Configuration parameters for filter

The following are valid parameters that can be configured under the filter section:

Parameter Description Type Possible Value(s)
type The series of filters that are applied to the touch coordinates. integer
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.
Detects the passing of a finger over the edge of the touch surface. This lets you get swipe gestures starting from outside the screen.
Minimizes the tracking noise of a moving finger on a given touch surface by use of the Kalman filter algorithm.

Filter specific options. The available filter options depend on the filter type. The format for configuring filter options is: options= <filter option>=<value> or, if there are multiple options to specify, then each option-value pair will be separated by a comma: options= <filter option1>=<value>,<filter option2>=<value>


Options are listed below per filter type:

  • ballistic
    Filter option Description Default
    scale FP scale factor 256
    min_gain Minimal gain 8
    low_speed Low speed threshold 32
  • edge_swipe_detect
    Table 1. Filter order
    Filter option Description Default
    filter_order Filter Order 2
    Table 2. Left edge (x=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
    Table 3. Right edge (x=max(raw_x))
    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
    Table 4. Top edge (y=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
    Table 5. Bottom edge (y=max(raw_y))
    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: edge-swipe filter options nomenclature:
    • 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
    Table 6. 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
    Table 7. Adaptive speed threshnold
    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
  • bezel_touch
    Filter option Description Default
    parrallel_threshold Filter parallel threshold 140
    perpendicular_threshold Filter perpendicular threshold 70