Keyscan Interface Queue

Defines the keyscan interface. More...

Defines the keyscan interface.

The keyscan interface is practically defined as a queue from the consumer's perspective. Key up/down events are seen as a stream coming from the driver. In addition the interface provides the user with the ability to reset the HW as well as turn keyscaning on/off.

Up/down flag

enum
{
    KEY_DOWN = 0x0,
    KEY_UP   = 0x1
};

Special event codes used internally by the driver

enum
{
    /// Rollover event generated by the keyscan driver in case of an error (ghost or overflow)
    ROLLOVER = 0xff,

    /// Event returned to indicate the end of a scan cycle.
    END_OF_SCAN_CYCLE = 0xfe
};

Definition of a key event.

#pragma pack(1)
typedef PACKED struct
{
    /// Key code. This is the location in the keyscan matrix that is pressed/released.
    /// May be implemented as ((row * numCols) + col) or ((col * numRows) + row.
    BYTE keyCode;

    /// Reserved bits
    BYTE reserved : 6;

    /// Up/down flag
    BYTE upDownFlag : 1;

    /// Should be toggled for every scan cycle in which a new event is queued.
    /// Use of this flag is optional. If used, it allows the consumer to determine whether
    /// an event is detected in the same scan cycle as the previous event or a different one.
    /// Note that this flag does not indicate any separation in time.
    BYTE scanCycleFlag : 1;
}KeyEvent;
#pragma pack()