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Diffstat (limited to 'doc/devel/PenButtons.txt')
| -rw-r--r-- | doc/devel/PenButtons.txt | 218 |
1 files changed, 218 insertions, 0 deletions
diff --git a/doc/devel/PenButtons.txt b/doc/devel/PenButtons.txt new file mode 100644 index 0000000..ee35c21 --- /dev/null +++ b/doc/devel/PenButtons.txt @@ -0,0 +1,218 @@ +---------------------------------------------- +xf86-input-tc1kpen Pen Button events resolving +---------------------------------------------- + +As the implemented algorithm for button 3 emulaton +is quite complex (in meaning of compression of +semantics), I shall describe its derivation, here. +The HW mode is quite straightforward and doesn't +require closer explanation as well as the 3-button +extension to the following algorithm, I guess. + + + +Emulating button 3 with pen tap while pen button pressed +-------------------------------------------------------- + +From now on, I shall use term button for both the pen tip +and pen button (they are both buttons in terms of functionality). + + +First, what happens upon a button press/release: + +1/ If a button is pressed, 2 packets are sent to the serial + device: + + i) STATUS bit set, BUTTON bit clear + ii) STATUS bit clear, BUTTON bit set + +2/ From that moment, the BUTTON bit stays set until the + button is released. Then, 2 packets are sent. The first + of those may differ regarding current state of the other + button: + + i) STATUS bit set, BUTTON bit clear if the other btn is released + BUTTON bit set if the other btn is pressed + ii) STATUS bit clear, BUTTON bit clear + +The following image describes that: + + PRESS RELEASE + V V + PACKET #: i i+1 j-1 j j+1 + -------------------------------------~---------------------------------- + + 1 +------+ +------+ + | | | | + STAT bit: 0 -----+ +----------> ---+-----+ +------+------> + + -------------------------------------~---------------------------------- + + Other btn. not pressed: + + 1 +------+---> ---+-----+ + | | + BTN bit: 0 -----+------+ +------+------+------> + + -------------------------------------~---------------------------------- + + Other btn. pressed: + + + 1 +------+---> ---+-----+------+ + | | + BTN bit: 0 -----+------+ +------+------> + + -------------------------------------~---------------------------------- + + + +Now, assuming that we watch the STATUS bit changes, +this leads to the following algorithm: + + +-------------------+ + | STATUS bit change | + +---------+---------+ + | + | + V + TRUE +-------------------+ FALSE + +----------+ STATUS bit set +-------+ + | +-------------------+ | + | | + | | + V V + FALSE +---------------+ TRUE +---------------+ FALSE + X<--------+ button > 0 | +---------+ button > 0 +----+ + +-------+-------+ | +---------------+ | + | TRUE | | + | | | + V V V + TRUE +----------------+ +----------------+ T F +----------------+ + X<-------+ btn 1 bit set | | btn 1 bit set +--->X<---+ btn 1 bit set | + +--------+-------+ +--------+-------+ +--------+-------+ + | FALSE | FALSE | TRUE + | | | + +--------------------+ V + | TRUE +----------------+ + | +-----------+ btn 2 bit set | + V | +--------+-------+ + +--------------------+ | | FALSE + | Release(button); | V V + | button = 0; | +-------------+ +----------------+ + +----------+---------+ | button = 3; | | button = 1; | + | +--------+----+ +--------+-------+ + | | | + V +--------------------+ + X | + V + +-----------------+ + | Press(button); | + +--------+--------+ + | + V + X + + ('X' points mean exit). + +The algorithm is obviously far from being efficient. +Minimalization follows: + +The original algorithm in table form: +=============+==============+=============+=============+==================== + STATUS bit | button > 0 | btn 1 bit | btn 2 bit | result +=============+==============+=============+=============+==================== + 0 | FALSE | 0 | 0 | +-------------+--------------+-------------+-------------+ + 0 | FALSE | 0 | 1 | +-------------+--------------+-------------+-------------+-------------------- + 0 | FALSE | 1 | 0 | Press(1) +-------------+--------------+-------------+-------------+-------------------- + 0 | FALSE | 1 | 1 | Press(3) +=============+==============+=============+=============+==================== + 0 | TRUE | 0 | 0 | +-------------+--------------+-------------+-------------+ Release(button); + 0 | TRUE | 0 | 1 | +-------------+--------------+-------------+-------------+-------------------- + 0 | TRUE | 1 | 0 | +-------------+--------------+-------------+-------------+ + 0 | TRUE | 1 | 1 | +=============+==============+=============+=============+==================== + 1 | FALSE | 0 | 0 | +-------------+--------------+-------------+-------------+ + 1 | FALSE | 0 | 1 | +-------------+--------------+-------------+-------------+ + 1 | FALSE | 1 | 0 | +-------------+--------------+-------------+-------------+ + 1 | FALSE | 1 | 1 | +=============+==============+=============+=============+==================== + 1 | TRUE | 0 | 0 | +-------------+--------------+-------------+-------------+ Release(button); + 1 | TRUE | 0 | 1 | +-------------+--------------+-------------+-------------+-------------------- + 1 | TRUE | 1 | 0 | +-------------+--------------+-------------+-------------+ + 1 | TRUE | 1 | 1 | +=============+==============+=============+=============+==================== + + + +Minimized table: + +=============+==============+=============+=============+==================== + STATUS bit | button > 0 | btn 1 bit | btn 2 bit | result +=============+==============+=============+=============+==================== + 0 | FALSE | 1 | 0 | Press(1); +-------------+--------------+-------------+-------------+-------------------- + 0 | FALSE | 1 | 1 | Press(3); +=============+==============+=============+=============+==================== + ? | TRUE | 0 | ? | Release(button); +=============+==============+=============+=============+==================== + ? | TRUE | 1 | ? | +-------------+--------------+-------------+-------------+ + 1 | FALSE | ? | ? | +-------------+--------------+-------------+-------------+ + 0 | FALSE | 0 | ? | +=============+==============+=============+=============+==================== + + +The minimized table may be effectively represented +by the following algorithm: + + + +-------------------+ + | STATUS bit change | + +---------+---------+ + | + | + V + FALSE +--------------------------------+ + X<---------+ button XOR btn 1 bit set | + +---------------+----------------+ + | TRUE + | + V + TRUE +---------------+ FALSE + +-------------+ button > 0 +--------------+ + | +---------------+ | + | | + V V + +-----------------------+ TRUE +-------------------+ + | Release(button); | X<---------+ STATUS bit set | + | button = 0; | +---------+---------+ + +---------+-------------+ | FALSE + | | + V V + X +--------------------------------------+ + | button = (btn 1 bit) | (btn 2 bit); | + | Press(button); | + +--------------------+-----------------+ + | + V + X + + Note that the btn bits can be used like this ^^^ because they are in fact + 2^0 and 2^1, so the bit OR equals to 1 (btn 1 bit set, btn 2 bit clear) + or 3 (btn 1 bit set, btn 2 bit set). + This was also conveniently used in the implementation. + |