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authorLinus Torvalds <torvalds@g5.osdl.org>2006-06-20 14:49:00 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-06-20 14:49:00 -0700
commitff9144530e9cfe8923e00172e3f8ff83c3b8ff8b (patch)
treec64a9528dde590b9f3174125ad361f46ee30bba8 /Documentation/arm/Sharp-LH/ADC-LH7-Touchscreen
parent25f42b6af09e34c3f92107b36b5aa6edc2fdba2f (diff)
parent96ce2385dd2817da549910001a69ac0a2762a1b9 (diff)
Merge master.kernel.org:/home/rmk/linux-2.6-arm
* master.kernel.org:/home/rmk/linux-2.6-arm: (22 commits) [ARM] 3559/1: S3C2442: core and serial port [ARM] 3557/1: S3C24XX: centralise and cleanup uart registration [ARM] 3558/1: SMDK24XX: LED platform devices [ARM] 3534/1: add spi support to lubbock platform [ARM] 3554/1: ARM: Fix dyntick locking [ARM] 3553/1: S3C24XX: earlier print of cpu idcode info [ARM] 3552/1: S3C24XX: Move VA of GPIO for low-level debug [ARM] 3551/1: S3C24XX: PM code failes to compile with CONFIG_DCACHE_WRITETHROUGH [ARM] 3550/1: OSIRIS: fix serial port map for 1:1 [ARM] 3548/1: Fix the ARMv6 CPU id in compressed/head.S [ARM] 3335/1: Old-abi Thumb sys_syscall broken [ARM] 3467/1: [3/3] Support for Philips PNX4008 platform: defconfig [ARM] 3466/1: [2/3] Support for Philips PNX4008 platform: chip support [ARM] 3465/1: [1/3] Support for Philips PNX4008 platform: headers [ARM] 3407/1: lpd7x: documetation update [ARM] 3406/1: lpd7x: compilation fix for smc91x [ARM] 3405/1: lpd7a40x: CPLD ssp driver [ARM] 3404/1: lpd7a40x: AMBA CLCD support [ARM] 3403/1: lpd7a40x: updated default configurations [ARM] 3402/1: lpd7a40x: serial driver bug fix ...
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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 it's
+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.