Sifteo::MotionIterator Class Reference

Utility for reading low-level motion events from a MotionBuffer. More...

#include <sifteo/motion.h>

Public Member Functions
Byte3	accel () const
	Return the acceleration sample at the iterator's current position. More...
void	adjustTicks (int32_t value)
	Add a value to the tick counter. More...
	MotionIterator (_SYSMotionBuffer *buffer)
	Construct a new MotionIterator, attached to the provided MotionBuffer. More...
bool	next ()
	Advance to the next motion sample, if possible. More...
float	seconds () const
	Return the timestamp at the iterator's current position, in seconds. More...
void	setTicks (uint32_t value)
	Modify the tick counter.
uint32_t	ticks () const
	Return the timestamp at the iterator's current position, in ticks. More...

Static Public Attributes
static const unsigned	TICK_HZ = MotionBuffer<>::TICK_HZ
	Reciprocal of the MotionBuffer's timestamp unit, in Hertz.
static const unsigned	TICK_NS = MotionBuffer<>::TICK_NS
	Duration of the MotionBuffer's timestamp unit, in nanoseconds.
static const unsigned	TICK_US = MotionBuffer<>::TICK_US
	Duration of the MotionBuffer's timestamp unit, in microseconds.

Detailed Description

Utility for reading low-level motion events from a MotionBuffer.

This object keeps track of the state necessary to extract a stream of motion events from a MotionBuffer. It manages the FIFO head pointer, and keeps track of the current time.

After it is created, the iterator has an indeterminate state. It may be advanced to the next available motion sample with next().

Constructor & Destructor Documentation

Sifteo::MotionIterator::MotionIterator ( _SYSMotionBuffer *  buffer )

inline

Construct a new MotionIterator, attached to the provided MotionBuffer.

The read pointer is initialized to be equal to the system's write pointer, meaning that next() will return false until the first new acceleration sample is collected after this iterator has been constructed.

Member Function Documentation

Byte3 Sifteo::MotionIterator::accel ( ) const

inline

Return the acceleration sample at the iterator's current position.

The units and coordinate system are identical to that of CubeID::accel().

void Sifteo::MotionIterator::adjustTicks ( int32_t  value )

inline

Add a value to the tick counter.

This helps with use cases where you'd like to use the tick counter as an accumulator for sample rate conversion. If you want to collect a sample every N ticks, for example, you can wait until ticks() is at least N, then use adjustTicks(-N) to remove that span of time from the accumulator.

bool Sifteo::MotionIterator::next ( )

inline

Advance to the next motion sample, if possible.

If another sample is available, advances to it and returns true. If no more samples are ready, returns false.

float Sifteo::MotionIterator::seconds ( ) const

inline

Return the timestamp at the iterator's current position, in seconds.

This is like ticks(), except we scale the result to seconds, and return it as a floating point number. Note that this has less precision than ticks(), and there is no good way to handle roll-over, so it should only be used if you know you won't be sampling data for a very long period of time.

uint32_t Sifteo::MotionIterator::ticks ( ) const

inline

Return the timestamp at the iterator's current position, in ticks.

This timestamp starts out at zero, and increases at each call to next(). It is a 32-bit counter, in units of ticks as described by TICK_NS, TICK_US, and TICK_HZ.

This timestamp counter will roll over after approximately 12 days.

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The documentation for this class was generated from the following file:

• motion.h