iforce-protocol.rst (8670B)
1=============== 2Iforce Protocol 3=============== 4 5:Author: Johann Deneux <johann.deneux@gmail.com> 6 7Home page at `<http://web.archive.org/web/*/http://www.esil.univ-mrs.fr>`_ 8 9:Additions: by Vojtech Pavlik. 10 11 12Introduction 13============ 14 15This document describes what I managed to discover about the protocol used to 16specify force effects to I-Force 2.0 devices. None of this information comes 17from Immerse. That's why you should not trust what is written in this 18document. This document is intended to help understanding the protocol. 19This is not a reference. Comments and corrections are welcome. To contact me, 20send an email to: johann.deneux@gmail.com 21 22.. warning:: 23 24 I shall not be held responsible for any damage or harm caused if you try to 25 send data to your I-Force device based on what you read in this document. 26 27Preliminary Notes 28================= 29 30All values are hexadecimal with big-endian encoding (msb on the left). Beware, 31values inside packets are encoded using little-endian. Bytes whose roles are 32unknown are marked ??? Information that needs deeper inspection is marked (?) 33 34General form of a packet 35------------------------ 36 37This is how packets look when the device uses the rs232 to communicate. 38 39== == === ==== == 402B OP LEN DATA CS 41== == === ==== == 42 43CS is the checksum. It is equal to the exclusive or of all bytes. 44 45When using USB: 46 47== ==== 48OP DATA 49== ==== 50 51The 2B, LEN and CS fields have disappeared, probably because USB handles 52frames and data corruption is handled or unsignificant. 53 54First, I describe effects that are sent by the device to the computer 55 56Device input state 57================== 58 59This packet is used to indicate the state of each button and the value of each 60axis:: 61 62 OP= 01 for a joystick, 03 for a wheel 63 LEN= Varies from device to device 64 00 X-Axis lsb 65 01 X-Axis msb 66 02 Y-Axis lsb, or gas pedal for a wheel 67 03 Y-Axis msb, or brake pedal for a wheel 68 04 Throttle 69 05 Buttons 70 06 Lower 4 bits: Buttons 71 Upper 4 bits: Hat 72 07 Rudder 73 74Device effects states 75===================== 76 77:: 78 79 OP= 02 80 LEN= Varies 81 00 ? Bit 1 (Value 2) is the value of the deadman switch 82 01 Bit 8 is set if the effect is playing. Bits 0 to 7 are the effect id. 83 02 ?? 84 03 Address of parameter block changed (lsb) 85 04 Address of parameter block changed (msb) 86 05 Address of second parameter block changed (lsb) 87 ... depending on the number of parameter blocks updated 88 89Force effect 90------------ 91 92:: 93 94 OP= 01 95 LEN= 0e 96 00 Channel (when playing several effects at the same time, each must 97 be assigned a channel) 98 01 Wave form 99 Val 00 Constant 100 Val 20 Square 101 Val 21 Triangle 102 Val 22 Sine 103 Val 23 Sawtooth up 104 Val 24 Sawtooth down 105 Val 40 Spring (Force = f(pos)) 106 Val 41 Friction (Force = f(velocity)) and Inertia 107 (Force = f(acceleration)) 108 109 110 02 Axes affected and trigger 111 Bits 4-7: Val 2 = effect along one axis. Byte 05 indicates direction 112 Val 4 = X axis only. Byte 05 must contain 5a 113 Val 8 = Y axis only. Byte 05 must contain b4 114 Val c = X and Y axes. Bytes 05 must contain 60 115 Bits 0-3: Val 0 = No trigger 116 Val x+1 = Button x triggers the effect 117 When the whole byte is 0, cancel the previously set trigger 118 119 03-04 Duration of effect (little endian encoding, in ms) 120 121 05 Direction of effect, if applicable. Else, see 02 for value to assign. 122 123 06-07 Minimum time between triggering. 124 125 08-09 Address of periodicity or magnitude parameters 126 0a-0b Address of attack and fade parameters, or ffff if none. 127 *or* 128 08-09 Address of interactive parameters for X-axis, 129 or ffff if not applicable 130 0a-0b Address of interactive parameters for Y-axis, 131 or ffff if not applicable 132 133 0c-0d Delay before execution of effect (little endian encoding, in ms) 134 135 136Time based parameters 137--------------------- 138 139Attack and fade 140^^^^^^^^^^^^^^^ 141 142:: 143 144 OP= 02 145 LEN= 08 146 00-01 Address where to store the parameters 147 02-03 Duration of attack (little endian encoding, in ms) 148 04 Level at end of attack. Signed byte. 149 05-06 Duration of fade. 150 07 Level at end of fade. 151 152Magnitude 153^^^^^^^^^ 154 155:: 156 157 OP= 03 158 LEN= 03 159 00-01 Address 160 02 Level. Signed byte. 161 162Periodicity 163^^^^^^^^^^^ 164 165:: 166 167 OP= 04 168 LEN= 07 169 00-01 Address 170 02 Magnitude. Signed byte. 171 03 Offset. Signed byte. 172 04 Phase. Val 00 = 0 deg, Val 40 = 90 degs. 173 05-06 Period (little endian encoding, in ms) 174 175Interactive parameters 176---------------------- 177 178:: 179 180 OP= 05 181 LEN= 0a 182 00-01 Address 183 02 Positive Coeff 184 03 Negative Coeff 185 04+05 Offset (center) 186 06+07 Dead band (Val 01F4 = 5000 (decimal)) 187 08 Positive saturation (Val 0a = 1000 (decimal) Val 64 = 10000 (decimal)) 188 09 Negative saturation 189 190The encoding is a bit funny here: For coeffs, these are signed values. The 191maximum value is 64 (100 decimal), the min is 9c. 192For the offset, the minimum value is FE0C, the maximum value is 01F4. 193For the deadband, the minimum value is 0, the max is 03E8. 194 195Controls 196-------- 197 198:: 199 200 OP= 41 201 LEN= 03 202 00 Channel 203 01 Start/Stop 204 Val 00: Stop 205 Val 01: Start and play once. 206 Val 41: Start and play n times (See byte 02 below) 207 02 Number of iterations n. 208 209Init 210---- 211 212 213Querying features 214^^^^^^^^^^^^^^^^^ 215:: 216 217 OP= ff 218 Query command. Length varies according to the query type. 219 The general format of this packet is: 220 ff 01 QUERY [INDEX] CHECKSUM 221 responses are of the same form: 222 FF LEN QUERY VALUE_QUERIED CHECKSUM2 223 where LEN = 1 + length(VALUE_QUERIED) 224 225Query ram size 226~~~~~~~~~~~~~~ 227 228:: 229 230 QUERY = 42 ('B'uffer size) 231 232The device should reply with the same packet plus two additional bytes 233containing the size of the memory: 234ff 03 42 03 e8 CS would mean that the device has 1000 bytes of ram available. 235 236Query number of effects 237~~~~~~~~~~~~~~~~~~~~~~~ 238 239:: 240 241 QUERY = 4e ('N'umber of effects) 242 243The device should respond by sending the number of effects that can be played 244at the same time (one byte) 245ff 02 4e 14 CS would stand for 20 effects. 246 247Vendor's id 248~~~~~~~~~~~ 249 250:: 251 252 QUERY = 4d ('M'anufacturer) 253 254Query the vendors'id (2 bytes) 255 256Product id 257~~~~~~~~~~ 258 259:: 260 261 QUERY = 50 ('P'roduct) 262 263Query the product id (2 bytes) 264 265Open device 266~~~~~~~~~~~ 267 268:: 269 270 QUERY = 4f ('O'pen) 271 272No data returned. 273 274Close device 275~~~~~~~~~~~~ 276 277:: 278 279 QUERY = 43 ('C')lose 280 281No data returned. 282 283Query effect 284~~~~~~~~~~~~ 285 286:: 287 288 QUERY = 45 ('E') 289 290Send effect type. 291Returns nonzero if supported (2 bytes) 292 293Firmware Version 294~~~~~~~~~~~~~~~~ 295 296:: 297 298 QUERY = 56 ('V'ersion) 299 300Sends back 3 bytes - major, minor, subminor 301 302Initialisation of the device 303^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 304 305Set Control 306~~~~~~~~~~~ 307 308.. note:: 309 Device dependent, can be different on different models! 310 311:: 312 313 OP= 40 <idx> <val> [<val>] 314 LEN= 2 or 3 315 00 Idx 316 Idx 00 Set dead zone (0..2048) 317 Idx 01 Ignore Deadman sensor (0..1) 318 Idx 02 Enable comm watchdog (0..1) 319 Idx 03 Set the strength of the spring (0..100) 320 Idx 04 Enable or disable the spring (0/1) 321 Idx 05 Set axis saturation threshold (0..2048) 322 323Set Effect State 324~~~~~~~~~~~~~~~~ 325 326:: 327 328 OP= 42 <val> 329 LEN= 1 330 00 State 331 Bit 3 Pause force feedback 332 Bit 2 Enable force feedback 333 Bit 0 Stop all effects 334 335Set overall 336~~~~~~~~~~~ 337 338:: 339 340 OP= 43 <val> 341 LEN= 1 342 00 Gain 343 Val 00 = 0% 344 Val 40 = 50% 345 Val 80 = 100% 346 347Parameter memory 348---------------- 349 350Each device has a certain amount of memory to store parameters of effects. 351The amount of RAM may vary, I encountered values from 200 to 1000 bytes. Below 352is the amount of memory apparently needed for every set of parameters: 353 354 - period : 0c 355 - magnitude : 02 356 - attack and fade : 0e 357 - interactive : 08 358 359Appendix: How to study the protocol? 360==================================== 361 3621. Generate effects using the force editor provided with the DirectX SDK, or 363use Immersion Studio (freely available at their web site in the developer section: 364www.immersion.com) 3652. Start a soft spying RS232 or USB (depending on where you connected your 366joystick/wheel). I used ComPortSpy from fCoder (alpha version!) 3673. Play the effect, and watch what happens on the spy screen. 368 369A few words about ComPortSpy: 370At first glance, this software seems, hum, well... buggy. In fact, data appear with a 371few seconds latency. Personally, I restart it every time I play an effect. 372Remember it's free (as in free beer) and alpha! 373 374URLS 375==== 376 377Check http://www.immerse.com for Immersion Studio, 378and http://www.fcoder.com for ComPortSpy. 379 380 381I-Force is trademark of Immersion Corp.