1ALPS Touchpad Protocol 2---------------------- 3 4Introduction 5------------ 6 7Currently the ALPS touchpad driver supports four protocol versions in use by 8ALPS touchpads, called versions 1, 2, 3, and 4. Information about the various 9protocol versions is contained in the following sections. 10 11Detection 12--------- 13 14All ALPS touchpads should respond to the "E6 report" command sequence: 15E8-E6-E6-E6-E9. An ALPS touchpad should respond with either 00-00-0A or 1600-00-64 if no buttons are pressed. The bits 0-2 of the first byte will be 1s 17if some buttons are pressed. 18 19If the E6 report is successful, the touchpad model is identified using the "E7 20report" sequence: E8-E7-E7-E7-E9. The response is the model signature and is 21matched against known models in the alps_model_data_array. 22 23With protocol versions 3 and 4, the E7 report model signature is always 2473-02-64. To differentiate between these versions, the response from the 25"Enter Command Mode" sequence must be inspected as described below. 26 27Command Mode 28------------ 29 30Protocol versions 3 and 4 have a command mode that is used to read and write 31one-byte device registers in a 16-bit address space. The command sequence 32EC-EC-EC-E9 places the device in command mode, and the device will respond 33with 88-07 followed by a third byte. This third byte can be used to determine 34whether the devices uses the version 3 or 4 protocol. 35 36To exit command mode, PSMOUSE_CMD_SETSTREAM (EA) is sent to the touchpad. 37 38While in command mode, register addresses can be set by first sending a 39specific command, either EC for v3 devices or F5 for v4 devices. Then the 40address is sent one nibble at a time, where each nibble is encoded as a 41command with optional data. This enoding differs slightly between the v3 and 42v4 protocols. 43 44Once an address has been set, the addressed register can be read by sending 45PSMOUSE_CMD_GETINFO (E9). The first two bytes of the response contains the 46address of the register being read, and the third contains the value of the 47register. Registers are written by writing the value one nibble at a time 48using the same encoding used for addresses. 49 50Packet Format 51------------- 52 53In the following tables, the following notation is used. 54 55 CAPITALS = stick, miniscules = touchpad 56 57?'s can have different meanings on different models, such as wheel rotation, 58extra buttons, stick buttons on a dualpoint, etc. 59 60PS/2 packet format 61------------------ 62 63 byte 0: 0 0 YSGN XSGN 1 M R L 64 byte 1: X7 X6 X5 X4 X3 X2 X1 X0 65 byte 2: Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0 66 67Note that the device never signals overflow condition. 68 69ALPS Absolute Mode - Protocol Verion 1 70-------------------------------------- 71 72 byte 0: 1 0 0 0 1 x9 x8 x7 73 byte 1: 0 x6 x5 x4 x3 x2 x1 x0 74 byte 2: 0 ? ? l r ? fin ges 75 byte 3: 0 ? ? ? ? y9 y8 y7 76 byte 4: 0 y6 y5 y4 y3 y2 y1 y0 77 byte 5: 0 z6 z5 z4 z3 z2 z1 z0 78 79ALPS Absolute Mode - Protocol Version 2 80--------------------------------------- 81 82 byte 0: 1 ? ? ? 1 ? ? ? 83 byte 1: 0 x6 x5 x4 x3 x2 x1 x0 84 byte 2: 0 x10 x9 x8 x7 ? fin ges 85 byte 3: 0 y9 y8 y7 1 M R L 86 byte 4: 0 y6 y5 y4 y3 y2 y1 y0 87 byte 5: 0 z6 z5 z4 z3 z2 z1 z0 88 89Dualpoint device -- interleaved packet format 90--------------------------------------------- 91 92 byte 0: 1 1 0 0 1 1 1 1 93 byte 1: 0 x6 x5 x4 x3 x2 x1 x0 94 byte 2: 0 x10 x9 x8 x7 0 fin ges 95 byte 3: 0 0 YSGN XSGN 1 1 1 1 96 byte 4: X7 X6 X5 X4 X3 X2 X1 X0 97 byte 5: Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0 98 byte 6: 0 y9 y8 y7 1 m r l 99 byte 7: 0 y6 y5 y4 y3 y2 y1 y0 100 byte 8: 0 z6 z5 z4 z3 z2 z1 z0 101 102ALPS Absolute Mode - Protocol Version 3 103--------------------------------------- 104 105ALPS protocol version 3 has three different packet formats. The first two are 106associated with touchpad events, and the third is associatd with trackstick 107events. 108 109The first type is the touchpad position packet. 110 111 byte 0: 1 ? x1 x0 1 1 1 1 112 byte 1: 0 x10 x9 x8 x7 x6 x5 x4 113 byte 2: 0 y10 y9 y8 y7 y6 y5 y4 114 byte 3: 0 M R L 1 m r l 115 byte 4: 0 mt x3 x2 y3 y2 y1 y0 116 byte 5: 0 z6 z5 z4 z3 z2 z1 z0 117 118Note that for some devices the trackstick buttons are reported in this packet, 119and on others it is reported in the trackstick packets. 120 121The second packet type contains bitmaps representing the x and y axes. In the 122bitmaps a given bit is set if there is a finger covering that position on the 123given axis. Thus the bitmap packet can be used for low-resolution multi-touch 124data, although finger tracking is not possible. This packet also encodes the 125number of contacts (f1 and f0 in the table below). 126 127 byte 0: 1 1 x1 x0 1 1 1 1 128 byte 1: 0 x8 x7 x6 x5 x4 x3 x2 129 byte 2: 0 y7 y6 y5 y4 y3 y2 y1 130 byte 3: 0 y10 y9 y8 1 1 1 1 131 byte 4: 0 x14 x13 x12 x11 x10 x9 y0 132 byte 5: 0 1 ? ? ? ? f1 f0 133 134This packet only appears after a position packet with the mt bit set, and 135usually only appears when there are two or more contacts (although 136occassionally it's seen with only a single contact). 137 138The final v3 packet type is the trackstick packet. 139 140 byte 0: 1 1 x7 y7 1 1 1 1 141 byte 1: 0 x6 x5 x4 x3 x2 x1 x0 142 byte 2: 0 y6 y5 y4 y3 y2 y1 y0 143 byte 3: 0 1 0 0 1 0 0 0 144 byte 4: 0 z4 z3 z2 z1 z0 ? ? 145 byte 5: 0 0 1 1 1 1 1 1 146 147ALPS Absolute Mode - Protocol Version 4 148--------------------------------------- 149 150Protocol version 4 has an 8-byte packet format. 151 152 byte 0: 1 ? x1 x0 1 1 1 1 153 byte 1: 0 x10 x9 x8 x7 x6 x5 x4 154 byte 2: 0 y10 y9 y8 y7 y6 y5 y4 155 byte 3: 0 1 x3 x2 y3 y2 y1 y0 156 byte 4: 0 ? ? ? 1 ? r l 157 byte 5: 0 z6 z5 z4 z3 z2 z1 z0 158 byte 6: bitmap data (described below) 159 byte 7: bitmap data (described below) 160 161The last two bytes represent a partial bitmap packet, with 3 full packets 162required to construct a complete bitmap packet. Once assembled, the 6-byte 163bitmap packet has the following format: 164 165 byte 0: 0 1 x7 x6 x5 x4 x3 x2 166 byte 1: 0 x1 x0 y4 y3 y2 y1 y0 167 byte 2: 0 0 ? x14 x13 x12 x11 x10 168 byte 3: 0 x9 x8 y9 y8 y7 y6 y5 169 byte 4: 0 0 0 0 0 0 0 0 170 byte 5: 0 0 0 0 0 0 0 y10 171 172There are several things worth noting here. 173 174 1) In the bitmap data, bit 6 of byte 0 serves as a sync byte to 175 identify the first fragment of a bitmap packet. 176 177 2) The bitmaps represent the same data as in the v3 bitmap packets, although 178 the packet layout is different. 179 180 3) There doesn't seem to be a count of the contact points anywhere in the v4 181 protocol packets. Deriving a count of contact points must be done by 182 analyzing the bitmaps. 183 184 4) There is a 3 to 1 ratio of position packets to bitmap packets. Therefore 185 MT position can only be updated for every third ST position update, and 186 the count of contact points can only be updated every third packet as 187 well. 188 189So far no v4 devices with tracksticks have been encountered. 190