:
  
  	if (g_dev != nullptr) {
  		delete g_dev;
  		g_dev = nullptr;
  	}
  
  	errx(1, "driver start failed");
  }
  
  /**
   * Stop the driver
   */
  void stop()
  {
  	if (g_dev != nullptr) {
  		delete g_dev;
  		g_dev = nullptr;
  
  	} else {
  		errx(1, "driver not running");
  	}
  
  	exit(0);
  }
  
  /**
   * Perform some basic functional tests on the driver;
   * make sure we can collect data from the sensor in polled
   * and automatic modes.
   */
  void
  test()
  {
  	struct distance_sensor_s report;
  	ssize_t sz;
  	int ret;
  
  	int fd = open(SRF02_DEVICE_PATH, O_RDONLY);
  
  	if (fd < 0) {
  		err(1, "%s open failed (try 'srf02_i2c start' if the driver is not running", SRF02_DEVICE_PATH);
  	}
  
  	/* do a simple demand read */
  	sz = read(fd, &report, sizeof(report));
  
  	if (sz != sizeof(report)) {
  		err(1, "immediate read failed");
  	}
  
  	warnx("single read");
  	warnx("measurement: %0.2f m", (double)report.current_distance);
  	warnx("time:        %llu", report.timestamp);
  
  	/* start the sensor polling at 2Hz */
  	if (OK != ioctl(fd, SENSORIOCSPOLLRATE, 2)) {
  		errx(1, "failed to set 2Hz poll rate");
  	}
  
  	/* read the sensor 5x and report each value */
  	for (unsigned i = 0; i < 5; i++) {
  		struct pollfd fds;
  
  		/* wait for data to be ready */
  		fds.fd = fd;
  		fds.events = POLLIN;
  		ret = poll(&fds, 1, 2000);
  
  		if (ret != 1) {
  			errx(1, "timed out waiting for sensor data");
  		}
  
  		/* now go get it */
  		sz = read(fd, &report, sizeof(report));
  
  		if (sz != sizeof(report)) {
  			err(1, "periodic read failed");
  		}
  
  		warnx("periodic read %u", i);
  		warnx("valid %u", (float)report.current_distance > report.min_distance
  		      && (float)report.current_distance < report.max_distance ? 1 : 0);
  		warnx("measurement: %0.3f", (double)report.current_distance);
  		warnx("time:        %llu", report.timestamp);
  	}
  
  	/* reset the sensor polling to default rate */
  	if (OK != ioctl(fd, SENSORIOCSPOLLRATE, SENSOR_POLLRATE_DEFAULT)) {
  		errx(1, "failed to set default poll rate");
  	}
  
  	errx(0, "PASS");
  }
  
  /**
   * Reset the driver.
   */
  void
  reset()
  {
  	int fd = open(SRF02_DEVICE_PATH, O_RDONLY);
  
  	if (fd < 0) {
  		err(1, "failed ");
  	}
  
  	if (ioctl(fd, SENSORIOCRESET, 0) < 0) {
  		err(1, "driver reset failed");
  	}
  
  	if (ioctl(fd, SENSORIOCSPOLLRATE, SENSOR_POLLRATE_DEFAULT) < 0) {
  		err(1, "driver poll restart failed");
  	}
  
  	exit(0);
  }
  
  /**
   * Print a little info about the driver.
   */
  void
  info()
  {
  	if (g_dev == nullptr) {
  		errx(1, "driver not running");
  	}
  
  	printf("state @ %p\n", g_dev);
  	g_dev->print_info();
  
  	exit(0);
  }
  
  } /* namespace */
  
  int
  srf02_i2c_main(int argc, char *argv[])
  {
  	// check for optional arguments
  	int ch;
  	int myoptind = 1;
  	const char *myoptarg = NULL;
  	uint8_t rotation = distance_sensor_s::ROTATION_DOWNWARD_FACING;
  
  
  	while ((ch = px4_getopt(argc, argv, "R:", &myoptind, &myoptarg)) != EOF) {
  		switch (ch) {
  		case 'R':
  			rotation = (uint8_t)atoi(myoptarg);
  			PX4_INFO("Setting distance sensor orientation to %d", (int)rotation);
  			break;
  
  		default:
  			PX4_WARN("Unknown option!");
  		}
  	}
  
  	/*
  	 * Start/load the driver.
  	 */
  	if (!strcmp(argv[myoptind], "start")) {
  		srf02_i2c::start(rotation);
  	}
  
  	/*
  	 * Stop the driver
  	 */
  	if (!strcmp(argv[myoptind], "stop")) {
  		srf02_i2c::stop();
  	}
  
  	/*
  	 * Test the driver/device.
  	 */
  	if (!strcmp(argv[myoptind], "test")) {
  		srf02_i2c::test();
  	}
  
  	/*
  	 * Reset the driver.
  	 */
  	if (!strcmp(argv[myoptind], "reset")) {
  		srf02_i2c::reset();
  	}
  
  	/*
  	 * Print driver information.
  	 */
  	if (!strcmp(argv[myoptind], "info") || !strcmp(argv[myoptind], "status")) {
  		srf02_i2c::info();
  	}
  
  	errx(1, "unrecognized command, try 'start', 'test', 'reset' or 'info'");
  }
  