Rangefinder

Functions for using the IR rangefinders. More...

Defines
#define	IR1   6
	IR Rangefinder 1.
#define	IR2   5
	IR Rangefinder 2.
#define	IR3   4
	IR Rangefinder 3.
#define	IR4   3
	IR Rangefinder 4.
#define	IR5   2
	IR Rangefinder 5.
#define	MIN_IR_ADC8   27
	smallest meaningful rangefinder reading (logarithmic scale)
#define	MAX_IR_ADC8   98
	largest meaningful rangefinder reading (logarithmic scale)
#define	MIN_IR_LINEAR   78
	smallest meaningful rangefinder reading (linear scale)
#define	MAX_IR_LINEAR   327
	largest meaningful rangefinder reading (linear scale)
Functions
void	range_init (void)
	Initialize the rangefinders.
void	range_init_filter (int filter)
	Initialize the rangefinders with option to use filtering.
int	range_read_distance (int range_id)
	Read the distance from a rangefinder.
int	linearize_distance (int value)
	Convert logarithmic-scale distance readings to a linear scale.
void	butter_init (void)
	Initialize the butterworth filter.
void	butter_task (void)
	Task that reads rangefinders and sends the values to the filter.
int	get_range_index (int range_id)
void	butter_filter (int range_id, int val)
int	range_read_filtered_distance (int range_id)
	Returns the most recent filtered reading of the rangefinder.
void	butter_filter (int range_id, int16_t val)
	Puts a raw rangefinder value through the Butterworth filter.

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Detailed Description

Functions for using the IR rangefinders.

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Function Documentation

void butter_filter	(	int	range_id,
		int	val
	)

Puts the given value from the given rangefinder through the Butterworth filter. This function should be called every time a new value is read from a rangefinder.

The Butterworth filter has a cutoff frequency of 5Hz and an order of 3

Parameters:

	range_id	the rangefinder to use. This should be one of the constants IR1 - IR5.
	the	value read from that rangefinder

Definition at line 258 of file rangefinder.c.

References MAX_IR_LINEAR, and MIN_IR_LINEAR.

void butter_init

(

void

)

Initialize the butterworth filter.

Initializes the butterworth filter.

int linearize_distance

(

int

value

)

Convert logarithmic-scale distance readings to a linear scale.

Transforms distance readings from logarithmic to linear scale. This probably isn't the function you are looking for.

Note: pgm_read_word() needs additional testing

Parameters:

value

the 8-bit analog value from rangefinder

Returns:

linearized distance reading from rangefinder (integer in [101,800])

void range_init

(

void

)

Initialize the rangefinders.

Initializes the rangefinders. This must be called before range_read_distance. This function does not initialize the filter.

See also:

range_read_distance

void range_init_filter

(

int

filter

)

Initialize the rangefinders with option to use filtering.

Initializes the rangefinders with an option to enable the Butterworth filtering.

As of 5/12/2010, the filter should only be used if you really know what you are doing. It was designed to be used with a task scheduler, which is not currently complete. This implementation uses the RTC and runs massive computations in the RTC interrupt.

Parameters:

filter

1 to enable the filter, 0 to leave it turned off

int range_read_distance

(

int

range_id

)

Read the distance from a rangefinder.

Reads the distance measured by one of the rangefinders. This distance is in arbitrary units.

Parameters:

range_id

the rangefinder to use. This should be one of the constants IR1 - IR5.

Returns:

the distance measured by the rangefinder

See also:

range_init

int range_read_filtered_distance

(

int

range_id

)

Returns the most recent filtered reading of the rangefinder.

Returns the most recent filtered reading of the rangefinder. The raw rangefinder values have been run through a Butterworth filter.

If the filter was not initialized in rangefinder_init, will return the unfiltered value from the rangefinder.

Parameters:

range_id

the rangefinder to use. This should be one of the constants IR1 - IR5.