| Elantech Touchpad Driver |
| ======================== |
| |
| Copyright (C) 2007-2008 Arjan Opmeer <arjan@opmeer.net> |
| |
| Extra information for hardware version 1 found and |
| provided by Steve Havelka |
| |
| Version 2 (EeePC) hardware support based on patches |
| received from Woody at Xandros and forwarded to me |
| by user StewieGriffin at the eeeuser.com forum |
| |
| |
| Contents |
| ~~~~~~~~ |
| |
| 1. Introduction |
| 2. Extra knobs |
| 3. Differentiating hardware versions |
| 4. Hardware version 1 |
| 4.1 Registers |
| 4.2 Native relative mode 4 byte packet format |
| 4.3 Native absolute mode 4 byte packet format |
| 5. Hardware version 2 |
| 5.1 Registers |
| 5.2 Native absolute mode 6 byte packet format |
| 5.2.1 Parity checking and packet re-synchronization |
| 5.2.2 One/Three finger touch |
| 5.2.3 Two finger touch |
| 6. Hardware version 3 |
| 6.1 Registers |
| 6.2 Native absolute mode 6 byte packet format |
| 6.2.1 One/Three finger touch |
| 6.2.2 Two finger touch |
| 7. Hardware version 4 |
| 7.1 Registers |
| 7.2 Native absolute mode 6 byte packet format |
| 7.2.1 Status packet |
| 7.2.2 Head packet |
| 7.2.3 Motion packet |
| |
| |
| |
| 1. Introduction |
| ~~~~~~~~~~~~ |
| |
| Currently the Linux Elantech touchpad driver is aware of two different |
| hardware versions unimaginatively called version 1 and version 2. Version 1 |
| is found in "older" laptops and uses 4 bytes per packet. Version 2 seems to |
| be introduced with the EeePC and uses 6 bytes per packet, and provides |
| additional features such as position of two fingers, and width of the touch. |
| |
| The driver tries to support both hardware versions and should be compatible |
| with the Xorg Synaptics touchpad driver and its graphical configuration |
| utilities. |
| |
| Additionally the operation of the touchpad can be altered by adjusting the |
| contents of some of its internal registers. These registers are represented |
| by the driver as sysfs entries under /sys/bus/serio/drivers/psmouse/serio? |
| that can be read from and written to. |
| |
| Currently only the registers for hardware version 1 are somewhat understood. |
| Hardware version 2 seems to use some of the same registers but it is not |
| known whether the bits in the registers represent the same thing or might |
| have changed their meaning. |
| |
| On top of that, some register settings have effect only when the touchpad is |
| in relative mode and not in absolute mode. As the Linux Elantech touchpad |
| driver always puts the hardware into absolute mode not all information |
| mentioned below can be used immediately. But because there is no freely |
| available Elantech documentation the information is provided here anyway for |
| completeness sake. |
| |
| |
| ///////////////////////////////////////////////////////////////////////////// |
| |
| |
| 2. Extra knobs |
| ~~~~~~~~~~~ |
| |
| Currently the Linux Elantech touchpad driver provides two extra knobs under |
| /sys/bus/serio/drivers/psmouse/serio? for the user. |
| |
| * debug |
| |
| Turn different levels of debugging ON or OFF. |
| |
| By echoing "0" to this file all debugging will be turned OFF. |
| |
| Currently a value of "1" will turn on some basic debugging and a value of |
| "2" will turn on packet debugging. For hardware version 1 the default is |
| OFF. For version 2 the default is "1". |
| |
| Turning packet debugging on will make the driver dump every packet |
| received to the syslog before processing it. Be warned that this can |
| generate quite a lot of data! |
| |
| * paritycheck |
| |
| Turns parity checking ON or OFF. |
| |
| By echoing "0" to this file parity checking will be turned OFF. Any |
| non-zero value will turn it ON. For hardware version 1 the default is ON. |
| For version 2 the default it is OFF. |
| |
| Hardware version 1 provides basic data integrity verification by |
| calculating a parity bit for the last 3 bytes of each packet. The driver |
| can check these bits and reject any packet that appears corrupted. Using |
| this knob you can bypass that check. |
| |
| Hardware version 2 does not provide the same parity bits. Only some basic |
| data consistency checking can be done. For now checking is disabled by |
| default. Currently even turning it on will do nothing. |
| |
| ///////////////////////////////////////////////////////////////////////////// |
| |
| 3. Differentiating hardware versions |
| ================================= |
| |
| To detect the hardware version, read the version number as param[0].param[1].param[2] |
| |
| 4 bytes version: (after the arrow is the name given in the Dell-provided driver) |
| 02.00.22 => EF013 |
| 02.06.00 => EF019 |
| In the wild, there appear to be more versions, such as 00.01.64, 01.00.21, |
| 02.00.00, 02.00.04, 02.00.06. |
| |
| 6 bytes: |
| 02.00.30 => EF113 |
| 02.08.00 => EF023 |
| 02.08.XX => EF123 |
| 02.0B.00 => EF215 |
| 04.01.XX => Scroll_EF051 |
| 04.02.XX => EF051 |
| In the wild, there appear to be more versions, such as 04.03.01, 04.04.11. There |
| appears to be almost no difference, except for EF113, which does not report |
| pressure/width and has different data consistency checks. |
| |
| Probably all the versions with param[0] <= 01 can be considered as |
| 4 bytes/firmware 1. The versions < 02.08.00, with the exception of 02.00.30, as |
| 4 bytes/firmware 2. Everything >= 02.08.00 can be considered as 6 bytes. |
| |
| ///////////////////////////////////////////////////////////////////////////// |
| |
| 4. Hardware version 1 |
| ================== |
| |
| 4.1 Registers |
| ~~~~~~~~~ |
| |
| By echoing a hexadecimal value to a register it contents can be altered. |
| |
| For example: |
| |
| echo -n 0x16 > reg_10 |
| |
| * reg_10 |
| |
| bit 7 6 5 4 3 2 1 0 |
| B C T D L A S E |
| |
| E: 1 = enable smart edges unconditionally |
| S: 1 = enable smart edges only when dragging |
| A: 1 = absolute mode (needs 4 byte packets, see reg_11) |
| L: 1 = enable drag lock (see reg_22) |
| D: 1 = disable dynamic resolution |
| T: 1 = disable tapping |
| C: 1 = enable corner tap |
| B: 1 = swap left and right button |
| |
| * reg_11 |
| |
| bit 7 6 5 4 3 2 1 0 |
| 1 0 0 H V 1 F P |
| |
| P: 1 = enable parity checking for relative mode |
| F: 1 = enable native 4 byte packet mode |
| V: 1 = enable vertical scroll area |
| H: 1 = enable horizontal scroll area |
| |
| * reg_20 |
| |
| single finger width? |
| |
| * reg_21 |
| |
| scroll area width (small: 0x40 ... wide: 0xff) |
| |
| * reg_22 |
| |
| drag lock time out (short: 0x14 ... long: 0xfe; |
| 0xff = tap again to release) |
| |
| * reg_23 |
| |
| tap make timeout? |
| |
| * reg_24 |
| |
| tap release timeout? |
| |
| * reg_25 |
| |
| smart edge cursor speed (0x02 = slow, 0x03 = medium, 0x04 = fast) |
| |
| * reg_26 |
| |
| smart edge activation area width? |
| |
| |
| 4.2 Native relative mode 4 byte packet format |
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
| |
| byte 0: |
| bit 7 6 5 4 3 2 1 0 |
| c c p2 p1 1 M R L |
| |
| L, R, M = 1 when Left, Right, Middle mouse button pressed |
| some models have M as byte 3 odd parity bit |
| when parity checking is enabled (reg_11, P = 1): |
| p1..p2 = byte 1 and 2 odd parity bit |
| c = 1 when corner tap detected |
| |
| byte 1: |
| bit 7 6 5 4 3 2 1 0 |
| dx7 dx6 dx5 dx4 dx3 dx2 dx1 dx0 |
| |
| dx7..dx0 = x movement; positive = right, negative = left |
| byte 1 = 0xf0 when corner tap detected |
| |
| byte 2: |
| bit 7 6 5 4 3 2 1 0 |
| dy7 dy6 dy5 dy4 dy3 dy2 dy1 dy0 |
| |
| dy7..dy0 = y movement; positive = up, negative = down |
| |
| byte 3: |
| parity checking enabled (reg_11, P = 1): |
| |
| bit 7 6 5 4 3 2 1 0 |
| w h n1 n0 ds3 ds2 ds1 ds0 |
| |
| normally: |
| ds3..ds0 = scroll wheel amount and direction |
| positive = down or left |
| negative = up or right |
| when corner tap detected: |
| ds0 = 1 when top right corner tapped |
| ds1 = 1 when bottom right corner tapped |
| ds2 = 1 when bottom left corner tapped |
| ds3 = 1 when top left corner tapped |
| n1..n0 = number of fingers on touchpad |
| only models with firmware 2.x report this, models with |
| firmware 1.x seem to map one, two and three finger taps |
| directly to L, M and R mouse buttons |
| h = 1 when horizontal scroll action |
| w = 1 when wide finger touch? |
| |
| otherwise (reg_11, P = 0): |
| |
| bit 7 6 5 4 3 2 1 0 |
| ds7 ds6 ds5 ds4 ds3 ds2 ds1 ds0 |
| |
| ds7..ds0 = vertical scroll amount and direction |
| negative = up |
| positive = down |
| |
| |
| 4.3 Native absolute mode 4 byte packet format |
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
| |
| EF013 and EF019 have a special behaviour (due to a bug in the firmware?), and |
| when 1 finger is touching, the first 2 position reports must be discarded. |
| This counting is reset whenever a different number of fingers is reported. |
| |
| byte 0: |
| firmware version 1.x: |
| |
| bit 7 6 5 4 3 2 1 0 |
| D U p1 p2 1 p3 R L |
| |
| L, R = 1 when Left, Right mouse button pressed |
| p1..p3 = byte 1..3 odd parity bit |
| D, U = 1 when rocker switch pressed Up, Down |
| |
| firmware version 2.x: |
| |
| bit 7 6 5 4 3 2 1 0 |
| n1 n0 p2 p1 1 p3 R L |
| |
| L, R = 1 when Left, Right mouse button pressed |
| p1..p3 = byte 1..3 odd parity bit |
| n1..n0 = number of fingers on touchpad |
| |
| byte 1: |
| firmware version 1.x: |
| |
| bit 7 6 5 4 3 2 1 0 |
| f 0 th tw x9 x8 y9 y8 |
| |
| tw = 1 when two finger touch |
| th = 1 when three finger touch |
| f = 1 when finger touch |
| |
| firmware version 2.x: |
| |
| bit 7 6 5 4 3 2 1 0 |
| . . . . x9 x8 y9 y8 |
| |
| byte 2: |
| bit 7 6 5 4 3 2 1 0 |
| x7 x6 x5 x4 x3 x2 x1 x0 |
| |
| x9..x0 = absolute x value (horizontal) |
| |
| byte 3: |
| bit 7 6 5 4 3 2 1 0 |
| y7 y6 y5 y4 y3 y2 y1 y0 |
| |
| y9..y0 = absolute y value (vertical) |
| |
| |
| ///////////////////////////////////////////////////////////////////////////// |
| |
| |
| 5. Hardware version 2 |
| ================== |
| |
| |
| 5.1 Registers |
| ~~~~~~~~~ |
| |
| By echoing a hexadecimal value to a register it contents can be altered. |
| |
| For example: |
| |
| echo -n 0x56 > reg_10 |
| |
| * reg_10 |
| |
| bit 7 6 5 4 3 2 1 0 |
| 0 1 0 1 0 1 D 0 |
| |
| D: 1 = enable drag and drop |
| |
| * reg_11 |
| |
| bit 7 6 5 4 3 2 1 0 |
| 1 0 0 0 S 0 1 0 |
| |
| S: 1 = enable vertical scroll |
| |
| * reg_21 |
| |
| unknown (0x00) |
| |
| * reg_22 |
| |
| drag and drop release time out (short: 0x70 ... long 0x7e; |
| 0x7f = never i.e. tap again to release) |
| |
| |
| 5.2 Native absolute mode 6 byte packet format |
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
| 5.2.1 Parity checking and packet re-synchronization |
| There is no parity checking, however some consistency checks can be performed. |
| |
| For instance for EF113: |
| SA1= packet[0]; |
| A1 = packet[1]; |
| B1 = packet[2]; |
| SB1= packet[3]; |
| C1 = packet[4]; |
| D1 = packet[5]; |
| if( (((SA1 & 0x3C) != 0x3C) && ((SA1 & 0xC0) != 0x80)) || // check Byte 1 |
| (((SA1 & 0x0C) != 0x0C) && ((SA1 & 0xC0) == 0x80)) || // check Byte 1 (one finger pressed) |
| (((SA1 & 0xC0) != 0x80) && (( A1 & 0xF0) != 0x00)) || // check Byte 2 |
| (((SB1 & 0x3E) != 0x38) && ((SA1 & 0xC0) != 0x80)) || // check Byte 4 |
| (((SB1 & 0x0E) != 0x08) && ((SA1 & 0xC0) == 0x80)) || // check Byte 4 (one finger pressed) |
| (((SA1 & 0xC0) != 0x80) && (( C1 & 0xF0) != 0x00)) ) // check Byte 5 |
| // error detected |
| |
| For all the other ones, there are just a few constant bits: |
| if( ((packet[0] & 0x0C) != 0x04) || |
| ((packet[3] & 0x0f) != 0x02) ) |
| // error detected |
| |
| |
| In case an error is detected, all the packets are shifted by one (and packet[0] is discarded). |
| |
| 5.2.2 One/Three finger touch |
| ~~~~~~~~~~~~~~~~ |
| |
| byte 0: |
| |
| bit 7 6 5 4 3 2 1 0 |
| n1 n0 w3 w2 . . R L |
| |
| L, R = 1 when Left, Right mouse button pressed |
| n1..n0 = number of fingers on touchpad |
| |
| byte 1: |
| |
| bit 7 6 5 4 3 2 1 0 |
| p7 p6 p5 p4 x11 x10 x9 x8 |
| |
| byte 2: |
| |
| bit 7 6 5 4 3 2 1 0 |
| x7 x6 x5 x4 x3 x2 x1 x0 |
| |
| x11..x0 = absolute x value (horizontal) |
| |
| byte 3: |
| |
| bit 7 6 5 4 3 2 1 0 |
| n4 vf w1 w0 . . . b2 |
| |
| n4 = set if more than 3 fingers (only in 3 fingers mode) |
| vf = a kind of flag ? (only on EF123, 0 when finger is over one |
| of the buttons, 1 otherwise) |
| w3..w0 = width of the finger touch (not EF113) |
| b2 (on EF113 only, 0 otherwise), b2.R.L indicates one button pressed: |
| 0 = none |
| 1 = Left |
| 2 = Right |
| 3 = Middle (Left and Right) |
| 4 = Forward |
| 5 = Back |
| 6 = Another one |
| 7 = Another one |
| |
| byte 4: |
| |
| bit 7 6 5 4 3 2 1 0 |
| p3 p1 p2 p0 y11 y10 y9 y8 |
| |
| p7..p0 = pressure (not EF113) |
| |
| byte 5: |
| |
| bit 7 6 5 4 3 2 1 0 |
| y7 y6 y5 y4 y3 y2 y1 y0 |
| |
| y11..y0 = absolute y value (vertical) |
| |
| |
| 5.2.3 Two finger touch |
| ~~~~~~~~~~~~~~~~ |
| |
| Note that the two pairs of coordinates are not exactly the coordinates of the |
| two fingers, but only the pair of the lower-left and upper-right coordinates. |
| So the actual fingers might be situated on the other diagonal of the square |
| defined by these two points. |
| |
| byte 0: |
| |
| bit 7 6 5 4 3 2 1 0 |
| n1 n0 ay8 ax8 . . R L |
| |
| L, R = 1 when Left, Right mouse button pressed |
| n1..n0 = number of fingers on touchpad |
| |
| byte 1: |
| |
| bit 7 6 5 4 3 2 1 0 |
| ax7 ax6 ax5 ax4 ax3 ax2 ax1 ax0 |
| |
| ax8..ax0 = lower-left finger absolute x value |
| |
| byte 2: |
| |
| bit 7 6 5 4 3 2 1 0 |
| ay7 ay6 ay5 ay4 ay3 ay2 ay1 ay0 |
| |
| ay8..ay0 = lower-left finger absolute y value |
| |
| byte 3: |
| |
| bit 7 6 5 4 3 2 1 0 |
| . . by8 bx8 . . . . |
| |
| byte 4: |
| |
| bit 7 6 5 4 3 2 1 0 |
| bx7 bx6 bx5 bx4 bx3 bx2 bx1 bx0 |
| |
| bx8..bx0 = upper-right finger absolute x value |
| |
| byte 5: |
| |
| bit 7 6 5 4 3 2 1 0 |
| by7 by8 by5 by4 by3 by2 by1 by0 |
| |
| by8..by0 = upper-right finger absolute y value |
| |
| ///////////////////////////////////////////////////////////////////////////// |
| |
| 6. Hardware version 3 |
| ================== |
| |
| 6.1 Registers |
| ~~~~~~~~~ |
| * reg_10 |
| |
| bit 7 6 5 4 3 2 1 0 |
| 0 0 0 0 R F T A |
| |
| A: 1 = enable absolute tracking |
| T: 1 = enable two finger mode auto correct |
| F: 1 = disable ABS Position Filter |
| R: 1 = enable real hardware resolution |
| |
| 6.2 Native absolute mode 6 byte packet format |
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
| 1 and 3 finger touch shares the same 6-byte packet format, except that |
| 3 finger touch only reports the position of the center of all three fingers. |
| |
| Firmware would send 12 bytes of data for 2 finger touch. |
| |
| Note on debounce: |
| In case the box has unstable power supply or other electricity issues, or |
| when number of finger changes, F/W would send "debounce packet" to inform |
| driver that the hardware is in debounce status. |
| The debouce packet has the following signature: |
| byte 0: 0xc4 |
| byte 1: 0xff |
| byte 2: 0xff |
| byte 3: 0x02 |
| byte 4: 0xff |
| byte 5: 0xff |
| When we encounter this kind of packet, we just ignore it. |
| |
| 6.2.1 One/Three finger touch |
| ~~~~~~~~~~~~~~~~~~~~~~ |
| |
| byte 0: |
| |
| bit 7 6 5 4 3 2 1 0 |
| n1 n0 w3 w2 0 1 R L |
| |
| L, R = 1 when Left, Right mouse button pressed |
| n1..n0 = number of fingers on touchpad |
| |
| byte 1: |
| |
| bit 7 6 5 4 3 2 1 0 |
| p7 p6 p5 p4 x11 x10 x9 x8 |
| |
| byte 2: |
| |
| bit 7 6 5 4 3 2 1 0 |
| x7 x6 x5 x4 x3 x2 x1 x0 |
| |
| x11..x0 = absolute x value (horizontal) |
| |
| byte 3: |
| |
| bit 7 6 5 4 3 2 1 0 |
| 0 0 w1 w0 0 0 1 0 |
| |
| w3..w0 = width of the finger touch |
| |
| byte 4: |
| |
| bit 7 6 5 4 3 2 1 0 |
| p3 p1 p2 p0 y11 y10 y9 y8 |
| |
| p7..p0 = pressure |
| |
| byte 5: |
| |
| bit 7 6 5 4 3 2 1 0 |
| y7 y6 y5 y4 y3 y2 y1 y0 |
| |
| y11..y0 = absolute y value (vertical) |
| |
| 6.2.2 Two finger touch |
| ~~~~~~~~~~~~~~~~ |
| |
| The packet format is exactly the same for two finger touch, except the hardware |
| sends two 6 byte packets. The first packet contains data for the first finger, |
| the second packet has data for the second finger. So for two finger touch a |
| total of 12 bytes are sent. |
| |
| ///////////////////////////////////////////////////////////////////////////// |
| |
| 7. Hardware version 4 |
| ================== |
| |
| 7.1 Registers |
| ~~~~~~~~~ |
| * reg_07 |
| |
| bit 7 6 5 4 3 2 1 0 |
| 0 0 0 0 0 0 0 A |
| |
| A: 1 = enable absolute tracking |
| |
| 7.2 Native absolute mode 6 byte packet format |
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
| v4 hardware is a true multitouch touchpad, capable of tracking up to 5 fingers. |
| Unfortunately, due to PS/2's limited bandwidth, its packet format is rather |
| complex. |
| |
| Whenever the numbers or identities of the fingers changes, the hardware sends a |
| status packet to indicate how many and which fingers is on touchpad, followed by |
| head packets or motion packets. A head packet contains data of finger id, finger |
| position (absolute x, y values), width, and pressure. A motion packet contains |
| two fingers' position delta. |
| |
| For example, when status packet tells there are 2 fingers on touchpad, then we |
| can expect two following head packets. If the finger status doesn't change, |
| the following packets would be motion packets, only sending delta of finger |
| position, until we receive a status packet. |
| |
| One exception is one finger touch. when a status packet tells us there is only |
| one finger, the hardware would just send head packets afterwards. |
| |
| 7.2.1 Status packet |
| ~~~~~~~~~~~~~ |
| |
| byte 0: |
| |
| bit 7 6 5 4 3 2 1 0 |
| . . . . 0 1 R L |
| |
| L, R = 1 when Left, Right mouse button pressed |
| |
| byte 1: |
| |
| bit 7 6 5 4 3 2 1 0 |
| . . . ft4 ft3 ft2 ft1 ft0 |
| |
| ft4 ft3 ft2 ft1 ft0 ftn = 1 when finger n is on touchpad |
| |
| byte 2: not used |
| |
| byte 3: |
| |
| bit 7 6 5 4 3 2 1 0 |
| . . . 1 0 0 0 0 |
| |
| constant bits |
| |
| byte 4: |
| |
| bit 7 6 5 4 3 2 1 0 |
| p . . . . . . . |
| |
| p = 1 for palm |
| |
| byte 5: not used |
| |
| 7.2.2 Head packet |
| ~~~~~~~~~~~ |
| |
| byte 0: |
| |
| bit 7 6 5 4 3 2 1 0 |
| w3 w2 w1 w0 0 1 R L |
| |
| L, R = 1 when Left, Right mouse button pressed |
| w3..w0 = finger width (spans how many trace lines) |
| |
| byte 1: |
| |
| bit 7 6 5 4 3 2 1 0 |
| p7 p6 p5 p4 x11 x10 x9 x8 |
| |
| byte 2: |
| |
| bit 7 6 5 4 3 2 1 0 |
| x7 x6 x5 x4 x3 x2 x1 x0 |
| |
| x11..x0 = absolute x value (horizontal) |
| |
| byte 3: |
| |
| bit 7 6 5 4 3 2 1 0 |
| id2 id1 id0 1 0 0 0 1 |
| |
| id2..id0 = finger id |
| |
| byte 4: |
| |
| bit 7 6 5 4 3 2 1 0 |
| p3 p1 p2 p0 y11 y10 y9 y8 |
| |
| p7..p0 = pressure |
| |
| byte 5: |
| |
| bit 7 6 5 4 3 2 1 0 |
| y7 y6 y5 y4 y3 y2 y1 y0 |
| |
| y11..y0 = absolute y value (vertical) |
| |
| 7.2.3 Motion packet |
| ~~~~~~~~~~~~~ |
| |
| byte 0: |
| |
| bit 7 6 5 4 3 2 1 0 |
| id2 id1 id0 w 0 1 R L |
| |
| L, R = 1 when Left, Right mouse button pressed |
| id2..id0 = finger id |
| w = 1 when delta overflows (> 127 or < -128), in this case |
| firmware sends us (delta x / 5) and (delta y / 5) |
| |
| byte 1: |
| |
| bit 7 6 5 4 3 2 1 0 |
| x7 x6 x5 x4 x3 x2 x1 x0 |
| |
| x7..x0 = delta x (two's complement) |
| |
| byte 2: |
| |
| bit 7 6 5 4 3 2 1 0 |
| y7 y6 y5 y4 y3 y2 y1 y0 |
| |
| y7..y0 = delta y (two's complement) |
| |
| byte 3: |
| |
| bit 7 6 5 4 3 2 1 0 |
| id2 id1 id0 1 0 0 1 0 |
| |
| id2..id0 = finger id |
| |
| byte 4: |
| |
| bit 7 6 5 4 3 2 1 0 |
| x7 x6 x5 x4 x3 x2 x1 x0 |
| |
| x7..x0 = delta x (two's complement) |
| |
| byte 5: |
| |
| bit 7 6 5 4 3 2 1 0 |
| y7 y6 y5 y4 y3 y2 y1 y0 |
| |
| y7..y0 = delta y (two's complement) |
| |
| byte 0 ~ 2 for one finger |
| byte 3 ~ 5 for another |
