1 Users Guide to Joystick Usage Under FlightGear Flight Simulator
3 Author John Check <j4strngs@rockfish.net>
5 This document is written with versions of FlightGear 0.7.5 and greater
6 in mind. It assumes a working joystick present on your system. While it
7 is written from the point of view of a Linux user, the cross platform
8 nature of FGFS should ensure the information presented is useful on other
9 platforms. I'd like to say thanks to all the developers who make FGFS happen
10 and forgive me for not giving credit with regard to the property
11 manager and js_demo. Corrections and additions are encouraged.
14 Earlier versions of FGFS had assignments of joystick axis/buttons
15 hard coded. If you had a joystick that did not use the default channel
16 assignments, you had to edit the source code and recompile.
17 Fortunately, around about v0.7.4/0.7.5 a "property manager" was
18 implemented, allowing, among other things, runtime access to some of the FGFS
19 internals, which facilitated being able to set the parameters for the
22 About runtime options:
23 FGFS has always had a plethora of available runtime options. Starting
24 point, altitude, direction, time of day and other aspects of the
25 simulated environment were always well represented. However there
26 were also a number of options and features that were not well documented.
27 Among these was the ability to use a runtime configuration file (.fgfsrc)
28 to control the default operation. The .fgfsrc file is not created at runtime
29 and must be created manually. Fortunately, the format of the file is
30 straightforward. All one need do is place the commandline options one would
31 like in a plain ASCII text file in the users home directory.
33 With the advent of the property manager it became possible to add a number
34 of additional runtime options to the .fgfsrc file including joystick channel
35 assignments. Basically, anything* that is reported by the property manager
36 can now be tweaked without having to recompile the binary.
38 *see mini-doc/properties.txt for exceptions
40 Determining your joystick output:
42 Included with FlightGear is a utility called js_demo. It will report
43 the number of joysticks attached to a system and their capabilites.
44 By observing the output of js_demo while working our joystick we can
45 determine what controls are where.
46 It should be noted that, at least on UNIX, numbering generally starts with
47 zero. In the following example the system has 1 joystick (js0) connected.
48 The output shown is from an analog Gravis BlackHawk with four buttons and
51 Typical output of js_demo:
53 Joystick test program.
54 ~~~~~~~~~~~~~~~~~~~~~~
55 Joystick 1 not detected
56 Joystick 2 not detected
57 +---------------JS.0-----------------+
58 | Btns Ax:0 Ax:1 Ax:2 |
59 +------------------------------------+
60 | 0000 +0.0 +0.0 -1.0 . . . |
62 It appears that the number of detected buttons is represented by the number of
63 "0"s. Clicking the actual buttons will result in the rightmost 0 changing to
64 the button number output. i.e. pressing button one will change the display to
65 look like this: 0001. It should be noted that this is a hexadecimal (base16)
66 number +1. Hex numbers start at 0, so this number is incremented by one for
67 hopefully obvious reasons.
69 Default Joystick properties:
77 Button 2 = Right brake
78 Button 3 = Elevator trim (up)
79 Button 4 = Elevator trim (down)
80 Button 5 = Flaps (down)
84 In addition to the channel assignments there are other parameters
85 that can be passed to FGFS.
91 This is an area where signals are ignored. It is used to compensate
92 for noise or potentiometers of dubious quality by creating a threshold
93 below which any signal is ignored. It it written as a decimal number or "float"
94 with a typical value of 0.1 for elevators and ailerons, 0.0 for throttle
98 This number, also written as a float, will control sensitivity of an axis.
99 Negating the number will result in the control moving counter to the default.
100 A typical value is 1.0. In my case, throttle behaviour was inverted from what
101 I preferred. I set this value to -1.0 and everything was groovy.
105 Also a float. Used to maximize a controls use of it's axis, as in the case of a
106 throttle where zero would be a minimum and not a center point like in the case
107 of a rudder. Typical value -1.0 (Am I close? Anybody?)
113 A button designated a switch is either on or off. While the button is
114 held in the switch is engaged. Brakes are described as a switch and take
115 additional parameters [ step, repeatable ]
118 A button designated adjust is for controls that have a range
119 of settings, for example elevator trim and flaps. These are found
120 in pairs having opposing values for the parameter 'step'.
121 The 'repeatable' parameter should be appropriate to the type of control.
124 This defines how much adjustment is applied when the button is activated
125 Default values are 1.0 for brakes (full on), 0.001 / -0.001 for
126 elevator trim and -0.34 / 0.34 for flaps
129 In this case repeatable means when the button is held down the value continues
130 to increment. repeatable is a true / false value. The default for brakes is
131 false. This is appropriate since by default brakes are a switch that are full
132 on (right?) Elevator trim on the other hand defaults to true. Holding down the
133 button for elevator trim will cause a continuous adjustment until the button
134 is released. Being a fine adjustment this is appropriate behaviour. Flaps
135 on the otherhand default to false. Clicking the flaps button will cause the
136 flaps to be extended to the first detent, subsequent clicks will extend or
137 retract by one increment. Being a large adjustment with a major impact on a
138 planes handling this is a good thing.
140 Syntax for properties in .fgfsrc
142 Here is a listing of the defaults as they would appear in .fgfsrc
143 You only need entries where the defaults aren't what you want.
144 In my case I had to make entries to put the throttle on axis2.
146 // Default axis 0 to aileron
147 --prop:/input/js0/axis0/control=/controls/aileron
148 --prop:/input/js0/axis0/dead-band=0.1
150 // Default axis 1 to elevator
151 --prop:/input/js0/axis1/control=/controls/elevator"
152 --prop:/input/js0/axis1/dead-band=0.1
153 --prop:/input/js0/axis1/factor=-1.0
155 // Default axis 2 to rudder
156 --prop:/input/js0/axis2/control=/controls/rudder
157 --prop:/input/js0/axis2/dead-band=0.1
159 // Default axis 3 to throttle
160 --prop:/input/js0/axis3/control=/controls/throttle
161 --prop:/input/js0/axis3/dead-band=0.0
162 --prop:/input/js0/axis3/offset=-1.0
163 --prop:/input/js0/axis3/factor=-0.5
165 // Default button 0 to all brakes
166 --prop:/input/js0/button0/action=switch
167 --prop:/input/js0/button0/control=/controls/brakes/all
168 --prop:/input/js0/button0/step=1.0
169 --prop:/input/js0/button0/repeatable=false
171 // Default button 1 to left brake.
172 --prop:/input/js0/button1/action=switch
173 --prop:/input/js0/button1/control=/controls/brakes/left
174 --prop:/input/js0/button1/step=1.0
175 --prop:/input/js0/button1/repeatable=false
177 // Default button 2 to right brake.
178 --prop:/input/js0/button2/action=switch
179 --prop:/input/js0/button2/control=/controls/brakes/right
180 --prop:/input/js0/button2/step=1.0
181 --prop:/input/js0/button2/repeatable=false
183 // Default buttons 3 and 4 to elevator trim
184 --prop:/input/js0/button3/action=adjust
185 --prop:/input/js0/button3/control=/controls/elevator-trim
186 --prop:/input/js0/button3/step=0.001
187 --prop:/input/js0/button3/repeatable=true
189 --prop:/input/js0/button4/action=adjust
190 --prop:/input/js0/button4/control=/controls/elevator-trim
191 --prop:/iput/js0/button4/step=0.001
192 --prop:/input/js0/button4/repeatable=true
194 // Default buttons 5 and 6 to flaps
195 --prop:/input/js0/button5/action=adjust
196 --prop:/input/js0/button5/control=/controls/flaps
197 --prop:/input/js0/button5/step=-0.34
198 --prop:/input/js0/button5/repeatable=false
200 --prop:/input/js0/button6/action=adjust
201 --prop:/input/js0/button6/control=/controls/flaps"
202 --prop:/input/js0/button6/step=0.34
203 --prop:/input/js0/button6/repeatable=false