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authorMarc Singer <elf@buici.com>2006-05-16 11:41:43 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2006-06-18 16:16:51 +0100
commit51cb21a9cd2e3bba8a69948794eb9480facdef45 (patch)
treefde0724d77635c2f4c681b9f35b07e17314b6cf5
parentd4adcffb6574d3414f2e39d6ca1be5eccf97ac52 (diff)
[ARM] 3407/1: lpd7x: documetation update
Patch from Marc Singer New documentation for the touchscreen controllers and LCD panels. Signed-off-by: Marc Singer <elf@buici.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
-rw-r--r--Documentation/arm/Sharp-LH/ADC-LH7-Touchscreen61
-rw-r--r--Documentation/arm/Sharp-LH/LCDPanels59
2 files changed, 120 insertions, 0 deletions
diff --git a/Documentation/arm/Sharp-LH/ADC-LH7-Touchscreen b/Documentation/arm/Sharp-LH/ADC-LH7-Touchscreen
new file mode 100644
index 00000000000..1e6a23fdf2f
--- /dev/null
+++ b/Documentation/arm/Sharp-LH/ADC-LH7-Touchscreen
@@ -0,0 +1,61 @@
+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.
diff --git a/Documentation/arm/Sharp-LH/LCDPanels b/Documentation/arm/Sharp-LH/LCDPanels
new file mode 100644
index 00000000000..fb1b21c2f2f
--- /dev/null
+++ b/Documentation/arm/Sharp-LH/LCDPanels
@@ -0,0 +1,59 @@
+README on the LCD Panels
+========================
+
+Configuration options for several LCD panels, available from Logic PD,
+are included in the kernel source. This README will help you
+understand the configuration data and give you some guidance for
+adding support for other panels if you wish.
+
+
+lcd-panels.h
+------------
+
+There is no way, at present, to detect which panel is attached to the
+system at runtime. Thus the kernel configuration is static. The file
+arch/arm/mach-ld7a40x/lcd-panels.h (or similar) defines all of the
+panel specific parameters.
+
+It should be possible for this data to be shared among several device
+families. The current layout may be insufficiently general, but it is
+amenable to improvement.
+
+
+PIXEL_CLOCK
+-----------
+
+The panel data sheets will give a range of acceptable pixel clocks.
+The fundamental LCDCLK input frequency is divided down by a PCD
+constant in field '.tim2'. It may happen that it is impossible to set
+the pixel clock within this range. A clock which is too slow will
+tend to flicker. For the highest quality image, set the clock as high
+as possible.
+
+
+MARGINS
+-------
+
+These values may be difficult to glean from the panel data sheet. In
+the case of the Sharp panels, the upper margin is explicitly called
+out as a specific number of lines from the top of the frame. The
+other values may not matter as much as the panels tend to
+automatically center the image.
+
+
+Sync Sense
+----------
+
+The sense of the hsync and vsync pulses may be called out in the data
+sheet. On one panel, the sense of these pulses determine the height
+of the visible region on the panel. Most of the Sharp panels use
+negative sense sync pulses set by the TIM2_IHS and TIM2_IVS bits in
+'.tim2'.
+
+
+Pel Layout
+----------
+
+The Sharp color TFT panels are all configured for 16 bit direct color
+modes. The amba-lcd driver sets the pel mode to 565 for 5 bits of
+each red and blue and 6 bits of green.