[PD-dev] making a libusb object (expanding on [hid] toolkit)

[Hans-Christoph Steiner]

On Jan 21, 2006, at 2:25 AM, Christian Klippel wrote:

> hi,
>
> Am Samstag 21 Januar 2006 06:28 schrieb Mathieu Bouchard:
>> On Fri, 20 Jan 2006, Christian Klippel wrote:
>>> yea, good idea, but impossible to do. you can be sure that whatever
>>> interface you take, it will send its data in a different way.
>>
>> I'm sure that Ben is talking about having a common interface for  
>> things
>> that objects have in common, and not for the things that they don't  
>> have
>> in common. Just because the commonality can't be total doesn't mean it
>> can't exist at all.
>>
>>> each unit has different resolutions, different amounts of i/o, and  
>>> for
>>> that reason, a different protocol.
>>
>> The commonality between objects may be increased by specifying that
>> classes in particular should have a query interface in order to
>> figure out how many sensors there are, how they are labeled if they
>> are labeled, and what is the type and possible values of each sensor.
>>
>
> well, that is what the hid driver (in the os) does already by  
> inspecting the
> report descriptors that the device sent during enumeration.....
> the question is just: is it planned to have, at some time, the [hid]  
> object
> replaced by some more generic objects that use libusb instead and will  
> decode
> this stuff on their own, or will the libusb stuff just an extension to  
> it?

I think this sounds like a good grand plan, but would probably take a  
while to get there.  If there was a USB HID object that received data  
in the Pd space and parsed it into [hid]-style messages, then it could  
be used in combo with a libusb object to replace [hid] in perhaps a  
more flexible way.

>>> this is neccesarry because of the differencies in the devices. it is
>>> even possible that you take two different joysticks, and both pack  
>>> their
>>> messages in completely different ways: one could put all info in just
>>> one report-descriptor, the other may use serveral of them, or even  
>>> one
>>> for each axis/button.
>>
>> Does this happen in practice? Do you have an actual situation where  
>> three
>> joystick models do exactly that?
>>
>
> dont have any joysticks at all. but i have already seen two usb mice  
> that use
> different "data layouts" to send the same information, so there is a
> chance ... altough im sure myself that most devices stick to some kind  
> of
> "common sense" .... well, at least i hope that ....

I have 5 different mice from four different manufacturers and I can say  
that they all work fine with the [mouse] object.   I don't know what is  
going on at the USB level, but I know that the data is coming out of  
the [mouse] object where its supposed to.  The order in which the data  
gets outputted might be different tho.

.hc

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"Computer science is no more related to the computer than astronomy is  
related to the telescope."
                                                           -Edsger  
Dykstra