1** Introduction 2This document describes what I managed to discover about the protocol used to 3specify force effects to I-Force 2.0 devices. None of this information comes 4from Immerse. That's why you should not trust what is written in this 5document. This document is intended to help understanding the protocol. 6This is not a reference. Comments and corrections are welcome. To contact me, 7send an email to: johann.deneux@gmail.com 8 9** WARNING ** 10I shall not be held responsible for any damage or harm caused if you try to 11send data to your I-Force device based on what you read in this document. 12 13** Preliminary Notes: 14All values are hexadecimal with big-endian encoding (msb on the left). Beware, 15values inside packets are encoded using little-endian. Bytes whose roles are 16unknown are marked ??? Information that needs deeper inspection is marked (?) 17 18** General form of a packet ** 19This is how packets look when the device uses the rs232 to communicate. 202B OP LEN DATA CS 21CS is the checksum. It is equal to the exclusive or of all bytes. 22 23When using USB: 24OP DATA 25The 2B, LEN and CS fields have disappeared, probably because USB handles frames and 26data corruption is handled or unsignificant. 27 28First, I describe effects that are sent by the device to the computer 29 30** Device input state 31This packet is used to indicate the state of each button and the value of each 32axis 33OP= 01 for a joystick, 03 for a wheel 34LEN= Varies from device to device 3500 X-Axis lsb 3601 X-Axis msb 3702 Y-Axis lsb, or gas pedal for a wheel 3803 Y-Axis msb, or brake pedal for a wheel 3904 Throttle 4005 Buttons 4106 Lower 4 bits: Buttons 42 Upper 4 bits: Hat 4307 Rudder 44 45** Device effects states 46OP= 02 47LEN= Varies 4800 ? Bit 1 (Value 2) is the value of the deadman switch 4901 Bit 8 is set if the effect is playing. Bits 0 to 7 are the effect id. 5002 ?? 5103 Address of parameter block changed (lsb) 5204 Address of parameter block changed (msb) 5305 Address of second parameter block changed (lsb) 54... depending on the number of parameter blocks updated 55 56** Force effect ** 57OP= 01 58LEN= 0e 5900 Channel (when playing several effects at the same time, each must be assigned a channel) 6001 Wave form 61 Val 00 Constant 62 Val 20 Square 63 Val 21 Triangle 64 Val 22 Sine 65 Val 23 Sawtooth up 66 Val 24 Sawtooth down 67 Val 40 Spring (Force = f(pos)) 68 Val 41 Friction (Force = f(velocity)) and Inertia (Force = f(acceleration)) 69 70 7102 Axes affected and trigger 72 Bits 4-7: Val 2 = effect along one axis. Byte 05 indicates direction 73 Val 4 = X axis only. Byte 05 must contain 5a 74 Val 8 = Y axis only. Byte 05 must contain b4 75 Val c = X and Y axes. Bytes 05 must contain 60 76 Bits 0-3: Val 0 = No trigger 77 Val x+1 = Button x triggers the effect 78 When the whole byte is 0, cancel the previously set trigger 79 8003-04 Duration of effect (little endian encoding, in ms) 81 8205 Direction of effect, if applicable. Else, see 02 for value to assign. 83 8406-07 Minimum time between triggering. 85 8608-09 Address of periodicity or magnitude parameters 870a-0b Address of attack and fade parameters, or ffff if none. 88*or* 8908-09 Address of interactive parameters for X-axis, or ffff if not applicable 900a-0b Address of interactive parameters for Y-axis, or ffff if not applicable 91 920c-0d Delay before execution of effect (little endian encoding, in ms) 93 94 95** Time based parameters ** 96 97*** Attack and fade *** 98OP= 02 99LEN= 08 10000-01 Address where to store the parameters 10102-03 Duration of attack (little endian encoding, in ms) 10204 Level at end of attack. Signed byte. 10305-06 Duration of fade. 10407 Level at end of fade. 105 106*** Magnitude *** 107OP= 03 108LEN= 03 10900-01 Address 11002 Level. Signed byte. 111 112*** Periodicity *** 113OP= 04 114LEN= 07 11500-01 Address 11602 Magnitude. Signed byte. 11703 Offset. Signed byte. 11804 Phase. Val 00 = 0 deg, Val 40 = 90 degs. 11905-06 Period (little endian encoding, in ms) 120 121** Interactive parameters ** 122OP= 05 123LEN= 0a 12400-01 Address 12502 Positive Coeff 12603 Negative Coeff 12704+05 Offset (center) 12806+07 Dead band (Val 01F4 = 5000 (decimal)) 12908 Positive saturation (Val 0a = 1000 (decimal) Val 64 = 10000 (decimal)) 13009 Negative saturation 131 132The encoding is a bit funny here: For coeffs, these are signed values. The 133maximum value is 64 (100 decimal), the min is 9c. 134For the offset, the minimum value is FE0C, the maximum value is 01F4. 135For the deadband, the minimum value is 0, the max is 03E8. 136 137** Controls ** 138OP= 41 139LEN= 03 14000 Channel 14101 Start/Stop 142 Val 00: Stop 143 Val 01: Start and play once. 144 Val 41: Start and play n times (See byte 02 below) 14502 Number of iterations n. 146 147** Init ** 148 149*** Querying features *** 150OP= ff 151Query command. Length varies according to the query type. 152The general format of this packet is: 153ff 01 QUERY [INDEX] CHECKSUM 154responses are of the same form: 155FF LEN QUERY VALUE_QUERIED CHECKSUM2 156where LEN = 1 + length(VALUE_QUERIED) 157 158**** Query ram size **** 159QUERY = 42 ('B'uffer size) 160The device should reply with the same packet plus two additional bytes 161containing the size of the memory: 162ff 03 42 03 e8 CS would mean that the device has 1000 bytes of ram available. 163 164**** Query number of effects **** 165QUERY = 4e ('N'umber of effects) 166The device should respond by sending the number of effects that can be played 167at the same time (one byte) 168ff 02 4e 14 CS would stand for 20 effects. 169 170**** Vendor's id **** 171QUERY = 4d ('M'anufacturer) 172Query the vendors'id (2 bytes) 173 174**** Product id ***** 175QUERY = 50 ('P'roduct) 176Query the product id (2 bytes) 177 178**** Open device **** 179QUERY = 4f ('O'pen) 180No data returned. 181 182**** Close device ***** 183QUERY = 43 ('C')lose 184No data returned. 185 186**** Query effect **** 187QUERY = 45 ('E') 188Send effect type. 189Returns nonzero if supported (2 bytes) 190 191**** Firmware Version **** 192QUERY = 56 ('V'ersion) 193Sends back 3 bytes - major, minor, subminor 194 195*** Initialisation of the device *** 196 197**** Set Control **** 198!!! Device dependent, can be different on different models !!! 199OP= 40 <idx> <val> [<val>] 200LEN= 2 or 3 20100 Idx 202 Idx 00 Set dead zone (0..2048) 203 Idx 01 Ignore Deadman sensor (0..1) 204 Idx 02 Enable comm watchdog (0..1) 205 Idx 03 Set the strength of the spring (0..100) 206 Idx 04 Enable or disable the spring (0/1) 207 Idx 05 Set axis saturation threshold (0..2048) 208 209**** Set Effect State **** 210OP= 42 <val> 211LEN= 1 21200 State 213 Bit 3 Pause force feedback 214 Bit 2 Enable force feedback 215 Bit 0 Stop all effects 216 217**** Set overall gain **** 218OP= 43 <val> 219LEN= 1 22000 Gain 221 Val 00 = 0% 222 Val 40 = 50% 223 Val 80 = 100% 224 225** Parameter memory ** 226 227Each device has a certain amount of memory to store parameters of effects. 228The amount of RAM may vary, I encountered values from 200 to 1000 bytes. Below 229is the amount of memory apparently needed for every set of parameters: 230 - period : 0c 231 - magnitude : 02 232 - attack and fade : 0e 233 - interactive : 08 234 235** Appendix: How to study the protocol ? ** 236 2371. Generate effects using the force editor provided with the DirectX SDK, or 238use Immersion Studio (freely available at their web site in the developer section: 239www.immersion.com) 2402. Start a soft spying RS232 or USB (depending on where you connected your 241joystick/wheel). I used ComPortSpy from fCoder (alpha version!) 2423. Play the effect, and watch what happens on the spy screen. 243 244A few words about ComPortSpy: 245At first glance, this software seems, hum, well... buggy. In fact, data appear with a 246few seconds latency. Personally, I restart it every time I play an effect. 247Remember it's free (as in free beer) and alpha! 248 249** URLS ** 250Check www.immerse.com for Immersion Studio, and www.fcoder.com for ComPortSpy. 251 252** Author of this document ** 253Johann Deneux <johann.deneux@gmail.com> 254Home page at http://web.archive.org/web/*/http://www.esil.univ-mrs.fr 255 256Additions by Vojtech Pavlik. 257 258I-Force is trademark of Immersion Corp. 259