Driver for the Linear Tech LTC4150 Coulomb Counter (a.k.a. More...

Detailed Description

Driver for the Linear Tech LTC4150 Coulomb Counter (a.k.a.

battery gauge sensor or power consumption sensor)

Wiring the LTC4150

Hint: M Grusin thankfully created an open hardware breakout board. As a result, virtually all LTC4150 breakout boards are using this schematic. Whenever this documentation refers to a breakout board, this open hardware board is meant. Of course, this driver works with the "bare" LTC4150 as well.

Please note that this driver works interrupt driven and does not clear the signal. Thus, the /CLR and /INT pins on the LTC4150 need to be connected (in case of the breakout board: close solder jumper SJ1), so that the signal is automatically cleared.

Hint: The breakout board uses external pull up resistors on /INT, POL and /SHDN. Therefore /SHDN can be left unconnected and no internal pull ups are required for /INT and POL. In case your board uses 3.3V logic the solder jumpers SJ2 and SJ3 have to be closed, in case of 5V they have to remain open. Connect the VIO pin to the logic level, GND to ground, IN+ and IN- to the power supply and use OUT+ and OUT- to power your board.

In the easiest case only the /INT pin needs to be connected to a GPIO, and (in case of external pull ups) /SHDN and POL can be left unconnected. The GPIO /INT is connected to support for interrupts, /SHDN and POL (if connected) do not require interrupt support.

In case a battery is used the POL pin connected to another GPIO. This allows to distinguish between charge drawn from the battery and charge transferred into the battery (used to load it).

In case support to power off the LTC4150 is desired, the /SHDN pin needs to be connected to a third GPIO.

Things to keep in mind

The LTC4150 creates pulses with a frequency depending on the current drawn. Thus, more interrupts need to be handled when more current is drawn, which in turn increases system load (and power consumption). The interrupt service routing is quite short and even when used outside of specification less than 20 ticks per second will occur. Hence, this effect should hopefully be negligible.

Files
file	ltc4150.h
	LTC4150 coulomb counter.

file	ltc4150_params.h
	Default configuration for LTC4150 coulomb counters.

Data Structures
struct	ltc4150_recorder_t
	Interface to allow recording of the drawn current in a user defined resolution. More...

struct	ltc4150_params_t
	Parameters required to set up the LTC4150 coulomb counter. More...

struct	ltc4150_dev
	LTC4150 coulomb counter. More...

struct	ltc4150_last_minute_data_t
	Data structure used by ltc4150_last_minute. More...

Typedefs
typedef struct ltc4150_dev	ltc4150_dev_t
	LTC4150 coulomb counter.

Enumerations
enum	{ LTC4150_INT_EXT_PULL_UP = 0x01 , LTC4150_POL_EXT_PULL_UP = 0x02 , LTC4150_EXT_PULL_UP = LTC4150_INT_EXT_PULL_UP \| LTC4150_POL_EXT_PULL_UP }
	Configuration flags of the LTC4150 coulomb counter. More...

enum	ltc4150_dir_t { LTC4150_CHARGE , LTC4150_DISCHARGE }
	Enumeration of directions in which the charge can be transferred. More...

Functions
int	ltc4150_init (ltc4150_dev_t dev, const ltc4150_params_t params)
	Initialize the LTC4150 driver.

int	ltc4150_reset_counters (ltc4150_dev_t *dev)
	Clear current counters of the given LTC4150 device.

int	ltc4150_shutdown (ltc4150_dev_t *dev)
	Disable the interrupt handler and turn the chip off.

int	ltc4150_charge (ltc4150_dev_t dev, uint32_t charged, uint32_t *discharged)
	Get the measured charge since boot or last reset in millicoulomb.

int	ltc4150_avg_current (ltc4150_dev_t dev, int16_t dest)
	Get the average current drawn in E-01 milliampere.

int	ltc4150_last_minute_charge (ltc4150_dev_t dev, ltc4150_last_minute_data_t data, uint32_t charged, uint32_t discharged)
	Get the measured charge in the last minute.

void	ltc4150_pulses2c (const ltc4150_dev_t dev, uint32_t charged, uint32_t *discharged, uint32_t raw_charged, uint32_t raw_discharged)
	Convert the raw data (# pulses) acquired by the LTC4150 device to charge information in millicoulomb.

Variables
const ltc4150_recorder_t	ltc4150_last_minute
	Records the charge transferred within the last minute using.

Typedef Documentation

◆ ltc4150_dev_t

typedef struct ltc4150_dev ltc4150_dev_t

LTC4150 coulomb counter.

Definition at line 103 of file ltc4150.h.

Enumeration Type Documentation

◆ anonymous enum

anonymous enum

Configuration flags of the LTC4150 coulomb counter.

Enumerator
LTC4150_INT_EXT_PULL_UP	External pull on the /INT pin is present.
LTC4150_POL_EXT_PULL_UP	External pull on the /POL pin is present.
LTC4150_EXT_PULL_UP	External pull on the /INT and the /POL pin is present.

Definition at line 77 of file ltc4150.h.

◆ ltc4150_dir_t

enum ltc4150_dir_t

Enumeration of directions in which the charge can be transferred.

Enumerator
LTC4150_CHARGE	The battery is charged.
LTC4150_DISCHARGE	Charge is drawn from the battery.

Definition at line 95 of file ltc4150.h.

Function Documentation

◆ ltc4150_avg_current()

int ltc4150_avg_current	(	ltc4150_dev_t *	dev,
		int16_t *	dest
	)

Get the average current drawn in E-01 milliampere.

This will return the average current drawn since boot or last reset until the last pulse from the LTC4150 was received. The value might thus be a bit outdated (0.8 seconds for the breakout board and a current of 100mA, 79 seconds for a current of 1mA).

Parameters

	dev	The LTC4150 device to read data from
[out]	dest	Store the average current drawn in E-01 milliampere here

Return values

0	Success
-EINVAL	Called with an invalid argument
-EAGAIN	Called before enough data samples have been acquired. (Wait for at least one second or one pulse from the LTC4150, whichever takes longer.)

◆ ltc4150_charge()

int ltc4150_charge	(	ltc4150_dev_t *	dev,
		uint32_t *	charged,
		uint32_t *	discharged
	)

Get the measured charge since boot or last reset in millicoulomb.

Parameters

	dev	The LTC4150 device to read data from
[out]	charged	The charge transferred in charging direction
[out]	discharged	The charge transferred in discharging direction

Return values

0	Success
-EINVAL	Called with an invalid argument

Passing NULL for charged or discharged is allowed, if only one information is of interest.

◆ ltc4150_init()

int ltc4150_init	(	ltc4150_dev_t *	dev,
		const ltc4150_params_t *	params
	)

Initialize the LTC4150 driver.

Parameters

dev	Device to initialize
params	Information on how the LTC4150 is connected

Return values

0	Success
-EINVAL	Called with invalid argument(s)
-EIO	IO failure (`gpio_init()`/`gpio_init_int()` failed)

◆ ltc4150_last_minute_charge()

int ltc4150_last_minute_charge	(	ltc4150_dev_t *	dev,
		ltc4150_last_minute_data_t *	data,
		uint32_t *	charged,
		uint32_t *	discharged
	)

Get the measured charge in the last minute.

Parameters

	dev	The LTC4150 device to read data from
	data	The data recorded by ltc4150_last_minute
[out]	charged	The charge transferred in charging direction
[out]	discharged	The charge transferred in discharging direction

Return values

0	Success
-EINVAL	Called with an invalid argument

Warning: The returned data may be outdated up to ten seconds

Passing NULL for charged or discharged is allowed, if only one information is of interest.

◆ ltc4150_pulses2c()

void ltc4150_pulses2c	(	const ltc4150_dev_t *	dev,
		uint32_t *	charged,
		uint32_t *	discharged,
		uint32_t	raw_charged,
		uint32_t	raw_discharged
	)

Convert the raw data (# pulses) acquired by the LTC4150 device to charge information in millicoulomb.

Note: This function will make writing data recorders (see ltc4150_recorder_t) easier, but is not intended for end users

Parameters

	dev	LTC4150 device the data was received from
[out]	charged	Charge in charging direction is stored here
[out]	discharged	Charge in discharging direction is stored here
[in]	raw_charged	Number of pulses in charging direction
[in]	raw_discharged	Number of pulses in discharging direction

◆ ltc4150_reset_counters()

int ltc4150_reset_counters ( ltc4150_dev_t * dev )

Clear current counters of the given LTC4150 device.

Parameters

dev	The LTC4150 device to clear current counters from

Return values

0	Success
-EINVAL	Called with an invalid argument

◆ ltc4150_shutdown()

int ltc4150_shutdown ( ltc4150_dev_t * dev )

Disable the interrupt handler and turn the chip off.

Parameters

dev	Previously initialized device to power off

Return values

0	Success
-EINVAL	Called with invalid argument(s)

The driver can be reinitialized to power on the LTC4150 chip again

Detailed Description

Wiring the LTC4150

Things to keep in mind

Files

Data Structures

Typedefs

Enumerations

Functions

Variables

Typedef Documentation

◆ ltc4150_dev_t

Enumeration Type Documentation

◆ anonymous enum

◆ ltc4150_dir_t

Function Documentation

◆ ltc4150_avg_current()

◆ ltc4150_charge()

◆ ltc4150_init()

◆ ltc4150_last_minute_charge()

◆ ltc4150_pulses2c()

◆ ltc4150_reset_counters()

◆ ltc4150_shutdown()