• DRIVERS
• POSITIONING CHARACTERS ON THE DISPLAY
• NOTES

LCD_LF.ZIP (LogicFlex single board computer and LogicFlex-EPX control system), LCD_EX.ZIP (Flashlite 386Ex single-board computer) and LCD.ZIP (Flashlite-V25 single-board computer) are drivers for one or two LCD's connected to the Flashlite's J7 (386Ex) or J5 (V25) port. The driver supports standard alpha-numeric LCD displays using the Hitachi HD44780A controller chip. Data sent to LPT1 or 2 is re-directed to the LCD displays. Documentation and source code is included along with a demo application in Quickbasic.

A table of position codes is shown below. Use these codes to put a character at a specific location. The values are given in decimal and in hex.

For Example, when using our LCD driver, the following basic program will initialize a 4x20 LCD and print a test message on lines 3 and 4 starting in the 13th column of the display.

open "lpt1" for output as #1    ' set up LPT1 for output
print #1,chr$(160);chr$(40);    ' 4 bits, 4 lines, 5x7 matrix
print #1,chr$(160);chr$(12);    ' display on, cursor and blink off
print #1,chr$(160);chr$(6);     ' increment cursor, no display shift
print #1,chr$(160);chr$(1);     ' clear and home display
  
print #1,chr$(160);chr$(&hA0);  ' position cursor at line 3, row 13
print #1,"HELLO"                ' output text on LCD
print #1,chr$(160);chr$(224);   ' position cursor at line 4, row 13
print #1,"WORLD"                ' output text on LCD

In the above example, the 160 is a command byte sent to the LCD driver. This must be sent as a byte, not as the characters 1, 6, and 0.

When using a 4x20 display, it is important remember that the LCD has 2 control chips. One chip displays information on lines 1 and 3 of the LCD, the other displays information on lines 2 and 4.

Most of the problems we encounter with LCDs are due to incorrect wiring. Carefully verify the wiring between the JK microsystems embedded computer and the LCD if you have trouble.

Although our LCDs will function with the contrast pin tied to ground, the contrast might not be the best for a given viewing angle. To adjust the contrast, install a 10k potentiometer between VCC and ground and connect the wiper to pin 3 of the LCD. Be sure the ground connection is at Pin 1.

See our C programming page for more examples.