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authorMarc Singer <elf@buici.com>2006-05-16 06:41:43 -0400
committerRussell King <rmk+kernel@arm.linux.org.uk>2006-06-18 11:16:51 -0400
commit51cb21a9cd2e3bba8a69948794eb9480facdef45 (patch)
treefde0724d77635c2f4c681b9f35b07e17314b6cf5 /Documentation/arm
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>
Diffstat (limited to 'Documentation/arm')
-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
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index 00000000000..1e6a23fdf2f
--- /dev/null
+++ b/Documentation/arm/Sharp-LH/ADC-LH7-Touchscreen
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1README on the ADC/Touchscreen Controller
2========================================
3
4The LH79524 and LH7A404 include a built-in Analog to Digital
5controller (ADC) that is used to process input from a touchscreen.
6The driver only implements a four-wire touch panel protocol.
7
8The touchscreen driver is maintenance free except for the pen-down or
9touch threshold. Some resistive displays and board combinations may
10require tuning of this threshold. The driver exposes some of it's
11internal state in the sys filesystem. If the kernel is configured
12with it, CONFIG_SYSFS, and sysfs is mounted at /sys, there will be a
13directory
14
15 /sys/devices/platform/adc-lh7.0
16
17containing these files.
18
19 -r--r--r-- 1 root root 4096 Jan 1 00:00 samples
20 -rw-r--r-- 1 root root 4096 Jan 1 00:00 threshold
21 -r--r--r-- 1 root root 4096 Jan 1 00:00 threshold_range
22
23The threshold is the current touch threshold. It defaults to 750 on
24most targets.
25
26 # cat threshold
27 750
28
29The threshold_range contains the range of valid values for the
30threshold. Values outside of this range will be silently ignored.
31
32 # cat threshold_range
33 0 1023
34
35To change the threshold, write a value to the threshold file.
36
37 # echo 500 > threshold
38 # cat threshold
39 500
40
41The samples file contains the most recently sampled values from the
42ADC. There are 12. Below are typical of the last sampled values when
43the pen has been released. The first two and last two samples are for
44detecting whether or not the pen is down. The third through sixth are
45X coordinate samples. The seventh through tenth are Y coordinate
46samples.
47
48 # cat samples
49 1023 1023 0 0 0 0 530 529 530 529 1023 1023
50
51To determine a reasonable threshold, press on the touch panel with an
52appropriate stylus and read the values from samples.
53
54 # cat samples
55 1023 676 92 103 101 102 855 919 922 922 1023 679
56
57The first and eleventh samples are discarded. Thus, the important
58values are the second and twelfth which are used to determine if the
59pen is down. When both are below the threshold, the driver registers
60that the pen is down. When either is above the threshold, it
61registers 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
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+++ b/Documentation/arm/Sharp-LH/LCDPanels
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1README on the LCD Panels
2========================
3
4Configuration options for several LCD panels, available from Logic PD,
5are included in the kernel source. This README will help you
6understand the configuration data and give you some guidance for
7adding support for other panels if you wish.
8
9
10lcd-panels.h
11------------
12
13There is no way, at present, to detect which panel is attached to the
14system at runtime. Thus the kernel configuration is static. The file
15arch/arm/mach-ld7a40x/lcd-panels.h (or similar) defines all of the
16panel specific parameters.
17
18It should be possible for this data to be shared among several device
19families. The current layout may be insufficiently general, but it is
20amenable to improvement.
21
22
23PIXEL_CLOCK
24-----------
25
26The panel data sheets will give a range of acceptable pixel clocks.
27The fundamental LCDCLK input frequency is divided down by a PCD
28constant in field '.tim2'. It may happen that it is impossible to set
29the pixel clock within this range. A clock which is too slow will
30tend to flicker. For the highest quality image, set the clock as high
31as possible.
32
33
34MARGINS
35-------
36
37These values may be difficult to glean from the panel data sheet. In
38the case of the Sharp panels, the upper margin is explicitly called
39out as a specific number of lines from the top of the frame. The
40other values may not matter as much as the panels tend to
41automatically center the image.
42
43
44Sync Sense
45----------
46
47The sense of the hsync and vsync pulses may be called out in the data
48sheet. On one panel, the sense of these pulses determine the height
49of the visible region on the panel. Most of the Sharp panels use
50negative sense sync pulses set by the TIM2_IHS and TIM2_IVS bits in
51'.tim2'.
52
53
54Pel Layout
55----------
56
57The Sharp color TFT panels are all configured for 16 bit direct color
58modes. The amba-lcd driver sets the pel mode to 565 for 5 bits of
59each red and blue and 6 bits of green.