![](http://datasheet.mmic.net.cn/260000/PPSMMANUAL_datasheet_15946768/PPSMMANUAL_30.png)
6-2
Using Using Graphics Tools
Programmer’s Manual
6.1
Display Screen Format
Figure 6-1shows the general screen architecture for the PPSM system. There are
three major areas:
Pen Input Area
LCD Display Screen
Panning Display Screen
6.1.1
LCD Display Screen
The Display Screen is the region of the LCD display where applications can
display output data. Its size will depend on manufacturer, e.g. 320 pixels wide by
200 pixels high or 320 pixels wide by 240 pixels high, etc.
The LCD module is capable of 1 bit per pixel or 2 bits per pixel output, giving 2
grey levels or 4 grey levels respectively. Hence, there are WHITE and BLACoutside the LCD display region, the display coordinate returned may be negative
1 bit per pixel and WHITE, LIGHT_GREY, DARK_GREY and BLACK for 2 bitsor even greater than the display screen size.
Figure 6-1 Generic Screen Format
LCD Display Panel
Origin (0,0)
Negative Coordinates
Positive Coordinates
Touch Panel
Personal Portable System Manager
Programmer’s Manual
6-3
pixel.
The reference coordinate point for the LCD Display Screen is at the top left
corner, the Display Origin. This has the values of (0, 0) initially. Coordinates
associated with the LCD Screen are referred to as the display coordinates.
6.1.2
Panning Display Screen
The Panning Screen is an extension to the LCD Display Screen. Its main purpose
is to allow applications to write data to an area outside of the actual display area.
Although applications can write to this area, data will not be displayed on the
screen unless this area is being mapped to the LCD Display Screen. Pen Input
areas on the panning screen will receive pen input data only when they overlap
with the LCD display screen.
Panning Screen has a similar coordinate system as the LCD Display Screen with
different origin. It is configurable but limited by the following:
The maximum memory size for a panning screen is limited to 64K
byte.
In 1 bit per pixel mode, the width of the panning screen must be
divisible by 16 and limited to a maximum of 4096 pixels. In 2 bits
per pixel mode, the width must be divisible by 8 and limited to a
maximum of 2048 pixels.
The height of the display is only limited by the amount of memory
that is available for a given width.
6.2
Screen Initialization
Because every hardware system will not be identical, a screen initialization
procedure is required when PPSM is first activated. This is essential for the
calibration of the alignment between the pen input device and LCD display
screen.
Screen initialization is implemented when PPSMInit() is called.
Example 6-1 Initialize screen through PPSMInit()
57
58
main()
{
.
.
.
/* Initialize PPSM with pen calibration */
PPSMInit(TRUE);
62
63
The touch panel can be larger than the LCD Display Screen. However, the PPSM
tools will only return LCD display screen coordinate. When a pen is touching
F
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
n
.