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-README on the ADC/Touchscreen Controller
-========================================
-
-The LH79524 and LH7A404 include a built-in Analog to Digital
-controller (ADC) that is used to process input from a touchscreen.
-The driver only implements a four-wire touch panel protocol.
-
-The touchscreen driver is maintenance free except for the pen-down or
-touch threshold. Some resistive displays and board combinations may
-require tuning of this threshold. The driver exposes some of its
-internal state in the sys filesystem. If the kernel is configured
-with it, CONFIG_SYSFS, and sysfs is mounted at /sys, there will be a
-directory
-
- /sys/devices/platform/adc-lh7.0
-
-containing these files.
-
- -r--r--r-- 1 root root 4096 Jan 1 00:00 samples
- -rw-r--r-- 1 root root 4096 Jan 1 00:00 threshold
- -r--r--r-- 1 root root 4096 Jan 1 00:00 threshold_range
-
-The threshold is the current touch threshold. It defaults to 750 on
-most targets.
-
- # cat threshold
- 750
-
-The threshold_range contains the range of valid values for the
-threshold. Values outside of this range will be silently ignored.
-
- # cat threshold_range
- 0 1023
-
-To change the threshold, write a value to the threshold file.
-
- # echo 500 > threshold
- # cat threshold
- 500
-
-The samples file contains the most recently sampled values from the
-ADC. There are 12. Below are typical of the last sampled values when
-the pen has been released. The first two and last two samples are for
-detecting whether or not the pen is down. The third through sixth are
-X coordinate samples. The seventh through tenth are Y coordinate
-samples.
-
- # cat samples
- 1023 1023 0 0 0 0 530 529 530 529 1023 1023
-
-To determine a reasonable threshold, press on the touch panel with an
-appropriate stylus and read the values from samples.
-
- # cat samples
- 1023 676 92 103 101 102 855 919 922 922 1023 679
-
-The first and eleventh samples are discarded. Thus, the important
-values are the second and twelfth which are used to determine if the
-pen is down. When both are below the threshold, the driver registers
-that the pen is down. When either is above the threshold, it
-registers then pen is up.