Non-finger detection, baseline removal, and power adapters

This topic provides notes for multi-touch hardware solutions on non-finger detection, baseline removal, and power adapters.

Non-finger detection

A non-finger is defined as a component that is likely not a finger due to its size and shape, as well as the distribution of its sensor pixel values.

A non-finger can be detected through certain approaches. A simple approach is to use a certain set of heuristic tests such as area test, shape test, fractional dimension test, and so on.

Non-finger detection can also be used to report the touch as palm with the palm indicator set.

Failure Cases:

  • Massive interference with all scenarios – causes non-fingers to be interpreted as finger touches.

  • Baseline removal – failure to identify a non-finger can lose the chance to promptly update the baseline, resulting in sub-optimal balance between the sensitivity and ghost reports.

Baseline removal

Properly and promptly identify the baseline case within a short time that such updating will not interfere with user attention of baseline change and remove it immediately.

Related Issues:

  • Sub-optimal balance of sensitivity and ghost reports.

Power adapters

Different power adapters can generate different noise levels that impact touch performance. Each unique power adaptor configuration should be considered as a unique touch device. Thus if the same touch device is shipped with two different power modules (for example, 2 pins or 3 pins for different regions), each should be considered as a unique touch device.

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