K51-AVR 5 of 7 EXPERIMENTAL CARD FOR 8051 AND AVR MICROPROCESSORS FAMILY

Salvatore Damino

In this article we examine the features and the hardware interface and software drive modalities of LCD Display.

ALPHANUMERIC LCD DISPLAY

The LCD Display is frequently used, in several way and types, every time there is the necessity to represent any information. Three most important reasons of its succes are: cheaper tecnology, smaller energy request and its comfort use.

GENERAL FEATURES

LCD Alfanumerical Displays are inteligent devices driven through a simple parallel BUS, 4 or 8 bit width.
On the figure number 1 you can see the hardware interface modality between a LCD Display and CPU with 4 or 8 bits.
Instead figure 2 show the initialization flow chart for LCD Display with 4 or 8 bits interface.
Every LCD Display according to manufacturing company, has an own characters set. It's composed by standard alphabet, either capital and small. Letters numbers and some grafic symbols. There are all the European symbols dedicated to accent letters, cedillas, etc., and finally there are free grafic symbols that change from producer to producer.
On the figure number 3 you can see the complete set of 256 characters, in a modern LCD Alfanumerical Display.
Some Displays, not for European market, have a Japanese caracters set.

SELECTION LCD DISPLAY

Who has to choose an LCD Display must carefully consider the information above described. For example if the application requires only the ASCII code representation, every LCD Display is right, but if, we have to represent an accent E or U we have to write German messages or in different languages (I.E. the Spanish ? reversed), there are unusual letters, and we could have some problems. First problem is that there isn't the required letter. Second: there is the letter but in different place inside characters table. Both cases are hard.

At the end of this short explanation on the modality to make a right choice of LCD Display I hope that you have enought elements to chose the right one.

DISPLAY CONNECTION

As you can see, from electric diagram, on figure 4 for the connection of LCD Display to K51 - AVR are sufficent10 wires.
Two are for power supply; one for E signal, one for RS signal, four for BUS data, one for possible LED back light; and one for brightnes regulation.
More simple is the software management. Bascom compiler has a list of specific commands for external devices driving as I2C - BUS; infrared receivers for remote - control etc. Between thee severals devices there are also comfortables LCD Displays.
As you can observe from the program source, directly available on grifo® web site, once assigned the correspondence between microcontroller pins and Display signals, remain the driving.
It doesen't matter the knowledge of signals sequence describe on first tables. Powerful BASCOM compiler make all alone and in a simple and efficent way.

Data Sheets:

- Interfacing between LCD Display and CPU of 4 or 8 bit,

- Inizialization of Display throw CPU of 4 or 8 bit,

- Table complete with a map of 256 characters,

- Screw terminal connector for LCD Display and trimmer for brightness.

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Page up-dated at August 29, 2004

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