[PD] joysticks with hid

[David Merrill]

Hi Chris -

Christian Klippel wrote:

>hi david,
>
>Am Samstag 28 Januar 2006 22:29 schrieb David Merrill:
>  
>
>>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.
>>
>>    
>>
>
>what exactly happens? it sends continous data, and a certain point it also 
>submits a button-press? 
>
yes, that's what happens. there is an invisible threshold at each end of 
the continuous range (imagine thresholds at .1 and .9), and I get an 
'on' when I cross the threshold in one direction, and an off in the other.

>does the continous data continue beyond this point?
>  
>
yes, it's continuous all the way to the end of the mechanical range.

>or is it that there is no continous data at all, and only a button function 
>around that point?
>
>  
>
>>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).
>>
>>    
>>
>
>if they always happen at a certain point, they are not spurious. how does the 
>info for that device look, i.e. what axes and buttons does it have (you can 
>query that with the hid object, afaik....)
>  
>
the email I sent a few minutes ago lists the event codes for button 
presses, and the threshold-crossing 'buttonpresses'.

>  
>
>>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
>>
>>    
>>
>
>it may be that the linux event system gets an certain value wrong. at what 
>continuos data/value does that occur? for example, if it occurs at the 255 - 
>256 crossing, it may be that the 9th bit may be interpreted as a button....
>
>another theory is that the joystick itself send an button event when that 
>boundary is reached, but that windows only shows "regular" buttons, while 
>linux sends whatever comes .... 
>  
>
yeah, I think this is close to what is happening.

>that signal may be used by software to detect when the controller is about to 
>reach its limit soon, but i really dont know.
>  
>
yep, that's what the article says.
-David

>greets,
>
>chris
>
>
>
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