Hi Guys, I have been working on an expansion board for the BBB that includes a resistive LCD touchscreen. The problem that we are having is that our ESD protection diodes seem to break the break the touch input.
We are using a 4 wire touch interface on AN0, AN1, AN2, and AN3. The symptom we are seeing is that when the diode is connected to the touch interrupt seems to be triggered inconsistently. When checking the signals with a scope, it shows that the interrupt seems to work fine until an application that uses touch is run then it becomes inconsistent. This does not happen if the ESD diode is removed. The apps we are running are the Qt calibration and Qt touch test. Looking at the raw data from the touch device from within Linux on the BBB we see a steady stream of data before a touch app is run, then inconsistent data streams once a touch app is running AND after the app closes. Again this symptom does not happen with the diode removed. My question is 2 parts: 1)What could be happening that would make the touch interrupt inconsistent only when that diode is present AND one of these applications is run? 2) Do we really need additional ESD protection? Does Anyone have any experience with a BBB and a heavy usage resistive touch screen, that is not have additional ESD protection? In the two cape examples I looked at additional ESD protection is not used. This is the ESD part that we are using: http://www.comchiptech.com/cms/UserFiles/CPDT6-5V4U%20RevD364097.pdf Thanks Cyril -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
