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| 1 | +ALPS Touchpad Protocol |
| 2 | +---------------------- |
| 3 | + |
| 4 | +Introduction |
| 5 | +------------ |
| 6 | + |
| 7 | +Currently the ALPS touchpad driver supports four protocol versions in use by |
| 8 | +ALPS touchpads, called versions 1, 2, 3, and 4. Information about the various |
| 9 | +protocol versions is contained in the following sections. |
| 10 | + |
| 11 | +Detection |
| 12 | +--------- |
| 13 | + |
| 14 | +All ALPS touchpads should respond to the "E6 report" command sequence: |
| 15 | +E8-E6-E6-E6-E9. An ALPS touchpad should respond with either 00-00-0A or |
| 16 | +00-00-64. |
| 17 | + |
| 18 | +If the E6 report is successful, the touchpad model is identified using the "E7 |
| 19 | +report" sequence: E8-E7-E7-E7-E9. The response is the model signature and is |
| 20 | +matched against known models in the alps_model_data_array. |
| 21 | + |
| 22 | +With protocol versions 3 and 4, the E7 report model signature is always |
| 23 | +73-02-64. To differentiate between these versions, the response from the |
| 24 | +"Enter Command Mode" sequence must be inspected as described below. |
| 25 | + |
| 26 | +Command Mode |
| 27 | +------------ |
| 28 | + |
| 29 | +Protocol versions 3 and 4 have a command mode that is used to read and write |
| 30 | +one-byte device registers in a 16-bit address space. The command sequence |
| 31 | +EC-EC-EC-E9 places the device in command mode, and the device will respond |
| 32 | +with 88-07 followed by a third byte. This third byte can be used to determine |
| 33 | +whether the devices uses the version 3 or 4 protocol. |
| 34 | + |
| 35 | +To exit command mode, PSMOUSE_CMD_SETSTREAM (EA) is sent to the touchpad. |
| 36 | + |
| 37 | +While in command mode, register addresses can be set by first sending a |
| 38 | +specific command, either EC for v3 devices or F5 for v4 devices. Then the |
| 39 | +address is sent one nibble at a time, where each nibble is encoded as a |
| 40 | +command with optional data. This enoding differs slightly between the v3 and |
| 41 | +v4 protocols. |
| 42 | + |
| 43 | +Once an address has been set, the addressed register can be read by sending |
| 44 | +PSMOUSE_CMD_GETINFO (E9). The first two bytes of the response contains the |
| 45 | +address of the register being read, and the third contains the value of the |
| 46 | +register. Registers are written by writing the value one nibble at a time |
| 47 | +using the same encoding used for addresses. |
| 48 | + |
| 49 | +Packet Format |
| 50 | +------------- |
| 51 | + |
| 52 | +In the following tables, the following notation is used. |
| 53 | + |
| 54 | + CAPITALS = stick, miniscules = touchpad |
| 55 | + |
| 56 | +?'s can have different meanings on different models, such as wheel rotation, |
| 57 | +extra buttons, stick buttons on a dualpoint, etc. |
| 58 | + |
| 59 | +PS/2 packet format |
| 60 | +------------------ |
| 61 | + |
| 62 | + byte 0: 0 0 YSGN XSGN 1 M R L |
| 63 | + byte 1: X7 X6 X5 X4 X3 X2 X1 X0 |
| 64 | + byte 2: Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0 |
| 65 | + |
| 66 | +Note that the device never signals overflow condition. |
| 67 | + |
| 68 | +ALPS Absolute Mode - Protocol Verion 1 |
| 69 | +-------------------------------------- |
| 70 | + |
| 71 | + byte 0: 1 0 0 0 1 x9 x8 x7 |
| 72 | + byte 1: 0 x6 x5 x4 x3 x2 x1 x0 |
| 73 | + byte 2: 0 ? ? l r ? fin ges |
| 74 | + byte 3: 0 ? ? ? ? y9 y8 y7 |
| 75 | + byte 4: 0 y6 y5 y4 y3 y2 y1 y0 |
| 76 | + byte 5: 0 z6 z5 z4 z3 z2 z1 z0 |
| 77 | + |
| 78 | +ALPS Absolute Mode - Protocol Version 2 |
| 79 | +--------------------------------------- |
| 80 | + |
| 81 | + byte 0: 1 ? ? ? 1 ? ? ? |
| 82 | + byte 1: 0 x6 x5 x4 x3 x2 x1 x0 |
| 83 | + byte 2: 0 x10 x9 x8 x7 ? fin ges |
| 84 | + byte 3: 0 y9 y8 y7 1 M R L |
| 85 | + byte 4: 0 y6 y5 y4 y3 y2 y1 y0 |
| 86 | + byte 5: 0 z6 z5 z4 z3 z2 z1 z0 |
| 87 | + |
| 88 | +Dualpoint device -- interleaved packet format |
| 89 | +--------------------------------------------- |
| 90 | + |
| 91 | + byte 0: 1 1 0 0 1 1 1 1 |
| 92 | + byte 1: 0 x6 x5 x4 x3 x2 x1 x0 |
| 93 | + byte 2: 0 x10 x9 x8 x7 0 fin ges |
| 94 | + byte 3: 0 0 YSGN XSGN 1 1 1 1 |
| 95 | + byte 4: X7 X6 X5 X4 X3 X2 X1 X0 |
| 96 | + byte 5: Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0 |
| 97 | + byte 6: 0 y9 y8 y7 1 m r l |
| 98 | + byte 7: 0 y6 y5 y4 y3 y2 y1 y0 |
| 99 | + byte 8: 0 z6 z5 z4 z3 z2 z1 z0 |
| 100 | + |
| 101 | +ALPS Absolute Mode - Protocol Version 3 |
| 102 | +--------------------------------------- |
| 103 | + |
| 104 | +ALPS protocol version 3 has three different packet formats. The first two are |
| 105 | +associated with touchpad events, and the third is associatd with trackstick |
| 106 | +events. |
| 107 | + |
| 108 | +The first type is the touchpad position packet. |
| 109 | + |
| 110 | + byte 0: 1 ? x1 x0 1 1 1 1 |
| 111 | + byte 1: 0 x10 x9 x8 x7 x6 x5 x4 |
| 112 | + byte 2: 0 y10 y9 y8 y7 y6 y5 y4 |
| 113 | + byte 3: 0 M R L 1 m r l |
| 114 | + byte 4: 0 mt x3 x2 y3 y2 y1 y0 |
| 115 | + byte 5: 0 z6 z5 z4 z3 z2 z1 z0 |
| 116 | + |
| 117 | +Note that for some devices the trackstick buttons are reported in this packet, |
| 118 | +and on others it is reported in the trackstick packets. |
| 119 | + |
| 120 | +The second packet type contains bitmaps representing the x and y axes. In the |
| 121 | +bitmaps a given bit is set if there is a finger covering that position on the |
| 122 | +given axis. Thus the bitmap packet can be used for low-resolution multi-touch |
| 123 | +data, although finger tracking is not possible. This packet also encodes the |
| 124 | +number of contacts (f1 and f0 in the table below). |
| 125 | + |
| 126 | + byte 0: 1 1 x1 x0 1 1 1 1 |
| 127 | + byte 1: 0 x8 x7 x6 x5 x4 x3 x2 |
| 128 | + byte 2: 0 y7 y6 y5 y4 y3 y2 y1 |
| 129 | + byte 3: 0 y10 y9 y8 1 1 1 1 |
| 130 | + byte 4: 0 x14 x13 x12 x11 x10 x9 y0 |
| 131 | + byte 5: 0 1 ? ? ? ? f1 f0 |
| 132 | + |
| 133 | +This packet only appears after a position packet with the mt bit set, and |
| 134 | +ususally only appears when there are two or more contacts (although |
| 135 | +ocassionally it's seen with only a single contact). |
| 136 | + |
| 137 | +The final v3 packet type is the trackstick packet. |
| 138 | + |
| 139 | + byte 0: 1 1 x7 y7 1 1 1 1 |
| 140 | + byte 1: 0 x6 x5 x4 x3 x2 x1 x0 |
| 141 | + byte 2: 0 y6 y5 y4 y3 y2 y1 y0 |
| 142 | + byte 3: 0 1 0 0 1 0 0 0 |
| 143 | + byte 4: 0 z4 z3 z2 z1 z0 ? ? |
| 144 | + byte 5: 0 0 1 1 1 1 1 1 |
| 145 | + |
| 146 | +ALPS Absolute Mode - Protocol Version 4 |
| 147 | +--------------------------------------- |
| 148 | + |
| 149 | +Protocol version 4 has an 8-byte packet format. |
| 150 | + |
| 151 | + byte 0: 1 ? x1 x0 1 1 1 1 |
| 152 | + byte 1: 0 x10 x9 x8 x7 x6 x5 x4 |
| 153 | + byte 2: 0 y10 y9 y8 y7 y6 y5 y4 |
| 154 | + byte 3: 0 1 x3 x2 y3 y2 y1 y0 |
| 155 | + byte 4: 0 ? ? ? 1 ? r l |
| 156 | + byte 5: 0 z6 z5 z4 z3 z2 z1 z0 |
| 157 | + byte 6: bitmap data (described below) |
| 158 | + byte 7: bitmap data (described below) |
| 159 | + |
| 160 | +The last two bytes represent a partial bitmap packet, with 3 full packets |
| 161 | +required to construct a complete bitmap packet. Once assembled, the 6-byte |
| 162 | +bitmap packet has the following format: |
| 163 | + |
| 164 | + byte 0: 0 1 x7 x6 x5 x4 x3 x2 |
| 165 | + byte 1: 0 x1 x0 y4 y3 y2 y1 y0 |
| 166 | + byte 2: 0 0 ? x14 x13 x12 x11 x10 |
| 167 | + byte 3: 0 x9 x8 y9 y8 y7 y6 y5 |
| 168 | + byte 4: 0 0 0 0 0 0 0 0 |
| 169 | + byte 5: 0 0 0 0 0 0 0 y10 |
| 170 | + |
| 171 | +There are several things worth noting here. |
| 172 | + |
| 173 | + 1) In the bitmap data, bit 6 of byte 0 serves as a sync byte to |
| 174 | + identify the first fragment of a bitmap packet. |
| 175 | + |
| 176 | + 2) The bitmaps represent the same data as in the v3 bitmap packets, although |
| 177 | + the packet layout is different. |
| 178 | + |
| 179 | + 3) There doesn't seem to be a count of the contact points anywhere in the v4 |
| 180 | + protocol packets. Deriving a count of contact points must be done by |
| 181 | + analyzing the bitmaps. |
| 182 | + |
| 183 | + 4) There is a 3 to 1 ratio of position packets to bitmap packets. Therefore |
| 184 | + MT position can only be updated for every third ST position update, and |
| 185 | + the count of contact points can only be updated every third packet as |
| 186 | + well. |
| 187 | + |
| 188 | +So far no v4 devices with tracksticks have been encountered. |
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