Compass

Magnetometer-based compass heading. More...

Enumerations
enum	MagCalStatus { MagCalStatusNoSolution , MagCalStatusSavedSampleMatch , MagCalStatusNewSolutionAvail , MagCalStatusNewLockedSolutionAvail }
	Result of feeding a sample to the hard iron calibration. More...

Functions
void	ecompass_service_init (void)
	Register the compass with the event service.
void	ecompass_service_handle (void)
	Process a new magnetometer sample.
void	ecompass_handle_battery_state_change_event (PreciseBatteryChargeState new_state)
	Handle a battery state change.
MagCalStatus	ecomp_corr_add_raw_mag_sample (int16_t *sample, int16_t *saved_corr, int16_t *new_corr)
	Feed a raw magnetometer sample to the hard iron calibration.
void	ecomp_corr_reset (void)
	Drop the samples collected by ecomp_corr_add_raw_mag_sample() and reset its state.
bool	sys_ecompass_service_subscribed (void)
	Check whether the current task is subscribed to the compass.
void	sys_ecompass_get_last_heading (CompassHeadingData *data)
	Get the last published heading.

Detailed Description

Magnetometer-based compass heading.

While a process subscribes to PEBBLE_COMPASS_DATA_EVENT, the magnetometer and accelerometer are sampled and a tilt-compensated magnetic heading is published with each event. Hard iron correction is calibrated on the fly, first at a higher sampling rate for a few minutes; calibration is suspended while the charger is plugged in and restarted once unplugged. The heading types shared with the app SDK (CompassHeading, CompassStatus, CompassHeadingData) are documented in the SDK.

Enumeration Type Documentation

MagCalStatus

enum MagCalStatus

Result of feeding a sample to the hard iron calibration.

Enumerator
MagCalStatusNoSolution	No new correction estimate available.
MagCalStatusSavedSampleMatch	Several fits close to the saved correction were found.
MagCalStatusNewSolutionAvail	A new correction estimate is available.
MagCalStatusNewLockedSolutionAvail	Several fits close to one another were found; the correction is their average.

Function Documentation

ecomp_corr_add_raw_mag_sample()

MagCalStatus ecomp_corr_add_raw_mag_sample ( int16_t *  sample, int16_t *  saved_corr, int16_t *  new_corr  )

extern

Feed a raw magnetometer sample to the hard iron calibration.

Selects well-spread points among the samples and fits a sphere to them; its origin is the hard iron correction.

Parameters

	sample	Raw sample, 3 axes.
	saved_corr	Previously saved correction, 3 axes, or NULL if none.
[out]	new_corr	Correction found, 3 axes; valid unless MagCalStatusNoSolution is returned.

Returns

Calibration status.

ecomp_corr_reset()

void ecomp_corr_reset ( void  )

extern

Drop the samples collected by ecomp_corr_add_raw_mag_sample() and reset its state.

ecompass_handle_battery_state_change_event()

void ecompass_handle_battery_state_change_event ( PreciseBatteryChargeState  new_state )

extern

Handle a battery state change.

Plugging the charger invalidates the calibration; unplugging it restarts calibration.

Parameters

new_state

New battery state.

ecompass_service_handle()

void ecompass_service_handle ( void  )

extern

Process a new magnetometer sample.

Called from KernelMain when the magnetometer has data. Updates the calibration and posts a PEBBLE_COMPASS_DATA_EVENT with the new heading.

ecompass_service_init()

void ecompass_service_init ( void  )

extern

Register the compass with the event service.

sys_ecompass_get_last_heading()

void sys_ecompass_get_last_heading

(

CompassHeadingData *

data

)

Get the last published heading.

Parameters

[out]

data

Heading and calibration status.

sys_ecompass_service_subscribed()

bool sys_ecompass_service_subscribed

(

void

)

Check whether the current task is subscribed to the compass.

Returns

true if subscribed.