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.
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