User manual

Display Expansion Board - User’s Guide
Page 9
Copyright 2012 © Embedded Artists AB
4 Display Expansion Board Design
This chapter describes the hardware design of the Display Expansion Board. The schematic can be
downloaded from the support page after registering the product serial key (that comes with purchase of
the Display Expansion Board). It can be good to have the schematic side by side when reading this
chapter.
4.1 Block Diagram
The block diagram in Figure 2 below gives a quick overview of a design. It illustrates the major
components in the design.
Figure 2 – The Display Expansion Board Block Diagram
4.2 Schematic Walkthrough
4.2.1 Page 2
J1 is the interface connector to the board. It carries the parallel RGB pixel data as well as control
signals. SPI and I2C serial channels are also present.
The data signals are connected to that TFT5:6:5 and TFT4:4:4 modes of the LPC on-chip LCD
controllers are supported. 24-bit color (TFT8:8:8) depth is supported with some manual wiring, see
section 4.3 below for details.
All high-speed signals have 100 ohm series resistors in order to minimize signal reflections on the
board.
There are three spread spectrum oscillators, 25.175MHz/27MHz/36MHz, which can generate a pixel
clock to the LPC LCD controller. The frequencies have been selected to comply with standard display
settings (VGA/SVGA/480p/576p). There is also one spare position for custom frequency oscillator.
One oscillator at a time is active (output is enabled), which is controlled by U20.
50-pos (2x25) shrouded
IDC connector
I2C-GPIO (PCA9532)
Resistive touch screen controller
(TSC2046) with SPI interface
I2C-E2PROM with
configuration data
TDA19988 HDMI/DVI
transmitter
TFP410 HDMI/DVI
transmitter
Parallel RGB interface (16/12 bit (24 bit with modifications))
+ I2C/SPI bus
I2C
DS90C383BMT
LVDS transmitter
Control signals
SPI
Parallel RGB pixel data
ADV7125KST50 VGA
transmitter
I2C
Oscillators
(25.175/27/36MHz)
Pixel clock