On Wed, 7 Aug 2002 15:20:40 -0500 Carl Wilhelm Soderstrom <[EMAIL PROTECTED]>wrote:
> I know that there are regular posts from touchscreen driver-writers to this > list; so I'd like to know if there's any hope of supporting a particular > model. > > this device: > http://www.xploretech.com/genesys/genesys.html > > says it has a: > "Touch Screen 5-wire, resistive analog touch screen" > > how do these things usually interface with XFree86? I don't suppose it's > likely to be as simple as appearing to be a PS/2 device, is it? > > are there any suggestions for touchscreen devices, that work with XFree86? > We haven't yet bought any hardware; this is just one device that's under > strong consideration. I wrote a driver for the ViewSonic ViewPad 1000 touchscreen. From that experience I know you don't have, or haven't provided, enough information to tell what will work. The key is that Xplore only describes the type of touchscreen used, not how it is interfaced to the system. The ViewPad uses the Semtech Screencoder interface chip. It is connected between the traditional pointing device and the computer. It captures and reformats PS/2 or Intellimouse PS/2 or Explorer PS/2 packets from the traditional pointing device, while injecting its own packets caused by touchscreen activity. In default mode, all touchscreen activity generates relative mouse motion--think of it as a very large touchpad. My driver changes mode so that the touchscreen generates absolute position packets, then snatches those packets from the data stream and tells X where to put the pointer. The key to my success was getting ViewSonic and Semtech to provide sufficient technical information. I don't believe than any amount of probing would have exposed what chip is used and how it worked. If the GeneSys uses this chip, your effort should be small. If not, you'll have to go through a comparable effort--the greater part of which is getting the technical information. I should mention in passing that I've heard of at least one other display which uses this chip, and my driver seems to work for it. Folks using that device have developed calibration utilities, etc., but I found that a common fixed calibration (in XF86Conf-4 file) is sufficient for the several dozen ViewPads we have. I've considered adding run-time calibration support, and some kind of polynomial interpolation routine to deal with non-linear tracking, but neither have proven necessary. Our users use their fingers to press buttons which are displayed on the screen, so an error of a few pixels is not critical. Nevertheless, much of the foundation is present should it be needed. Randolph Bentson [EMAIL PROTECTED] _______________________________________________ Xpert mailing list [EMAIL PROTECTED] http://XFree86.Org/mailman/listinfo/xpert
