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 * 1. Redistributions of source code must retain the above copyright
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/**
 * @file batt_smbus.cpp
 *
 * Driver for a battery monitor connected via SMBus (I2C).
 *
 * @author Randy Mackay <rmackay9@yahoo.com>
 */

#include <nuttx/config.h>

#include <sys/types.h>
#include <stdint.h>
#include <stdlib.h>
#include <stdbool.h>
#include <sched.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 <ctype.h>

#include <nuttx/arch.h>
#include <nuttx/wqueue.h>
#include <nuttx/clock.h>

#include <board_config.h>

#include <systemlib/perf_counter.h>
#include <systemlib/err.h>
#include <systemlib/systemlib.h>

#include <uORB/uORB.h>
#include <uORB/topics/subsystem_info.h>
#include <uORB/topics/battery_status.h>

#include <float.h>

#include <drivers/device/i2c.h>
#include <drivers/drv_hrt.h>
#include <drivers/drv_batt_smbus.h>
#include <drivers/device/ringbuffer.h>

#define BATT_SMBUS_ADDR_MIN			0x08	///< lowest possible address
#define BATT_SMBUS_ADDR_MAX			0x7F	///< highest possible address

#define BATT_SMBUS_I2C_BUS			PX4_I2C_BUS_EXPANSION
#define BATT_SMBUS_ADDR				0x0B	///< I2C address
#define BATT_SMBUS_TEMP				0x08	///< temperature register
#define BATT_SMBUS_VOLTAGE			0x09	///< voltage register
#define BATT_SMBUS_DESIGN_CAPACITY		0x18	///< design capacity register
#define BATT_SMBUS_DESIGN_VOLTAGE		0x19	///< design voltage register
#define BATT_SMBUS_SERIALNUM			0x1c	///< serial number register
#define BATT_SMBUS_MANUFACTURE_NAME		0x20	///< manufacturer name
#define BATT_SMBUS_MANUFACTURE_INFO		0x25	///< cell voltage register
#define BATT_SMBUS_CURRENT			0x2a	///< current register
#define BATT_SMBUS_MEASUREMENT_INTERVAL_MS	(1000000 / 10)	///< time in microseconds, measure at 10hz
#define BATT_SMBUS_TIMEOUT_MS		10000000	///< timeout looking for battery 10seconds after startup

#define BATT_SMBUS_PEC_POLYNOMIAL		0x07	///< Polynomial for calculating PEC

#ifndef CONFIG_SCHED_WORKQUEUE
# error This requires CONFIG_SCHED_WORKQUEUE.
#endif

class BATT_SMBUS : public device::I2C
{
public:
	BATT_SMBUS(int bus = PX4_I2C_BUS_EXPANSION, uint16_t batt_smbus_addr = BATT_SMBUS_ADDR);
	virtual ~BATT_SMBUS();

	/**
	 * Initialize device
	 *
	 * Calls probe() to check for device on bus.
	 *
	 * @return 0 on success, error code on failure
	 */
	virtual int		init();

	/**
	 * Test device
	 *
	 * @return 0 on success, error code on failure
	 */
	virtual int		test();

	/**
	 * Search all possible slave addresses for a smart battery
	 */
	int			search();

protected:
	/**
	 * Check if the device can be contacted
	 */
	virtual int		probe();

private:

	/**
	 * Start periodic reads from the battery
	 */
	void			start();

	/**
	 * Stop periodic reads from the battery
	 */
	void			stop();

	/**
	 * static function that is called by worker queue
	 */
	static void		cycle_trampoline(void *arg);

	/**
	 * perform a read from the battery
	 */
	void			cycle();

	/**
	 * Read a word from specified register
	 */
	int			read_reg(uint8_t reg, uint16_t &val);

	/**
	 * Read block from bus
	 * @return returns number of characters read if successful, zero if unsuccessful
	 */
	uint8_t			read_block(uint8_t reg, uint8_t *data, uint8_t max_len, bool append_zero);

	/**
	 * Calculate PEC for a read or write from the battery
	 * @param buff is the data that was read or will be written
	 */
	uint8_t			get_PEC(uint8_t cmd, bool reading, const uint8_t buff[], uint8_t len) const;

	// internal variables
	bool			_enabled;	///< true if we have successfully connected to battery
	work_s			_work;		///< work queue for scheduling reads
	RingBuffer		*_reports;	///< buffer of recorded voltages, currents
	struct battery_status_s _last_report;	///< last published report, used for test()
	orb_advert_t		_batt_topic;	///< uORB battery topic
	orb_id_t		_batt_orb_id;	///< uORB battery topic ID
	uint64_t		_start_time;	///< system time we first attempt to communicate with battery
};

namespace
{
BATT_SMBUS *g_batt_smbus;	///< device handle. For now, we only support one BATT_SMBUS device
}

void batt_smbus_usage();

extern "C" __EXPORT int batt_smbus_main(int argc, char *argv[]);

BATT_SMBUS::BATT_SMBUS(int bus, uint16_t batt_smbus_addr) :
	I2C("batt_smbus", BATT_SMBUS_DEVICE_PATH, bus, batt_smbus_addr, 400000),
	_enabled(false),
	_work{},
	_reports(nullptr),
	_batt_topic(-1),
	_batt_orb_id(nullptr),
	_start_time(0)
{
	// work_cancel in the dtor will explode if we don't do this...
	memset(&_work, 0, sizeof(_work));

	// capture startup time
	_start_time = hrt_absolute_time();
}

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

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

int
BATT_SMBUS::init()
{
	int ret = ENOTTY;

	// attempt to initialise I2C bus
	ret = I2C::init();

	if (ret != OK) {
		errx(1, "failed to init I2C");
		return ret;

	} else {
		// allocate basic report buffers
		_reports = new RingBuffer(2, sizeof(struct battery_status_s));

		if (_reports == nullptr) {
			ret = ENOTTY;

		} else {
			// start work queue
			start();
		}
	}

	// init orb id
	_batt_orb_id = ORB_ID(battery_status);

	return ret;
}

int
BATT_SMBUS::test()
{
	int sub = orb_subscribe(ORB_ID(battery_status));
	bool updated = false;
	struct battery_status_s status;
	uint64_t start_time = hrt_absolute_time();

	// loop for 5 seconds
	while ((hrt_absolute_time() - start_time) < 5000000) {

		// display new info that has arrived from the orb
		orb_check(sub, &updated);

		if (updated) {
			if (orb_copy(ORB_ID(battery_status), sub, &status) == OK) {
				warnx("V=%4.2f C=%4.2f", status.voltage_v, status.current_a);
			}
		}

		// sleep for 0.05 seconds
		usleep(50000);
	}

	return OK;
}

int
BATT_SMBUS::search()
{
	bool found_slave = false;
	uint16_t tmp;

	// search through all valid SMBus addresses
	for (uint8_t i = BATT_SMBUS_ADDR_MIN; i <= BATT_SMBUS_ADDR_MAX; i++) {
		set_address(i);

		if (read_reg(BATT_SMBUS_VOLTAGE, tmp) == OK) {
			warnx("battery found at 0x%x", (int)i);
			found_slave = true;
		}

		// short sleep
		usleep(1);
	}

	// display completion message
	if (found_slave) {
		warnx("Done.");

	} else {
		warnx("No smart batteries found.");
	}

	return OK;
}

int
BATT_SMBUS::probe()
{
	// always return OK to ensure device starts
	return OK;
}

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

	// schedule a cycle to start things
	work_queue(HPWORK, &_work, (worker_t)&BATT_SMBUS::cycle_trampoline, this, 1);
}

void
BATT_SMBUS::stop()
{
	work_cancel(HPWORK, &_work);
}

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

	dev->cycle();
}

void
BATT_SMBUS::cycle()
{
	// get current time
	uint64_t now = hrt_absolute_time();

	// exit without rescheduling if we have failed to find a battery after 10 seconds
	if (!_enabled && (now - _start_time > BATT_SMBUS_TIMEOUT_MS)) {
		warnx("did not find smart battery");
		return;
	}

	// read data from sensor
	struct battery_status_s new_report;

	// set time of reading
	new_report.timestamp = now;

	// read voltage
	uint16_t tmp;

	if (read_reg(BATT_SMBUS_VOLTAGE, tmp) == OK) {
		// initialise new_report
		memset(&new_report, 0, sizeof(new_report));

		// convert millivolts to volts
		new_report.voltage_v = ((float)tmp) / 1000.0f;

		// read current
		usleep(1);
		uint8_t buff[4];

		if (read_block(BATT_SMBUS_CURRENT, buff, 4, false) == 4) {
			new_report.current_a = -(float)((int32_t)((uint32_t)buff[3] << 24 | (uint32_t)buff[2] << 16 | (uint32_t)buff[1] << 8 | (uint32_t)buff[0])) / 1000.0f;
		}

		// publish to orb
		if (_batt_topic != -1) {
			orb_publish(_batt_orb_id, _batt_topic, &new_report);

		} else {
			_batt_topic = orb_advertise(_batt_orb_id, &new_report);

			if (_batt_topic < 0) {
				errx(1, "ADVERT FAIL");
			}
		}

		// copy report for test()
		_last_report = new_report;

		// post a report to the ring
		_reports->force(&new_report);

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

		// record we are working
		_enabled = true;
	}

	// schedule a fresh cycle call when the measurement is done
	work_queue(HPWORK, &_work, (worker_t)&BATT_SMBUS::cycle_trampoline, this,
		   USEC2TICK(BATT_SMBUS_MEASUREMENT_INTERVAL_MS));
}

int
BATT_SMBUS::read_reg(uint8_t reg, uint16_t &val)
{
	uint8_t buff[3];	// 2 bytes of data + PEC

	// read from register
	int ret = transfer(&reg, 1, buff, 3);

	if (ret == OK) {
		// check PEC
		uint8_t pec = get_PEC(reg, true, buff, 2);

		if (pec == buff[2]) {
			val = (uint16_t)buff[1] << 8 | (uint16_t)buff[0];

		} else {
			ret = ENOTTY;
		}
	}

	// return success or failure
	return ret;
}

uint8_t
BATT_SMBUS::read_block(uint8_t reg, uint8_t *data, uint8_t max_len, bool append_zero)
{
	uint8_t buff[max_len + 2];  // buffer to hold results

	usleep(1);

	// read bytes including PEC
	int ret = transfer(&reg, 1, buff, max_len + 2);

	// return zero on failure
	if (ret != OK) {
		return 0;
	}

	// get length
	uint8_t bufflen = buff[0];

	// sanity check length returned by smbus
	if (bufflen == 0 || bufflen > max_len) {
		return 0;
	}

	// check PEC
	uint8_t pec = get_PEC(reg, true, buff, bufflen + 1);

	if (pec != buff[bufflen + 1]) {
		// debug
		warnx("CurrPEC:%x vs MyPec:%x", (int)buff[bufflen + 1], (int)pec);
		return 0;

	}

	// copy data
	memcpy(data, &buff[1], bufflen);

	// optionally add zero to end
	if (append_zero) {
		data[bufflen] = '\0';
	}

	// return success
	return bufflen;
}

uint8_t
BATT_SMBUS::get_PEC(uint8_t cmd, bool reading, const uint8_t buff[], uint8_t len) const
{
	// exit immediately if no data
	if (len <= 0) {
		return 0;
	}

	// prepare temp buffer for calcing crc
	uint8_t tmp_buff[len + 3];
	tmp_buff[0] = (uint8_t)get_address() << 1;
	tmp_buff[1] = cmd;
	tmp_buff[2] = tmp_buff[0] | (uint8_t)reading;
	memcpy(&tmp_buff[3], buff, len);

	// initialise crc to zero
	uint8_t crc = 0;
	uint8_t shift_reg = 0;
	bool do_invert;

	// for each byte in the stream
	for (uint8_t i = 0; i < sizeof(tmp_buff); i++) {
		// load next data byte into the shift register
		shift_reg = tmp_buff[i];

		// for each bit in the current byte
		for (uint8_t j = 0; j < 8; j++) {
			do_invert = (crc ^ shift_reg) & 0x80;
			crc <<= 1;
			shift_reg <<= 1;

			if (do_invert) {
				crc ^= BATT_SMBUS_PEC_POLYNOMIAL;
			}
		}
	}

	// return result
	return crc;
}

///////////////////////// shell functions ///////////////////////

void
batt_smbus_usage()
{
	warnx("missing command: try 'start', 'test', 'stop', 'search'");
	warnx("options:");
	warnx("    -b i2cbus (%d)", BATT_SMBUS_I2C_BUS);
	warnx("    -a addr (0x%x)", BATT_SMBUS_ADDR);
}

int
batt_smbus_main(int argc, char *argv[])
{
	int i2cdevice = BATT_SMBUS_I2C_BUS;
	int batt_smbusadr = BATT_SMBUS_ADDR; // 7bit address

	int ch;

	// jump over start/off/etc and look at options first
	while ((ch = getopt(argc, argv, "a:b:")) != EOF) {
		switch (ch) {
		case 'a':
			batt_smbusadr = strtol(optarg, NULL, 0);
			break;

		case 'b':
			i2cdevice = strtol(optarg, NULL, 0);
			break;

		default:
			batt_smbus_usage();
			exit(0);
		}
	}

	if (optind >= argc) {
		batt_smbus_usage();
		exit(1);
	}

	const char *verb = argv[optind];

	if (!strcmp(verb, "start")) {
		if (g_batt_smbus != nullptr) {
			errx(1, "already started");

		} else {
			// create new global object
			g_batt_smbus = new BATT_SMBUS(i2cdevice, batt_smbusadr);

			if (g_batt_smbus == nullptr) {
				errx(1, "new failed");
			}

			if (OK != g_batt_smbus->init()) {
				delete g_batt_smbus;
				g_batt_smbus = nullptr;
				errx(1, "init failed");
			}
		}

		exit(0);
	}

	// need the driver past this point
	if (g_batt_smbus == nullptr) {
		warnx("not started");
		batt_smbus_usage();
		exit(1);
	}

	if (!strcmp(verb, "test")) {
		g_batt_smbus->test();
		exit(0);
	}

	if (!strcmp(verb, "stop")) {
		delete g_batt_smbus;
		g_batt_smbus = nullptr;
		exit(0);
	}

	if (!strcmp(verb, "search")) {
		g_batt_smbus->search();
		exit(0);
	}

	batt_smbus_usage();
	exit(0);
}