Touch filters

Within the mtouch section, start a subsection with begin filter and end it with end filter to specify a filter. For example:

begin mtouch
    driver = focaltech
    options = generic_j6=1,interrupt=1002,i2c_slave_addr=0x38,
              i2c_devname=/dev/i2c0,protocol_ver=2

    begin filter
...    type
...    options
    end filter
end mtouch

Touch filter parameters

Touch filters provide a method of removing unwanted coordinates or coordinate-noise, depending on the filter type that you use. Some filters adjust the coordinate data or suppress them depending on the purpose of the filter. These are the touch filter parameters that are available:


Parameter	Description	Type	Possible value(s)
type	The series of filters that are applied to the touch coordinates.	String	`ballistic` Minimizes the noise normally seen on successive touch events that follow a low-speed ballistic trajectory. The lower the speed of the ballistic movement (e.g., a stationary finger), the more gain reduction is applied to the speed of the movement. By doing so, the result is a solid touch with no noise. `compression` Compresses the number of events sent to Screen. Duplicate events are removed and events within the specified threshold are compressed. `edge_swipe_detect` Detects the passing of a finger over the edge of the touch surface. This lets you get swipe gestures starting from outside the screen. `kalman` Minimizes the tracking noise of a moving finger on a given touch surface by use of the Kalman filter algorithm.
options	Filter-specific options. The available filter options depend on the filter type. The format for configuring the filter options is: options = `filter_option`=`value` where `filter_option` is one of the options listed under "Touch Filter options" and `value` is its associated value that you want to set it to. If there are multiple options to specify, then separate each option-value pair by a comma: options = `filter_option1`=`value`,`filter_option2`=`value`	String	Based on your filter type, see below for the valid filter options.

Touch Filter options

Valid filter options for configuration depend on the filter type. See below for the filter options that are acceptable in the options parameter for the mtouch_filter section (begin mtouch_filter).

Ballistic filter (e.g., type = ballistic)


Filter option	Description	Default
`scale`	FP scale factor	256
`min_gain`	Minimal gain	8
`low_speed`	Low speed threshold	32

Compression filter (e.g., type = compression)


Filter option	Description	Default
`threshold`	Threshold is the maximum distance a coordinate can drift, from its starting point, before an event is sent	10
`min_event_interval`	Minimum event interval in microseconds	-1
`num_coords_to_average`	Number of event coordinates to average	0

Edge-swipe filter (e.g., type = edge_swipe_detect)

These are the options for filter order:


Filter option	Description	Default
`filter_order`	Filter Order	2

These are the options for left edge (e.g., when the x touch coordinate is 0):


Filter option	Description	Default
`xl_enable`	Apply detection	1
`xl_bezel`	Bezel width	50
`xl_speed`	Speed threshold	25
`xl_jitter`	Jitter control	0
`xl_reject_physical_bezel`	Reject physical bezel	0

These are the options for right edge (e.g., when the x touch coordinate is at the maximum possible value):


Filter option	Description	Default
`xh_enable`	Apply detection	1
`xh_bezel`	Bezel width	50
`xh_speed`	Speed threshold	25
`xh_jitter`	Jitter control	0
`xh_reject_physical_bezel`	Reject physical bezel	0

These are the options for the top edge (e.g., when the y touch coordinate is 0):


Filter option	Description	Default
`yl_enable`	Apply detection	1
`yl_bezel`	Bezel width	80
`yl_speed`	Speed threshold	25
`yl_jitter`	Jitter control	0
`yl_reject_physical_bezel`	Reject physical bezel	0

These are the options for the bottom edge (e.g., when the y touch coordinate is at the maximum possible value):


Filter option	Description	Default
`yh_enable`	Apply detection	1
`yh_bezel`	Bezel width	50
`yh_speed`	Speed threshold	25
`yh_jitter`	Jitter control	0
`yh_reject_physical_bezel`	Reject physical bezel	0

Note:

The edge-swipe filter options nomenclature is:

xl: x-low border, near x=0;
xh: x-high border, near x=maximal X touch coordinate;
yl: y-low border, near y=0;
yh: y-high border, near y=maximal Y touch coordinate;

Kalman filter (e.g., type = kalman)

These are the options for Noise variance:


Filter option	Description	Default
`proc_noise_x_var`	Process noise variance (X)	32
`proc_noise_y_var`	Process noise variance (Y)	32
`meas_noise_x_var`	Measurement noise variance(X)	100
`meas_noise_y_var`	Measurement noise variance (Y)	100

These are the options for adaptive speed threshold:


Filter option	Description	Default
`slot_threshold_1`	Adaptive speed threshold 1	30
`slot_threshold_2`	Adaptive speed threshold 2	20
`slot_threshold_3`	Adaptive speed threshold 3	10
`slot_threshold_4`	Adaptive speed threshold 4	5