User manual

Display Expansion Board - User’s Guide

Page 14

 When using the LPC4357 Developer’s Kit together with the Display Expansion Board and

when running SVGA resolution (800x600) at 36MHz, there will be minor flickering on the

HDMI/DVI output from the TDA19988. No flickering has been observed on the output from the

TFP410. It is however likely that the system is running close to the limits.

4.5.3 Limited Driver Functionality for TDA19988

Note that the driver for the TDA19988 has limited functionality. CEC and HDCP are not implemented at

all and all registers are not documented in the available documentation. Contact NXP for further

information about available driver code for the chip. There exists a Linux driver with full functionality

(not provided by Embedded Artists). It is however not a simple task to port this driver to a non-Linux

framework.

Implementing a full HDMI compatible interface is an extensive development effort that is out of the

scope for this Display Expansion Board. The normal procedure is that the source of the display data

negotiates with the monitor about available display formats and then the display source adjust the

picture data to comply with the monitor capabilities. In a typical embedded system with an LPC MCU

there are limited possibilities to adjust the display data. Instead a fixed (commonly used) setting will

always be used.

4.5.4 Picture on Monitors and TV:s

Note that there is no guarantee that pictures can be displayed on tested monitors. The four

selected video standards (VGA/SVGA/480p/576p) are common but not all monitors/TV:s

support them (especially not SVGA with 56Hz frame rate).

4.5.5 Usage - Evaluation

Note that the Display Expansion Board has not been designed for integration into an end-product. It is

for evaluation and prototyping.

4.6 Software Driver

A general software driver has been created to in order to make it simple and non-complex to work with

different displays. This section contains a very brief description of the structure. The code is the

general documentation in itself, simply because the software will likely be updated.

The description below assumes that the LPC1788 Developer’s Kit is used. The software is easily

ported to other kits as well, like the LPC3250 v2, LPC4088 and LPC4357 Developer’s Kits.

The software driver package (a zip-file) is downloaded from Embedded Artists support page for the

Display Expansion Board. The support site is available after registration of the product serial key that

comes with purchase of a Display Expansion Board. The package shall be unzipped in the same

directory as the sample applications for the LPC1788 Developer's Kit. The default name of that

directory is oem_lpc1788. The sample application is called s_display_exp_board.

There is a support library called Lib_Displays. The code in this library contains all low-level details.

The I2C-E2PROM contains configuration information. The I2C address of the memory is 0x56

(1.0.1.0.1.1.0.RW). An application can begin with detecting if an I2C-E2PROM is present on this

address. If so, an Display Expansion Board is attached to the system and the LCD controller and

graphical application can be started.

Some of the parameters are just to copy directly into the LCD controller of the LPC processors. Other

information is stored in readable command strings. The configuration information stored is:

 Magic number to detect that information has been stored.

 Name of LCD and manufacturer in readable strings.

 LCD controller setup, including timing parameters. Can be directly copied to LCD controller

registers.