LCD Test Routine

with user-defined characters and LCD display animation for PIC16F84

Table of Contents [Toc]

Concept
Specifications
Project Resources
Available Microchip PIC Assembler Source Code
Schematics

Concept [Toc] [Top]

This test application demonstrates the usage of the LCD assembler module files for dot matrix LCDs. It works for LCD controllers such as Hitachi HD44780 (PDF data sheet, 389 kB), Samsung KS0073 (PDF data sheet, 673 kB), and compatibles.

It initializes the LCD display to the 4 bit transfer mode, loads two user-defined characters to the CGRAM,
and displays both of them together with some other special characters. Afterwards, an animation using
stars is shown, followed by a forth-and-back shift animation of a 'Hello World' string.

Shows the implementation and functionality of the modules m_wait.asm and m_lcd.asm on the PIC16F84. For the Samsung KS0073 controller type, the constant 'LCDTYPE' must be set to 0x1 to include also the extended function set features for configuration. If this does not help, see also the FAQ section concerning LCD communication issues.

To see a schematic of the connection between LCD and PIC microcontroller, please refer to the schematic section below. Basically, the connection is described in the header section of each LCD assembler module file.

PCB test board for PIC16F84
using a dot matrix LCD display and a MAX232 for RS232 transmission

LCD display after reset
shows two user-defined characters and other special characters of the LCD

LCD display output during operation
shows animation with stars

LCD display output during operation
shows forth-and-back shifting 'Hello World'

Specifications [Toc] [Top]

Processor:	Microchip PIC 16F84
Clock Frequency:	4 MHz crystal (HS mode)
Throughput:	1 MIPS
Code Size of entire Program:	approx. 557 instruction words
LCD Transmission Mode:	4 Bit on D4 - D7 (MSB), uses high nibble of the LCD port
LCD Connections:	7 wires (4 Data, 3 Command)
Total LCD Connections:	10 wires (4 Data, 3 Command, 1 Vdd, 1 GND, 1 Contrast)
Required Hardware:	HD44780 compatible dot matrix LCD (2x16, 2x20 or 2x40 characters)

Project Resources [Toc] [Top]

Available Microchip PIC Assembler Source Code [Toc] [Top]

Main File

HEX Files

Download assembler source code:
LCDx_test.asm

Download Hex File:
LCDx_test.hex

Specifications:
- used module m_lcdx.asm for building HEX-file with portB as LCD port
LCD port connections:
B0: not used, still available for INTB
B1: D4
B2: D5
B3: D6
B4: D7
B5: E
B6: R/W
B7: RS

The above program needs additional include files (modules) to get successfully assembled: m_bank.asm, m_wait.asm, m_lcd.asm

Schematics [Toc] [Top]

Download the PDF schematic to illustrate the connectivity of both 'classes' of LCD driver routines:

Modules m_lcd.asm, m_lcdx.asm, m_lcd_bf.asm, m_lcdxbf.asm: working only on entire ports ([1..7], without [0]),
e.g. PortB[1..7] on PIC16F84,
or PortB[1..7], PortC[1..7], PortD[1..7] on PIC16F77
Modules m_lcde.asm, m_lcde_bf.asm, m_lcdexbf.asm: working on separate, customizable ports,
e.g. PortB[0..2] for control lines & PortA[0..3] for data lines on PIC16F84, PIC16F7x,
or PortC[5..7] for control lines & PortD[0..3] for data lines on PIC16F77, or ...
Note that the data lines have to be on the low nibble of the port.

Last updated: 2005/06/06

[Toc] [Top]