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PDF AN2356 Data sheet ( Hoja de datos )
| Número de pieza | AN2356 | |
| Descripción | Graphics Library | |
| Fabricantes | Cypress | |
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Application Note
AN2356
Graphics Library for OSRAM’s OLED Displays
www.DataSheet4U.com
Author: Valeriy Kyrynyuk
Associated Project: Yes
Associated Part Family: All
PSoC Designer Version: 4.2
Associated Application Notes: AN2348
Abstract
This Application Note describes a graphics library for OLED display operation. Library functions
include drawing, text, and bitmap operations.
Introduction
Modern designs often require a low-cost and high
quality graphical display. OLED (organic light
emitting diode) displays by OSRAM Opto
Semiconductors (http://www.pictiva.com) meet
these requirements and are the preferred
displays for users and designers. This Application
Note describes a library of functions to interface
with a display that has a resolution of 96 x 48
pixels.
OLED Review
OSRAM OLED displays have the following
characteristics:
o They are monochrome and have 16
brightness levels.
o The interface supply voltage is 2.4-3.5V.
o The OLED supply voltage is 12-13V.
o The operating temperature range is
between -30°C and 70°C.
o They have low power consumption at
220 mW maximum (OLED supply).
o No additional lighting elements are
required.
o Lifetime at standard brightness is
between 10 000 - 40 000 hours.
o Parallel or serial (SPI) are the standard
interface options.
Consider the display process in detail. An OLED
display is a memory-mapped device. Four bits
are necessary to display one pixel, because an
OLED display has 16 brightness levels of one
basic color; a single byte can hold information for
two pixels. The columns and rows of the display
can serve as the X and Y axes, respectively. One
byte in video memory represents two pixels in the
X direction. Therefore, to simplify algorithms for
the display of images, the X coordinates of
function arguments are assigned as one half of
the real pixel position in its row. The pixel
representation in a video memory byte is shown
in Figure 1.
X X +1
4..7 bits 0..3 bits
Figure 1. Video Memory Byte Format
Interfacing with PSoC®
The demonstration board is implemented using a
CY8C29666 PSoC device. The interconnection
circuit is shown in Figure 2. The connection is
done by parallel interface. For a detailed
description of this interface, refer to reference [1]
from Solomon Systech Company at the end of
this document. The maximum logic supply
voltage of the display is 3.5V.
3/16/2006
Revision A
-1-
1 page  
AN2356
Implementation of Fonts
The most important task for the display driver is
to display text information. Two font types/sizes
are implemented in the library. The range of their
symbols is from 0x20 to 0x7F of the ASCII table.
The size of the small font is 5x8 pixels and the
large font is 8x16 (see Figure 4 (B)).
The bit images for each symbol of the small font
are located in the small_font.h file. The bit
images for the large font are located in the
big_font.h file.
www.DataSheet4U.com
(A)
(B)
Figure 4. Large and Small Fonts
(A) “Negative” Mode
(B) “Positive” Mode
The font symbol is represented as an array of
bytes that hold the monochrome image of each
symbol (see Figure 5).
Small Font
Bit
01 h
02 h
04 h
08 h
10 h
20 h
40 h
80 h
01234
Large Font
Bit
01h
02h
04h
08h
10h
20h
40h
80h
01h
02h
04h
08h
10h
20h
40h
80h
0 1 2 3 45 6 7
Figure 5. Format of Symbol Bitmap Image
As we can see, a symbol in the small font needs
5 bytes for implementation, and a symbol in the
large font needs 14 bytes. Both the high-level
functions for working with fonts were previously
described. The program Fontbuilder.exe allows
custom fonts to be built and is included with the
project.
OLED Recommendations
Reducing pixel emission time and brightness are
particularly useful ways to extend the lifetime of
OLED displays. Users should also avoid using
“Positive” (B) Screen Mode (Figure 4). For
detailed information about optimizing the display
operation, see reference [4] “Effective Use of
Pictiva™ OLED Displays: Power, Image and
Lifetime Optimization.” To include screen savers
in OLED projects, refer to reference [5] “OLED
Display Module Screen Saver.”
An OLED display requires a regulated power
supply of +12V. There are many ways to
generate this voltage supply. The demonstration
project discussed in this Application Note uses a
step-up converter to transform +3.3V to +12V.
This converter only uses hardware resources of
the PSoC: one switched capacitor block (analog
comparator), two digital blocks (PWM and
DigBuf), and one row LUT. The operation
principle is the same as with the switch mode
pump. The step-up converter is controlled by
enabling\disabling the PWM output. The PWM
duty cycle is set to (1− 3.3V ) ×100% = 72.5% to
12V
provide optimal converter operation.
3/16/2006
Revision A
-5-
5 Page | ||
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