1ALPS Touchpad Protocol 2---------------------- 3 4Introduction 5------------ 6Currently the ALPS touchpad driver supports five protocol versions in use by 7ALPS touchpads, called versions 1, 2, 3, 4 and 5. 8 9Since roughly mid-2010 several new ALPS touchpads have been released and 10integrated into a variety of laptops and netbooks. These new touchpads 11have enough behavior differences that the alps_model_data definition 12table, describing the properties of the different versions, is no longer 13adequate. The design choices were to re-define the alps_model_data 14table, with the risk of regression testing existing devices, or isolate 15the new devices outside of the alps_model_data table. The latter design 16choice was made. The new touchpad signatures are named: "Rushmore", 17"Pinnacle", and "Dolphin", which you will see in the alps.c code. 18For the purposes of this document, this group of ALPS touchpads will 19generically be called "new ALPS touchpads". 20 21We experimented with probing the ACPI interface _HID (Hardware ID)/_CID 22(Compatibility ID) definition as a way to uniquely identify the 23different ALPS variants but there did not appear to be a 1:1 mapping. 24In fact, it appeared to be an m:n mapping between the _HID and actual 25hardware type. 26 27Detection 28--------- 29 30All ALPS touchpads should respond to the "E6 report" command sequence: 31E8-E6-E6-E6-E9. An ALPS touchpad should respond with either 00-00-0A or 3200-00-64 if no buttons are pressed. The bits 0-2 of the first byte will be 1s 33if some buttons are pressed. 34 35If the E6 report is successful, the touchpad model is identified using the "E7 36report" sequence: E8-E7-E7-E7-E9. The response is the model signature and is 37matched against known models in the alps_model_data_array. 38 39For older touchpads supporting protocol versions 3 and 4, the E7 report 40model signature is always 73-02-64. To differentiate between these 41versions, the response from the "Enter Command Mode" sequence must be 42inspected as described below. 43 44The new ALPS touchpads have an E7 signature of 73-03-50 or 73-03-0A but 45seem to be better differentiated by the EC Command Mode response. 46 47Command Mode 48------------ 49 50Protocol versions 3 and 4 have a command mode that is used to read and write 51one-byte device registers in a 16-bit address space. The command sequence 52EC-EC-EC-E9 places the device in command mode, and the device will respond 53with 88-07 followed by a third byte. This third byte can be used to determine 54whether the devices uses the version 3 or 4 protocol. 55 56To exit command mode, PSMOUSE_CMD_SETSTREAM (EA) is sent to the touchpad. 57 58While in command mode, register addresses can be set by first sending a 59specific command, either EC for v3 devices or F5 for v4 devices. Then the 60address is sent one nibble at a time, where each nibble is encoded as a 61command with optional data. This enoding differs slightly between the v3 and 62v4 protocols. 63 64Once an address has been set, the addressed register can be read by sending 65PSMOUSE_CMD_GETINFO (E9). The first two bytes of the response contains the 66address of the register being read, and the third contains the value of the 67register. Registers are written by writing the value one nibble at a time 68using the same encoding used for addresses. 69 70For the new ALPS touchpads, the EC command is used to enter command 71mode. The response in the new ALPS touchpads is significantly different, 72and more important in determining the behavior. This code has been 73separated from the original alps_model_data table and put in the 74alps_identify function. For example, there seem to be two hardware init 75sequences for the "Dolphin" touchpads as determined by the second byte 76of the EC response. 77 78Packet Format 79------------- 80 81In the following tables, the following notation is used. 82 83 CAPITALS = stick, miniscules = touchpad 84 85?'s can have different meanings on different models, such as wheel rotation, 86extra buttons, stick buttons on a dualpoint, etc. 87 88PS/2 packet format 89------------------ 90 91 byte 0: 0 0 YSGN XSGN 1 M R L 92 byte 1: X7 X6 X5 X4 X3 X2 X1 X0 93 byte 2: Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0 94 95Note that the device never signals overflow condition. 96 97ALPS Absolute Mode - Protocol Verion 1 98-------------------------------------- 99 100 byte 0: 1 0 0 0 1 x9 x8 x7 101 byte 1: 0 x6 x5 x4 x3 x2 x1 x0 102 byte 2: 0 ? ? l r ? fin ges 103 byte 3: 0 ? ? ? ? y9 y8 y7 104 byte 4: 0 y6 y5 y4 y3 y2 y1 y0 105 byte 5: 0 z6 z5 z4 z3 z2 z1 z0 106 107ALPS Absolute Mode - Protocol Version 2 108--------------------------------------- 109 110 byte 0: 1 ? ? ? 1 ? ? ? 111 byte 1: 0 x6 x5 x4 x3 x2 x1 x0 112 byte 2: 0 x10 x9 x8 x7 ? fin ges 113 byte 3: 0 y9 y8 y7 1 M R L 114 byte 4: 0 y6 y5 y4 y3 y2 y1 y0 115 byte 5: 0 z6 z5 z4 z3 z2 z1 z0 116 117Dualpoint device -- interleaved packet format 118--------------------------------------------- 119 120 byte 0: 1 1 0 0 1 1 1 1 121 byte 1: 0 x6 x5 x4 x3 x2 x1 x0 122 byte 2: 0 x10 x9 x8 x7 0 fin ges 123 byte 3: 0 0 YSGN XSGN 1 1 1 1 124 byte 4: X7 X6 X5 X4 X3 X2 X1 X0 125 byte 5: Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0 126 byte 6: 0 y9 y8 y7 1 m r l 127 byte 7: 0 y6 y5 y4 y3 y2 y1 y0 128 byte 8: 0 z6 z5 z4 z3 z2 z1 z0 129 130ALPS Absolute Mode - Protocol Version 3 131--------------------------------------- 132 133ALPS protocol version 3 has three different packet formats. The first two are 134associated with touchpad events, and the third is associatd with trackstick 135events. 136 137The first type is the touchpad position packet. 138 139 byte 0: 1 ? x1 x0 1 1 1 1 140 byte 1: 0 x10 x9 x8 x7 x6 x5 x4 141 byte 2: 0 y10 y9 y8 y7 y6 y5 y4 142 byte 3: 0 M R L 1 m r l 143 byte 4: 0 mt x3 x2 y3 y2 y1 y0 144 byte 5: 0 z6 z5 z4 z3 z2 z1 z0 145 146Note that for some devices the trackstick buttons are reported in this packet, 147and on others it is reported in the trackstick packets. 148 149The second packet type contains bitmaps representing the x and y axes. In the 150bitmaps a given bit is set if there is a finger covering that position on the 151given axis. Thus the bitmap packet can be used for low-resolution multi-touch 152data, although finger tracking is not possible. This packet also encodes the 153number of contacts (f1 and f0 in the table below). 154 155 byte 0: 1 1 x1 x0 1 1 1 1 156 byte 1: 0 x8 x7 x6 x5 x4 x3 x2 157 byte 2: 0 y7 y6 y5 y4 y3 y2 y1 158 byte 3: 0 y10 y9 y8 1 1 1 1 159 byte 4: 0 x14 x13 x12 x11 x10 x9 y0 160 byte 5: 0 1 ? ? ? ? f1 f0 161 162This packet only appears after a position packet with the mt bit set, and 163usually only appears when there are two or more contacts (although 164occasionally it's seen with only a single contact). 165 166The final v3 packet type is the trackstick packet. 167 168 byte 0: 1 1 x7 y7 1 1 1 1 169 byte 1: 0 x6 x5 x4 x3 x2 x1 x0 170 byte 2: 0 y6 y5 y4 y3 y2 y1 y0 171 byte 3: 0 1 0 0 1 0 0 0 172 byte 4: 0 z4 z3 z2 z1 z0 ? ? 173 byte 5: 0 0 1 1 1 1 1 1 174 175ALPS Absolute Mode - Protocol Version 4 176--------------------------------------- 177 178Protocol version 4 has an 8-byte packet format. 179 180 byte 0: 1 ? x1 x0 1 1 1 1 181 byte 1: 0 x10 x9 x8 x7 x6 x5 x4 182 byte 2: 0 y10 y9 y8 y7 y6 y5 y4 183 byte 3: 0 1 x3 x2 y3 y2 y1 y0 184 byte 4: 0 ? ? ? 1 ? r l 185 byte 5: 0 z6 z5 z4 z3 z2 z1 z0 186 byte 6: bitmap data (described below) 187 byte 7: bitmap data (described below) 188 189The last two bytes represent a partial bitmap packet, with 3 full packets 190required to construct a complete bitmap packet. Once assembled, the 6-byte 191bitmap packet has the following format: 192 193 byte 0: 0 1 x7 x6 x5 x4 x3 x2 194 byte 1: 0 x1 x0 y4 y3 y2 y1 y0 195 byte 2: 0 0 ? x14 x13 x12 x11 x10 196 byte 3: 0 x9 x8 y9 y8 y7 y6 y5 197 byte 4: 0 0 0 0 0 0 0 0 198 byte 5: 0 0 0 0 0 0 0 y10 199 200There are several things worth noting here. 201 202 1) In the bitmap data, bit 6 of byte 0 serves as a sync byte to 203 identify the first fragment of a bitmap packet. 204 205 2) The bitmaps represent the same data as in the v3 bitmap packets, although 206 the packet layout is different. 207 208 3) There doesn't seem to be a count of the contact points anywhere in the v4 209 protocol packets. Deriving a count of contact points must be done by 210 analyzing the bitmaps. 211 212 4) There is a 3 to 1 ratio of position packets to bitmap packets. Therefore 213 MT position can only be updated for every third ST position update, and 214 the count of contact points can only be updated every third packet as 215 well. 216 217So far no v4 devices with tracksticks have been encountered. 218 219ALPS Absolute Mode - Protocol Version 5 220--------------------------------------- 221This is basically Protocol Version 3 but with different logic for packet 222decode. It uses the same alps_process_touchpad_packet_v3 call with a 223specialized decode_fields function pointer to correctly interpret the 224packets. This appears to only be used by the Dolphin devices. 225 226For single-touch, the 6-byte packet format is: 227 228 byte 0: 1 1 0 0 1 0 0 0 229 byte 1: 0 x6 x5 x4 x3 x2 x1 x0 230 byte 2: 0 y6 y5 y4 y3 y2 y1 y0 231 byte 3: 0 M R L 1 m r l 232 byte 4: y10 y9 y8 y7 x10 x9 x8 x7 233 byte 5: 0 z6 z5 z4 z3 z2 z1 z0 234 235For mt, the format is: 236 237 byte 0: 1 1 1 n3 1 n2 n1 x24 238 byte 1: 1 y7 y6 y5 y4 y3 y2 y1 239 byte 2: ? x2 x1 y12 y11 y10 y9 y8 240 byte 3: 0 x23 x22 x21 x20 x19 x18 x17 241 byte 4: 0 x9 x8 x7 x6 x5 x4 x3 242 byte 5: 0 x16 x15 x14 x13 x12 x11 x10 243