[PD] joysticks with hid

Hans-Christoph Steiner hans at eds.org
Sun Jan 29 07:20:49 CET 2006 

On Jan 28, 2006, at 10:57 PM, David Merrill wrote:

> Hi Hans -
>
> Hans-Christoph Steiner wrote:
>>
>> This is a bit of a quandary.  Currently [hid] maps all buttons to  
>> btn_0, btn_1, etc. whether its of the type BTN_MISC, BTN_MOUSE,  
>> BTN_JOYSTICK, BTN_GAMEPAD, BTN_DIGI, or BTN_WHEEL.  Axes are treated  
>> similarly.  This means patches that are written for a gamepad will  
>> also work for a joystick since all of the names are the same.  But  
>> this relies on manufacturer following the USB HID spec, which it  
>> seems only 50% do.  arg.
>>
>> So with the Microsoft Sidewinder gamepad, they are way off (its a  
>> gamepad, right?).  Btn3 is a BTN_MISC type and ThumbBtn2 is a  
>> BTN_JOYSTICK type.  So they are using BTN_MISC and BTN_JOYSTICK when  
>> they should be using only BTN_GAMEPAD.
> Hmm - I'm not sure if I would call it a gamepad - have a look at what  
> it looks like:
> http://www.linux-user.de/ausgabe/2000/11/035-usb-eingabe/sidewinder.jpg
> It has 2 continuous degrees of freedom, along with all of the buttons.  
> Maybe it's a gamepad, depending on what the definition of one is! :)

Call it a gamepad, call it a joystick, or call it a "MISC".  In any  
case, they should have used one button type consistently... I forgot to  
mention, these button types that I mentioned are actually the Linux  
interpretation of the USB HID spec, mostly its much better.  I wonder  
what the actual "proper" USB HID values are for all the buttons...

>> So my grand plan is to have platform-specific classes which give raw  
>> access to the USB HID info (i.e. [linuxinput], [darwinhid],  
>> [windowshid], and [directinput]).  I haven't had a need for those  
>> yet, so I haven't written them.  But you are in luck, [linuxevent]  
>> still works, and will give you raw access.  But keep in mind,  
>> [linuxevent] works differently than [hid], and is deprecated.  (Come  
>> to think of it, I'll probably do [windowshid] and [directinput] soon  
>> since there are fundamental problems with [hid] on Windows which  
>> aren't quite resolved yet.
> Ok, so for the short-term, I should use the linuxevent external then.  
> I'll have a look at that. So it sounds like it's too much trouble to  
> unify the [hid] external and have it work the same way everywhere  
> then? What would the difference be between [windowshid] and  
> [directinput] ?

[windowshid] would use the DDK HID API, and [directinput] would use the  
DirectX DirectInput API.  They are quite different.  DirectInput is  
quite easy, but also quite limited.  DDK HID is a standard HID  
implementation, very similar to Mac OS X's HID stuff, but they have the  
standard Microsoft-style arbitrary restrictions: the mouse and keyboard  
are exclusively locked by the OS, so you can open those devices for  
reading (i.e. you can't use them at all, except with DirectInput).

.hc

> -Dave
>>
>>
>> .hc
>>
>> On Jan 28, 2006, at 5:33 PM, David Merrill wrote:
>>
>>> Hello again hans & everyone -
>>>
>>> I have a little more detail, after some investigation. I found an  
>>> article that describes what I think is responsible for the spurious  
>>> button presses, at:
>>>
>>> http://www.linux-magazine.com/issue/04/LinuxUSB.pdf
>>>
>>> So it seems that the sidewinder *does* send out buttonpresses when  
>>> the continuous DOF gets near any edge of its range. But when I look  
>>> at the output of evtest, I can see that the button codes for the  
>>> near-edge condition are actually different than the codes for the  
>>> thumb buttons - but I think the [hid] object is mapping the  
>>> different codes to the same output, causing the confusing condition  
>>> that I noticed:
>>>
>>> vertical edge condition: evtest says: 259 (Btn3), [hid] is mapping  
>>> this to the same output as 291 (TopBtn), sending "key btn_3 1" for  
>>> both.
>>> horizontal:  evtest says: 258 (Btn2), [hid] is mapping this to the  
>>> same output as 290 (ThumbBtn2), sending "key btn_2 1" for both.
>>>
>>> So is there a way to ask [hid] to not conflate codes 259/291, and  
>>> 258/290? Or to have [hid] just spit out raw codes, rather than the  
>>> processed textual output that I'm seeing?
>>>
>>> thanks!
>>> -David M.
>>>
>>> David Merrill wrote:
>>>
>>>> Hello Hans, et al -
>>>>
>>>> I've got another puzzling joystick bug that's showing up today as i  
>>>> play around with the [hid] object in linux (Ubuntu Hoary, kernel  
>>>> 2.6.10-5-686).
>>>>
>>>> I am using a Microsoft "Sidewinder Dual Strike" USB joystick, and  
>>>> after changing the permissions on /dev/input/event*
>>>> I can successfully peek at the output with evtest, and I can open  
>>>> the device for reading with the [hid] object.
>>>>
>>>> The strange behavior is that when I push the continuous  
>>>> input-degree-of-freedom near one edge or another, a *button-press*  
>>>> registers, but I have not pressed any button (I see this  
>>>> buttonpress in both evtest, and hans' [hid] external). The  
>>>> continuous DOF of this joystick has a springy region near the edges  
>>>> where there is some resistance - and I get the spurious buttonpress  
>>>> when I cross into this region.
>>>>
>>>> I tried the same joystick in windows, and I don't get the spurious  
>>>> buttonpresses. (I tested it with both the windows control panel  
>>>> "game controllers" interface, and jsarlo's joystick external).
>>>>
>>>> Has anyone see this kind of behavior? Any ideas why it doesn't show  
>>>> up in Windows, but does in Linux? I'd be really interested to find  
>>>> out how to fix something like this..
>>>>
>>>> thanks,
>>>> -David Merrill
>>>>
>>>> Hans-Christoph Steiner wrote:
>>>>
>>>>>
>>>>> On Apr 8, 2005, at 12:11 PM, august wrote:
>>>>>
>>>>>>>> hmm.  I have the 'evdev' module loaded, but there is nothing at
>>>>>>>> /dev/input/event*
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> You need:
>>>>>>>
>>>>>>> mknod /dev/input/event0 c 13 64
>>>>>>> mknod /dev/input/event1 c 13 65
>>>>>>> mknod /dev/input/event2 c 13 66
>>>>>>> mknod /dev/input/event3 c 13 67
>>>>>>> mknod /dev/input/event4 c 13 68
>>>>>>> mknod /dev/input/event5 c 13 69
>>>>>>> ...
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> thanks....I had the devices listed alright....but the permissions  
>>>>>>  weren't
>>>>>> set.  maybe someone else is having the same problem.
>>>>>>
>>>>>> doing "chmod +r /dev/input/event*"  should do the trick.
>>>>>>
>>>>>> now, HID works as expected.....but I only get a resolution from  
>>>>>> 0-255  on
>>>>>> the joystick axis.  Is that how it is supposed to be?   I thought  
>>>>>> the
>>>>>> resolution was much higher.
>>>>>>
>>>>>> best -august.
>>>>>>
>>>>>> _______________________________________________
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>>>>>>
>>>>>
>>>>> "Supposed to" might be the key word there.  That value, AFAIK,  
>>>>> depends  on the hardware.  I have two joysticks: a Logitech  
>>>>> Wingman, which  outputs 0-127, and  a Saitek Force 3D, which  
>>>>> outputs 0-4091.  This is  also why I wrote the [autoscale] object  
>>>>> which is used in the  [joystick], [tablet], and [mouse] objects.   
>>>>> These objects always output  between 0 and 1, converting the  
>>>>> output range of the device, to  resolution between 0 and 1.  Then  
>>>>> when you write a patch for one  joystick, it'll stick work with  
>>>>> other joysticks.
>>>>>
>>>>> .hc
>>>>>
>>>>> ___________________________________________________________________ 
>>>>> _____ ____
>>>>>
>>>>>            "The arc of history bends towards justice."
>>>>>                                                               Dr.   
>>>>> Martin Luther King, Jr.
>>>>>
>>>>>
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>>>>
>>>>
>>>>
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>>
>> ______________________________________________________________________ 
>> ______
>>
>> "Computer science is no more related to the computer than astronomy  
>> is related to the telescope."
>>                                                           -Edsger  
>> Dykstra
>
>
> -- 
> MIT Media Lab
> dmerrill at media.mit.edu
>

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            "The arc of history bends towards justice."
                                            - Dr. Martin Luther King, Jr.

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