Troubleshooting Touch Panels
If you're having trouble with your touch panel, here are some tips and tests for determining where the problem lies.
Symptoms
The following are some of the more common touch panel problems you might encounter along with the relevant sections to check.
Can't get past calibration screen: cable, aging touch panel
Touch panel doesn't respond: cable, software settings
Calibration drifts over a short period of time: cable, aging touch panel
Difficult to double-tap: timing
Tests
Try dragging the stylus diagonally across the CE desktop. This will draw a box on the screen. If the edge jumps around more than a pixel or two, may have noise in your touch panel. You can test for calibration drift by noting how closely the edge of the box tracks to your stylus.
Probe with an oscilloscope at the ADS board's touch panel connector. When you hold a stylus to the touch panel, you should see a series of pulses on each of the connector pins (if you don't, there may be a break in the cable). Move your finger in the X or Y directions. You should see the voltage level of the pulses change.
Solutions
Touch panel problems can occur in the hardware (cable, touch panel or board defects), integration (esp. cable length) and the software (primarily driver timing).
Cabling
The most common failure point for touch panels is the cabling. Failure points include the connector crimp onto the touch panel's flat flex connector and crimps on the cables from the touch panel to the ADS board.
Worn out Touch Panel
The second most common point of failure is the touch panel surface itself. Touch panels do wear out; five-wire touch panels last longer than four- and eight-wire touch panels. You will prolong the life of your touch panel if you use finger or stylus; tips of pens, tweezers, screwdrivers are touch panel killers.
Software Drivers
ADS creates touch panel drivers for the touch panel installed on your system. Sometimes your application's environment doesn't match ADS' laboratory conditions. If this is the case, ADS may be able to tune the touch panel driver settings to better meet your application needs.
Software Settings
Operating systems typically allow you to disable the touch panel driver (eg. Win CE, Linux). While this is not a common point of failure, it's included in this list for completeness.
For further reading about touch panels on ADS products, see the touch panel topic index.
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Drew Kidder
ADS Technology Transfer
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Posted - 01 Nov 2002 : 18:09:45
