vl53lxx.cpp

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 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
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/**
 * @file vl53lxx.cpp
 * @author Daniele Pettenuzzo
 *
 * Driver for the vl53lxx ToF Sensor from ST Microelectronics connected via I2C.
 */

#include <px4_config.h>
#include <px4_defines.h>
#include <px4_getopt.h>
#include <px4_workqueue.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 <stdio.h>
#include <math.h>
#include <unistd.h>

#include <perf/perf_counter.h>

#include <drivers/drv_hrt.h>
#include <drivers/drv_range_finder.h>
#include <drivers/device/ringbuffer.h>

#include <uORB/uORB.h>
#include <uORB/topics/distance_sensor.h>

#include <board_config.h>

/* Configuration Constants */
#define VL53LXX_BUS_DEFAULT PX4_I2C_BUS_EXPANSION

#define VL53LXX_BASEADDR 0b0101001 // 7-bit address
#define VL53LXX_DEVICE_PATH "/dev/vl53lxx"

/* VL53LXX Registers addresses */
#define VHV_CONFIG_PAD_SCL_SDA_EXTSUP_HW_REG 0x89
#define MSRC_CONFIG_CONTROL_REG 0x60
#define FINAL_RANGE_CONFIG_MIN_COUNT_RATE_RTN_LIMIT_REG 0x44
#define SYSTEM_SEQUENCE_CONFIG_REG 0x01
#define DYNAMIC_SPAD_REF_EN_START_OFFSET_REG 0x4F
#define DYNAMIC_SPAD_NUM_REQUESTED_REF_SPAD_REG 0x4E
#define GLOBAL_CONFIG_REF_EN_START_SELECT_REG 0xB6
#define GLOBAL_CONFIG_SPAD_ENABLES_REF_0_REG 0xB0
#define SYSTEM_INTERRUPT_CONFIG_GPIO_REG 0x0A
#define SYSTEM_SEQUENCE_CONFIG_REG 0x01
#define SYSRANGE_START_REG 0x00
#define RESULT_INTERRUPT_STATUS_REG 0x13
#define SYSTEM_INTERRUPT_CLEAR_REG 0x0B
#define GLOBAL_CONFIG_SPAD_ENABLES_REF_0_REG 0xB0
#define GPIO_HV_MUX_ACTIVE_HIGH_REG 0x84
#define SYSTEM_INTERRUPT_CLEAR_REG 0x0B
#define RESULT_RANGE_STATUS_REG 0x14
#define VL53LXX_RA_IDENTIFICATION_MODEL_ID 0xC0
#define VL53LXX_IDENTIFICATION_MODEL_ID 0xEEAA

#define VL53LXX_US 1000 /*  1ms */
#define VL53LXX_SAMPLE_RATE 50000 /* 50ms */

#define VL53LXX_MAX_RANGING_DISTANCE 2.0f
#define VL53LXX_MIN_RANGING_DISTANCE 0.0f

#ifndef CONFIG_SCHED_WORKQUEUE
# error This requires CONFIG_SCHED_WORKQUEUE.
#endif

class VL53LXX : public device::I2C
{
public:
	VL53LXX(uint8_t rotation = distance_sensor_s::ROTATION_DOWNWARD_FACING,
		int bus = VL53LXX_BUS_DEFAULT, int address = VL53LXX_BASEADDR);

	virtual ~VL53LXX();

	virtual int init();

	virtual ssize_t read(device::file_t *filp, char *buffer, size_t buflen);

	virtual int ioctl(device::file_t *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;
	work_s _work;
	ringbuffer::RingBuffer *_reports;
	bool _sensor_ok;
	int _measure_ticks;
	bool _collect_phase;
	bool _new_measurement;
	bool _measurement_started;

	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 _stop_variable;


	/**
	* Initialise the automatic measurement state machine and start it.
	*/
	void start();

	/**
	* Stop the automatic measurement state machine.
	*/
	void stop();

	/**
	* Perform a poll cycle; collect from the previous measurement
	* and start a new one.
	*/
	void cycle();
	int measure();
	int collect();

	int readRegister(uint8_t reg_address, uint8_t &value);
	int writeRegister(uint8_t reg_address, uint8_t value);

	int writeRegisterMulti(uint8_t reg_address, uint8_t *value, uint8_t length);
	int readRegisterMulti(uint8_t reg_address, uint8_t *value, uint8_t length);

	int sensorInit();
	bool spadCalculations();
	bool sensorTuning();
	bool singleRefCalibration(uint8_t byte);

	/**
	* 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 vl53lxx_main(int argc, char *argv[]);

VL53LXX::VL53LXX(uint8_t rotation, int bus, int address) :
	I2C("VL53LXX", VL53LXX_DEVICE_PATH, bus, address, 400000),
	_rotation(rotation),
	_reports(nullptr),
	_sensor_ok(false),
	_measure_ticks(0),
	_collect_phase(false),
	_new_measurement(true),
	_measurement_started(false),
	_class_instance(-1),
	_orb_class_instance(-1),
	_distance_sensor_topic(nullptr),
	_sample_perf(perf_alloc(PC_ELAPSED, "vl53lxx_read")),
	_comms_errors(perf_alloc(PC_COUNT, "vl53lxx_com_err")),
	_stop_variable(0)
{
	// up the retries since the device misses the first measure attempts
	I2C::_retries = 3;

	// enable debug() calls
	_debug_enabled = false;

	// work_cancel in the dtor will explode if we don't do this...
	memset(&_work, 0, sizeof(_work));
}

VL53LXX::~VL53LXX()
{
	/* make sure we are truly inactive */
	stop();

	/* free any existing reports */
	if (_reports != nullptr) {
		delete _reports;
	}

	if (_distance_sensor_topic != nullptr) {
		orb_unadvertise(_distance_sensor_topic);
	}

	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
VL53LXX::sensorInit()
{
	uint8_t val = 0;
	int ret = OK;
	float rate_limit;
	uint8_t rate_limit_split[2];

	// I2C at 2.8V on sensor side of level shifter
	ret |= readRegister(VHV_CONFIG_PAD_SCL_SDA_EXTSUP_HW_REG, val);

	if (ret != OK) {
		ret = PX4_ERROR;
		return ret;
	}

	ret |= writeRegister(VHV_CONFIG_PAD_SCL_SDA_EXTSUP_HW_REG, val | 0x01);

	// set I2C to standard mode
	ret |= writeRegister(0x88, 0x00);

	ret |= writeRegister(0x80, 0x01);
	ret |= writeRegister(0xFF, 0x01);
	ret |= writeRegister(0x00, 0x00);
	ret |= readRegister(0x91, val);
	ret |= writeRegister(0x00, 0x01);
	ret |= writeRegister(0xFF, 0x00);
	ret |= writeRegister(0x80, 0x00);

	if (ret != OK) {
		ret = PX4_ERROR;
		return ret;
	}

	_stop_variable = val;

	// disable SIGNAL_RATE_MSRC (bit 1) and SIGNAL_RATE_PRE_RANGE (bit 4) limit checks
	readRegister(MSRC_CONFIG_CONTROL_REG, val);
	writeRegister(MSRC_CONFIG_CONTROL_REG, val | 0x12);

	// Set signal rate limit to 0.1
	rate_limit = 0.1 * 65536;
	rate_limit_split[0] = (((uint16_t)rate_limit) >> 8);
	rate_limit_split[1] = (uint16_t)rate_limit;

	writeRegisterMulti(FINAL_RANGE_CONFIG_MIN_COUNT_RATE_RTN_LIMIT_REG, &rate_limit_split[0], 2);
	writeRegister(SYSTEM_SEQUENCE_CONFIG_REG, 0xFF);

	spadCalculations();

	return ret;

}

int
VL53LXX::init()
{
	int ret = OK;

	set_device_address(VL53LXX_BASEADDR);

	/* do I2C init (and probe) first */
	if (I2C::init() != OK) {
		ret = PX4_ERROR;
		goto out;
	}

	/* allocate basic report buffers */
	_reports = new ringbuffer::RingBuffer(2, sizeof(distance_sensor_s));

	if (_reports == nullptr) {
		ret = PX4_ERROR;
		goto out;
	}

	_class_instance = register_class_devname(RANGE_FINDER_BASE_DEVICE_PATH);

	/* sensor is ok, but we don't really know if it is within range */
	_sensor_ok = true;

out:
	return ret;
}

int
VL53LXX::probe()
{
	if (sensorInit() == OK) {
		return OK;
	}

	// not found on any address
	return -EIO;
}

int
VL53LXX::ioctl(device::file_t *filp, int cmd, unsigned long arg)
{
	switch (cmd) {

	case SENSORIOCSPOLLRATE: {
			switch (arg) {

			case 0:
				return -EINVAL;

			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(VL53LXX_SAMPLE_RATE);

					/* if we need to start the poll state machine, do it */
					if (want_start) {
						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 */
					unsigned ticks = USEC2TICK(1000000 / arg);

					/* 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;
				}
			}
		}

	default:
		/* give it to the superclass */
		return I2C::ioctl(filp, cmd, arg);
	}
}


ssize_t
VL53LXX::read(device::file_t *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;
		}

		while (!_collect_phase);

		/* 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
VL53LXX::readRegister(uint8_t reg_address, uint8_t &value)
{
	int ret;

	/* write register address to the sensor */
	ret = transfer(&reg_address, sizeof(reg_address), nullptr, 0);

	if (OK != ret) {
		perf_count(_comms_errors);
		return ret;
	}

	/* read from the sensor */
	ret = transfer(nullptr, 0, &value, 1);

	if (OK != ret) {
		perf_count(_comms_errors);
		return ret;
	}

	return ret;

}


int
VL53LXX::readRegisterMulti(uint8_t reg_address, uint8_t *value, uint8_t length)
{
	int ret;

	/* write register address to the sensor */
	ret = transfer(&reg_address, 1, nullptr, 0);

	if (OK != ret) {
		perf_count(_comms_errors);
		return ret;
	}

	/* read from the sensor */
	ret = transfer(nullptr, 0, &value[0], length);

	if (OK != ret) {
		perf_count(_comms_errors);
		return ret;
	}

	return ret;

}


int
VL53LXX::writeRegister(uint8_t reg_address, uint8_t value)
{
	int ret;
	uint8_t cmd[2] = {0, 0};

	cmd[0] = reg_address;
	cmd[1] = value;

	ret = transfer(&cmd[0], 2, nullptr, 0);

	if (OK != ret) {
		perf_count(_comms_errors);
		return ret;
	}

	return ret;

}


int
VL53LXX::writeRegisterMulti(uint8_t reg_address, uint8_t *value,
			    uint8_t length) /* bytes are send in order as they are in the array */
{
	/* be careful: for uint16_t to send first higher byte */
	int ret;
	uint8_t cmd[7] = {0, 0, 0, 0, 0, 0, 0};

	if (length > 6 || length < 1) {
		DEVICE_LOG("VL53LXX::writeRegisterMulti length out of range");
		return PX4_ERROR;
	}

	cmd[0] = reg_address;

	memcpy(&cmd[1], &value[0], length);

	ret = transfer(&cmd[0], length + 1, nullptr, 0);

	if (OK != ret) {
		perf_count(_comms_errors);
		return ret;
	}

	return ret;

}


int
VL53LXX::measure()
{
	int ret = OK;
	uint8_t wait_for_measurement;
	uint8_t system_start;

	/*
	 * Send the command to begin a measurement.
	 */
	const uint8_t cmd = RESULT_RANGE_STATUS_REG + 10;

	if (_new_measurement) {

		_new_measurement = false;

		writeRegister(0x80, 0x01);
		writeRegister(0xFF, 0x01);
		writeRegister(0x00, 0x00);
		writeRegister(0x91, _stop_variable);
		writeRegister(0x00, 0x01);
		writeRegister(0xFF, 0x00);
		writeRegister(0x80, 0x00);

		writeRegister(SYSRANGE_START_REG, 0x01);

		readRegister(SYSRANGE_START_REG, system_start);

		if ((system_start & 0x01) == 1) {
			work_queue(LPWORK, &_work, (worker_t)&VL53LXX::cycle_trampoline, this,
				   USEC2TICK(VL53LXX_US));		// reschedule every 1 ms until measurement is ready
			ret = OK;
			return ret;

		} else {
			_measurement_started = true;
		}

	}

	if (!_collect_phase && !_measurement_started) {

		readRegister(SYSRANGE_START_REG, system_start);

		if ((system_start & 0x01) == 1) {
			work_queue(LPWORK, &_work, (worker_t)&VL53LXX::cycle_trampoline, this,
				   USEC2TICK(VL53LXX_US));		// reschedule every 1 ms until measurement is ready
			ret = OK;
			return ret;

		} else {
			_measurement_started = true;
		}
	}

	readRegister(RESULT_INTERRUPT_STATUS_REG, wait_for_measurement);

	if ((wait_for_measurement & 0x07) == 0) {
		work_queue(LPWORK, &_work, (worker_t)&VL53LXX::cycle_trampoline, this,
			   USEC2TICK(VL53LXX_US));		// reschedule every 1 ms until measurement is ready
		ret = OK;
		return ret;
	}

	_collect_phase = true;

	ret = transfer(&cmd, sizeof(cmd), nullptr, 0);

	if (OK != ret) {
		perf_count(_comms_errors);
		DEVICE_LOG("i2c::transfer returned %d", ret);
		return ret;
	}

	return ret;
}


int
VL53LXX::collect()
{
	int ret = -EIO;

	/* read from the sensor */
	uint8_t val[2] = {0, 0};

	perf_begin(_sample_perf);

	_collect_phase = false;

	ret = transfer(nullptr, 0, &val[0], 2);

	if (ret < 0) {
		DEVICE_LOG("error reading from sensor: %d", ret);
		perf_count(_comms_errors);
		perf_end(_sample_perf);
		return ret;
	}

	uint16_t distance_mm = (val[0] << 8) | val[1];
	float distance_m = float(distance_mm) *  1e-3f;
	struct distance_sensor_s report;

	report.timestamp = hrt_absolute_time();
	report.type = distance_sensor_s::MAV_DISTANCE_SENSOR_LASER;
	report.orientation = _rotation;

	report.current_distance = distance_m;

	report.min_distance = VL53LXX_MIN_RANGING_DISTANCE;
	report.max_distance = VL53LXX_MAX_RANGING_DISTANCE;
	report.variance = 0.0f;
	report.signal_quality = -1;

	/* TODO: set proper ID */
	report.id = 0;

	/* publish it, if we are the primary */
	if (_class_instance == CLASS_DEVICE_PRIMARY) {
		orb_publish_auto(ORB_ID(distance_sensor), &_distance_sensor_topic, &report, &_orb_class_instance,
				 ORB_PRIO_DEFAULT);
	}

	_reports->force(&report);

	/* notify anyone waiting for data */
	poll_notify(POLLIN);

	ret = OK;

	perf_end(_sample_perf);

	return ret;
}


void
VL53LXX::start()
{
	/* reset the report ring and state machine */
	_reports->flush();

	/* schedule a cycle to start things */
	work_queue(LPWORK, &_work, (worker_t)&VL53LXX::cycle_trampoline, this, USEC2TICK(VL53LXX_US));
}


void
VL53LXX::stop()
{
	work_cancel(LPWORK, &_work);
}


void
VL53LXX::cycle_trampoline(void *arg)
{
	VL53LXX *dev = (VL53LXX *)arg;

	dev->cycle();
}


void
VL53LXX::cycle()
{
	measure();

	if (_collect_phase) {

		_collect_phase = false;
		_new_measurement = true;

		collect();

		work_queue(LPWORK,
			   &_work,
			   (worker_t)&VL53LXX::cycle_trampoline,
			   this,
			   _measure_ticks);
	}

}


void
VL53LXX::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");
}


bool
VL53LXX::spadCalculations()
{
	uint8_t val;

	uint8_t spad_count;
	bool spad_type_is_aperture;

	uint8_t ref_spad_map[6];

	writeRegister(0x80, 0x01);
	writeRegister(0xFF, 0x01);
	writeRegister(0x00, 0x00);
	writeRegister(0xFF, 0x06);

	readRegister(0x83, val);
	writeRegister(0x83, val | 0x04);

	writeRegister(0xFF, 0x07);
	writeRegister(0x81, 0x01);
	writeRegister(0x80, 0x01);
	writeRegister(0x94, 0x6b);
	writeRegister(0x83, 0x00);

	readRegister(0x83, val);

	while (val == 0x00) {
		readRegister(0x83, val);
	}

	writeRegister(0x83, 0x01);

	readRegister(0x92, val);

	spad_count = val & 0x7f;
	spad_type_is_aperture = (val >> 7) & 0x01;

	writeRegister(0x81, 0x00);
	writeRegister(0xFF, 0x06);

	readRegister(0x83, val);
	writeRegister(0x83, val  & ~0x04);

	writeRegister(0xFF, 0x01);
	writeRegister(0x00, 0x01);
	writeRegister(0xFF, 0x00);
	writeRegister(0x80, 0x00);

	readRegisterMulti(GLOBAL_CONFIG_SPAD_ENABLES_REF_0_REG, &ref_spad_map[0], 6);

	writeRegister(0xFF, 0x01);
	writeRegister(DYNAMIC_SPAD_REF_EN_START_OFFSET_REG, 0x00);
	writeRegister(DYNAMIC_SPAD_NUM_REQUESTED_REF_SPAD_REG, 0x2C);
	writeRegister(0xFF, 0x00);
	writeRegister(GLOBAL_CONFIG_REF_EN_START_SELECT_REG, 0xB4);

	uint8_t first_spad_to_enable = spad_type_is_aperture ? 12 : 0;
	uint8_t spads_enabled = 0;

	for (uint8_t i = 0; i < 48; i++) {
		if (i < first_spad_to_enable || spads_enabled == spad_count) {
			ref_spad_map[i / 8] &= ~(1 << (i % 8));

		} else if ((ref_spad_map[i / 8] >> (i % 8)) & 0x1) {
			spads_enabled++;
		}
	}

	writeRegisterMulti(GLOBAL_CONFIG_SPAD_ENABLES_REF_0_REG, &ref_spad_map[0], 6);

	sensorTuning();

	writeRegister(SYSTEM_INTERRUPT_CONFIG_GPIO_REG, 4); 		// 4: GPIO interrupt on new data

	readRegister(GPIO_HV_MUX_ACTIVE_HIGH_REG, val);
	writeRegister(GPIO_HV_MUX_ACTIVE_HIGH_REG, val & ~0x10);  	// active low

	writeRegister(SYSTEM_INTERRUPT_CLEAR_REG, 0x01);

	writeRegister(SYSTEM_SEQUENCE_CONFIG_REG, 0xE8);

	writeRegister(SYSTEM_SEQUENCE_CONFIG_REG, 0x01);
	singleRefCalibration(0x40);

	writeRegister(SYSTEM_SEQUENCE_CONFIG_REG, 0x02);
	singleRefCalibration(0x00);

	writeRegister(SYSTEM_SEQUENCE_CONFIG_REG, 0xE8); 			// restore config

	return OK;

}


bool
VL53LXX::sensorTuning()
{

	writeRegister(0xFF, 0x01);
	writeRegister(0x00, 0x00);
	writeRegister(0xFF, 0x00);
	writeRegister(0x09, 0x00);
	writeRegister(0x10, 0x00);
	writeRegister(0x11, 0x00);
	writeRegister(0x24, 0x01);
	writeRegister(0x25, 0xFF);
	writeRegister(0x75, 0x00);
	writeRegister(0xFF, 0x01);
	writeRegister(0x4E, 0x2C);
	writeRegister(0x48, 0x00);
	writeRegister(0x30, 0x20);
	writeRegister(0xFF, 0x00);
	writeRegister(0x30, 0x09);
	writeRegister(0x54, 0x00);
	writeRegister(0x31, 0x04);
	writeRegister(0x32, 0x03);
	writeRegister(0x40, 0x83);
	writeRegister(0x46, 0x25);
	writeRegister(0x60, 0x00);
	writeRegister(0x27, 0x00);
	writeRegister(0x50, 0x06);
	writeRegister(0x51, 0x00);
	writeRegister(0x52, 0x96);
	writeRegister(0x56, 0x08);
	writeRegister(0x57, 0x30);
	writeRegister(0x61, 0x00);
	writeRegister(0x62, 0x00);
	writeRegister(0x64, 0x00);
	writeRegister(0x65, 0x00);
	writeRegister(0x66, 0xA0);
	writeRegister(0xFF, 0x01);
	writeRegister(0x22, 0x32);
	writeRegister(0x47, 0x14);
	writeRegister(0x49, 0xFF);
	writeRegister(0x4A, 0x00);
	writeRegister(0xFF, 0x00);
	writeRegister(0x7A, 0x0A);
	writeRegister(0x7B, 0x00);
	writeRegister(0x78, 0x21);
	writeRegister(0xFF, 0x01);
	writeRegister(0x23, 0x34);
	writeRegister(0x42, 0x00);
	writeRegister(0x44, 0xFF);
	writeRegister(0x45, 0x26);
	writeRegister(0x46, 0x05);
	writeRegister(0x40, 0x40);
	writeRegister(0x0E, 0x06);
	writeRegister(0x20, 0x1A);
	writeRegister(0x43, 0x40);
	writeRegister(0xFF, 0x00);
	writeRegister(0x34, 0x03);
	writeRegister(0x35, 0x44);
	writeRegister(0xFF, 0x01);
	writeRegister(0x31, 0x04);
	writeRegister(0x4B, 0x09);
	writeRegister(0x4C, 0x05);
	writeRegister(0x4D, 0x04);
	writeRegister(0xFF, 0x00);
	writeRegister(0x44, 0x00);
	writeRegister(0x45, 0x20);
	writeRegister(0x47, 0x08);
	writeRegister(0x48, 0x28);
	writeRegister(0x67, 0x00);
	writeRegister(0x70, 0x04);
	writeRegister(0x71, 0x01);
	writeRegister(0x72, 0xFE);
	writeRegister(0x76, 0x00);
	writeRegister(0x77, 0x00);
	writeRegister(0xFF, 0x01);
	writeRegister(0x0D, 0x01);
	writeRegister(0xFF, 0x00);
	writeRegister(0x80, 0x01);
	writeRegister(0x01, 0xF8);
	writeRegister(0xFF, 0x01);
	writeRegister(0x8E, 0x01);
	writeRegister(0x00, 0x01);
	writeRegister(0xFF, 0x00);
	writeRegister(0x80, 0x00);

	return OK;
}


bool
VL53LXX::singleRefCalibration(uint8_t byte)
{
	uint8_t val;

	writeRegister(SYSRANGE_START_REG, byte | 0x01); 		// VL53L0X_REG_SYSRANGE_MODE_START_STOP

	do {
		readRegister(RESULT_INTERRUPT_STATUS_REG, val);
	} while ((val & 0x07) == 0);

	writeRegister(SYSTEM_INTERRUPT_CLEAR_REG, 0x01);
	writeRegister(SYSRANGE_START_REG, 0x00);

	return OK;
}



/**
 * Local functions in support of the shell command.
 */
namespace vl53lxx
{

VL53LXX	*g_dev;

int 	start(uint8_t rotation);
int 	start_bus(uint8_t rotation, int i2c_bus);
int 	stop();
int 	test();
int 	info();

/**
 *
 * Attempt to start driver on all available I2C busses.
 *
 * This function will return as soon as the first sensor
 * is detected on one of the available busses or if no
 * sensors are detected.
 *
 */
int
start(uint8_t rotation)
{
	if (g_dev != nullptr) {
		PX4_ERR("already started");
		return PX4_ERROR;
	}

	for (unsigned i = 0; i < NUM_I2C_BUS_OPTIONS; i++) {
		if (start_bus(rotation, i2c_bus_options[i]) == PX4_OK) {
			return PX4_OK;
		}
	}

	return PX4_ERROR;
}

/**
 * Start the driver on a specific bus.
 *
 * This function only returns if the sensor is up and running
 * or could not be detected successfully.
 */
int
start_bus(uint8_t rotation, int i2c_bus)
{
	int fd = -1;

	if (g_dev != nullptr) {
		PX4_ERR("already started");
		return PX4_ERROR;
	}

	/* create the driver */
	g_dev = new VL53LXX(rotation, 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 = px4_open(VL53LXX_DEVICE_PATH, O_RDONLY);

	if (fd < 0) {
		goto fail;
	}

	if (ioctl(fd, SENSORIOCSPOLLRATE, SENSOR_POLLRATE_DEFAULT) < 0) {
		goto fail;
	}

	px4_close(fd);
	return PX4_OK;

fail:

	if (fd >= 0) {
		px4_close(fd);
	}

	if (g_dev != nullptr) {
		delete g_dev;
		g_dev = nullptr;
	}

	return PX4_ERROR;
}

/**
 * Stop the driver
 */
int
stop()
{
	if (g_dev != nullptr) {
		delete g_dev;
		g_dev = nullptr;

	} else {
		PX4_ERR("driver not running");
		return PX4_ERROR;
	}

	return PX4_OK;
}

/**
 * Perform some basic functional tests on the driver;
 * make sure we can collect data from the sensor in polled
 * and automatic modes.
 */
int
test()
{
	struct distance_sensor_s report;
	ssize_t sz;

	int fd = px4_open(VL53LXX_DEVICE_PATH, O_RDONLY);

	if (fd < 0) {
		PX4_ERR("%s open failed (try 'vl53lxx start' if the driver is not running)", VL53LXX_DEVICE_PATH);
		return PX4_ERROR;
	}

	/* do a simple demand read */
	sz = read(fd, &report, sizeof(report));

	if (sz != sizeof(report)) {
		PX4_ERR("immediate read failed");
		return PX4_ERROR;
	}

	print_message(report);

	px4_close(fd);

	PX4_INFO("PASS");
	return PX4_OK;
}


/**
 * Print a little info about the driver.
 */
int
info()
{
	if (g_dev == nullptr) {
		PX4_ERR("driver not running");
		return PX4_ERROR;
	}

	printf("state @ %p\n", g_dev);
	g_dev->print_info();

	return PX4_OK;
}

} // namespace vl53lxx


static void
vl53lxx_usage()
{
	PX4_INFO("usage: vl53lxx command [options]");
	PX4_INFO("options:");
	PX4_INFO("\t-b --bus i2cbus (%d)", VL53LXX_BUS_DEFAULT);
	PX4_INFO("\t-a --all");
	PX4_INFO("\t-R --rotation (%d)", distance_sensor_s::ROTATION_DOWNWARD_FACING);
	PX4_INFO("command:");
	PX4_INFO("\tstart|stop|test|info");
}


int
vl53lxx_main(int argc, char *argv[])
{
	int ch;
	int myoptind = 1;
	const char *myoptarg = nullptr;
	uint8_t rotation = distance_sensor_s::ROTATION_DOWNWARD_FACING;
	bool start_all = false;

	int i2c_bus = VL53LXX_BUS_DEFAULT;

	while ((ch = px4_getopt(argc, argv, "ab:R:", &myoptind, &myoptarg)) != EOF) {
		switch (ch) {
		case 'R':
			rotation = (uint8_t)atoi(myoptarg);
			break;

		case 'b':
			i2c_bus = atoi(myoptarg);
			break;

		case 'a':
			start_all = true;
			break;

		default:
			PX4_WARN("Unknown option!");
			goto out_error;
		}
	}

	/*
	 * Start/load the driver.
	 */
	if (!strcmp(argv[myoptind], "start")) {
		if (start_all) {
			return vl53lxx::start(rotation);

		} else {
			return vl53lxx::start_bus(rotation, i2c_bus);
		}
	}

	/*
	 * Stop the driver
	 */
	if (!strcmp(argv[myoptind], "stop")) {
		return vl53lxx::stop();
	}

	/*
	 * Test the driver/device.
	 */
	if (!strcmp(argv[myoptind], "test")) {
		return vl53lxx::test();
	}

	/*
	 * Print driver information.
	 */
	if (!strcmp(argv[myoptind], "info") || !strcmp(argv[myoptind], "status")) {
		return vl53lxx::info();
	}

out_error:

	vl53lxx_usage();
	return PX4_ERROR;
}