[PD] joysticks with hid

David Merrill dmerrill at media.mit.edu
Sun Jan 29 04:57:36 CET 2006 

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! :)

>
> 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] ?
-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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