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1 | ** Introduction | ||
2 | This document describes what I managed to discover about the protocol used to | ||
3 | specify force effects to I-Force 2.0 devices. None of this information comes | ||
4 | from Immerse. That's why you should not trust what is written in this | ||
5 | document. This document is intended to help understanding the protocol. | ||
6 | This is not a reference. Comments and corrections are welcome. To contact me, | ||
7 | send an email to: deneux@ifrance.com | ||
8 | |||
9 | ** WARNING ** | ||
10 | I may not be held responsible for any dammage or harm caused if you try to | ||
11 | send data to your I-Force device based on what you read in this document. | ||
12 | |||
13 | ** Preliminary Notes: | ||
14 | All values are hexadecimal with big-endian encoding (msb on the left). Beware, | ||
15 | values inside packets are encoded using little-endian. Bytes whose roles are | ||
16 | unknown are marked ??? Information that needs deeper inspection is marked (?) | ||
17 | |||
18 | ** General form of a packet ** | ||
19 | This is how packets look when the device uses the rs232 to communicate. | ||
20 | 2B OP LEN DATA CS | ||
21 | CS is the checksum. It is equal to the exclusive or of all bytes. | ||
22 | |||
23 | When using USB: | ||
24 | OP DATA | ||
25 | The 2B, LEN and CS fields have disappeared, probably because USB handles frames and | ||
26 | data corruption is handled or unsignificant. | ||
27 | |||
28 | First, I describe effects that are sent by the device to the computer | ||
29 | |||
30 | ** Device input state | ||
31 | This packet is used to indicate the state of each button and the value of each | ||
32 | axis | ||
33 | OP= 01 for a joystick, 03 for a wheel | ||
34 | LEN= Varies from device to device | ||
35 | 00 X-Axis lsb | ||
36 | 01 X-Axis msb | ||
37 | 02 Y-Axis lsb, or gas pedal for a wheel | ||
38 | 03 Y-Axis msb, or brake pedal for a wheel | ||
39 | 04 Throttle | ||
40 | 05 Buttons | ||
41 | 06 Lower 4 bits: Buttons | ||
42 | Upper 4 bits: Hat | ||
43 | 07 Rudder | ||
44 | |||
45 | ** Device effects states | ||
46 | OP= 02 | ||
47 | LEN= Varies | ||
48 | 00 ? Bit 1 (Value 2) is the value of the deadman switch | ||
49 | 01 Bit 8 is set if the effect is playing. Bits 0 to 7 are the effect id. | ||
50 | 02 ?? | ||
51 | 03 Address of parameter block changed (lsb) | ||
52 | 04 Address of parameter block changed (msb) | ||
53 | 05 Address of second parameter block changed (lsb) | ||
54 | ... depending on the number of parameter blocks updated | ||
55 | |||
56 | ** Force effect ** | ||
57 | OP= 01 | ||
58 | LEN= 0e | ||
59 | 00 Channel (when playing several effects at the same time, each must be assigned a channel) | ||
60 | 01 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 | |||
71 | 02 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 | |||
80 | 03-04 Duration of effect (little endian encoding, in ms) | ||
81 | |||
82 | 05 Direction of effect, if applicable. Else, see 02 for value to assign. | ||
83 | |||
84 | 06-07 Minimum time between triggering. | ||
85 | |||
86 | 08-09 Address of periodicity or magnitude parameters | ||
87 | 0a-0b Address of attack and fade parameters, or ffff if none. | ||
88 | *or* | ||
89 | 08-09 Address of interactive parameters for X-axis, or ffff if not applicable | ||
90 | 0a-0b Address of interactive parameters for Y-axis, or ffff if not applicable | ||
91 | |||
92 | 0c-0d Delay before execution of effect (little endian encoding, in ms) | ||
93 | |||
94 | |||
95 | ** Time based parameters ** | ||
96 | |||
97 | *** Attack and fade *** | ||
98 | OP= 02 | ||
99 | LEN= 08 | ||
100 | 00-01 Address where to store the parameteres | ||
101 | 02-03 Duration of attack (little endian encoding, in ms) | ||
102 | 04 Level at end of attack. Signed byte. | ||
103 | 05-06 Duration of fade. | ||
104 | 07 Level at end of fade. | ||
105 | |||
106 | *** Magnitude *** | ||
107 | OP= 03 | ||
108 | LEN= 03 | ||
109 | 00-01 Address | ||
110 | 02 Level. Signed byte. | ||
111 | |||
112 | *** Periodicity *** | ||
113 | OP= 04 | ||
114 | LEN= 07 | ||
115 | 00-01 Address | ||
116 | 02 Magnitude. Signed byte. | ||
117 | 03 Offset. Signed byte. | ||
118 | 04 Phase. Val 00 = 0 deg, Val 40 = 90 degs. | ||
119 | 05-06 Period (little endian encoding, in ms) | ||
120 | |||
121 | ** Interactive parameters ** | ||
122 | OP= 05 | ||
123 | LEN= 0a | ||
124 | 00-01 Address | ||
125 | 02 Positive Coeff | ||
126 | 03 Negative Coeff | ||
127 | 04+05 Offset (center) | ||
128 | 06+07 Dead band (Val 01F4 = 5000 (decimal)) | ||
129 | 08 Positive saturation (Val 0a = 1000 (decimal) Val 64 = 10000 (decimal)) | ||
130 | 09 Negative saturation | ||
131 | |||
132 | The encoding is a bit funny here: For coeffs, these are signed values. The | ||
133 | maximum value is 64 (100 decimal), the min is 9c. | ||
134 | For the offset, the minimum value is FE0C, the maximum value is 01F4. | ||
135 | For the deadband, the minimum value is 0, the max is 03E8. | ||
136 | |||
137 | ** Controls ** | ||
138 | OP= 41 | ||
139 | LEN= 03 | ||
140 | 00 Channel | ||
141 | 01 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) | ||
145 | 02 Number of iterations n. | ||
146 | |||
147 | ** Init ** | ||
148 | |||
149 | *** Querying features *** | ||
150 | OP= ff | ||
151 | Query command. Length varies according to the query type. | ||
152 | The general format of this packet is: | ||
153 | ff 01 QUERY [INDEX] CHECKSUM | ||
154 | reponses are of the same form: | ||
155 | FF LEN QUERY VALUE_QUERIED CHECKSUM2 | ||
156 | where LEN = 1 + length(VALUE_QUERIED) | ||
157 | |||
158 | **** Query ram size **** | ||
159 | QUERY = 42 ('B'uffer size) | ||
160 | The device should reply with the same packet plus two additionnal bytes | ||
161 | containing the size of the memory: | ||
162 | ff 03 42 03 e8 CS would mean that the device has 1000 bytes of ram available. | ||
163 | |||
164 | **** Query number of effects **** | ||
165 | QUERY = 4e ('N'umber of effects) | ||
166 | The device should respond by sending the number of effects that can be played | ||
167 | at the same time (one byte) | ||
168 | ff 02 4e 14 CS would stand for 20 effects. | ||
169 | |||
170 | **** Vendor's id **** | ||
171 | QUERY = 4d ('M'anufacturer) | ||
172 | Query the vendors'id (2 bytes) | ||
173 | |||
174 | **** Product id ***** | ||
175 | QUERY = 50 ('P'roduct) | ||
176 | Query the product id (2 bytes) | ||
177 | |||
178 | **** Open device **** | ||
179 | QUERY = 4f ('O'pen) | ||
180 | No data returned. | ||
181 | |||
182 | **** Close device ***** | ||
183 | QUERY = 43 ('C')lose | ||
184 | No data returned. | ||
185 | |||
186 | **** Query effect **** | ||
187 | QUERY = 45 ('E') | ||
188 | Send effect type. | ||
189 | Returns nonzero if supported (2 bytes) | ||
190 | |||
191 | **** Firmware Version **** | ||
192 | QUERY = 56 ('V'ersion) | ||
193 | Sends 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 !!! | ||
199 | OP= 40 <idx> <val> [<val>] | ||
200 | LEN= 2 or 3 | ||
201 | 00 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 **** | ||
210 | OP= 42 <val> | ||
211 | LEN= 1 | ||
212 | 00 State | ||
213 | Bit 3 Pause force feedback | ||
214 | Bit 2 Enable force feedback | ||
215 | Bit 0 Stop all effects | ||
216 | |||
217 | **** Set overall gain **** | ||
218 | OP= 43 <val> | ||
219 | LEN= 1 | ||
220 | 00 Gain | ||
221 | Val 00 = 0% | ||
222 | Val 40 = 50% | ||
223 | Val 80 = 100% | ||
224 | |||
225 | ** Parameter memory ** | ||
226 | |||
227 | Each device has a certain amount of memory to store parameters of effects. | ||
228 | The amount of RAM may vary, I encountered values from 200 to 1000 bytes. Below | ||
229 | is 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 | |||
237 | 1. Generate effects using the force editor provided with the DirectX SDK, or use Immersion Studio (freely available at their web site in the developer section: www.immersion.com) | ||
238 | 2. Start a soft spying RS232 or USB (depending on where you connected your joystick/wheel). I used ComPortSpy from fCoder (alpha version!) | ||
239 | 3. Play the effect, and watch what happens on the spy screen. | ||
240 | |||
241 | A few words about ComPortSpy: | ||
242 | At first glance, this soft seems, hum, well... buggy. In fact, data appear with a few seconds latency. Personnaly, I restart it every time I play an effect. | ||
243 | Remember it's free (as in free beer) and alpha! | ||
244 | |||
245 | ** URLS ** | ||
246 | Check www.immerse.com for Immersion Studio, and www.fcoder.com for ComPortSpy. | ||
247 | |||
248 | ** Author of this document ** | ||
249 | Johann Deneux <deneux@ifrance.com> | ||
250 | Home page at http://www.esil.univ-mrs.fr/~jdeneux/projects/ff/ | ||
251 | |||
252 | Additions by Vojtech Pavlik. | ||
253 | |||
254 | I-Force is trademark of Immersion Corp. | ||