Digi BL1800 user manual R/W pin and DB0-DB3 on

Before running the LCD_DEMO.C sample program, you will need an LCD based on the HD44780 (or an equivalent) controller.

•LCD_DEMO.C—demonstrates a 4-bit interface to an LCD based on the HD44780 (or an equivalent) controller.

Connect the LCD to Parallel Port A.
PA0—LCD DB4	Jackrabbit		Optional Brightness				+5 V	VCC LCD
	Prototyping Board				Control
								VEE
PA1—LCD DB5
						VEE
				10 kW
PA2—LCD DB6	J3
PA3—LCD DB7					-5 V
			PA0					DB4
PA6—LCD RS Register Select	3	4	PA1					DB5
			PA2
								DB6
			PA3
(0 = command, 1 = data)	5	6						DB7
			PA6
PA7—LCD E:normally low, latches								RS
		10	PA7
	9							E
on high to low transition								DB0
								DB1
The R/W pin and DB0–DB3 on								DB2
								DB3
								R/W
the LCD are grounded. DB0–DB3
are not used with a 4-bit interface.

This sample program only involves writing, and that is why we ground the R/W pin. VEE is used to control brightness—the simplest thing to do is ground it. If you need to control the brightness, you can connect a potentiometer between ground and -5 V, with the arm going to the VEE pin. Check the specs on the LCD before doing this as some LCDs may require a different connection. VCC is +5 V and VSS is ground.

User’s Manual 45