CP316: Microprocessor II

Liquid Crystal Displays (LCDs)

Objectives

Liquid Crystal Displays (LCDs) are a common inexpensive display device. The simple alphanumeric versions are typically based on the Hitachi HD44780 controller standard. As display devices are comparatively slow, time delays are required when interacting with the display. Although the time delays can be executed in software or hardware, you will use hardware timing in this lab.

• using Timer0 as a timer
• using the LCD

Equipment

• HD44780U: LCD-II - Dot Matrix Liquid Crystal Display Controller/Driver [pdf, 60pp; Hitachi]
• Dot Matrix Character LCD Module User's Manual [pdf, 58pp; Optrex Corp.]
• QwikFlash Development Board
• microcomputer with MPLAB IDE and ICD2 installed
  

Procedure

1. Use your program that flashes the left LED every 250 milliseconds (timer0 based program) from the previous lab (question 6). Run the program. Note what you see on the display. The garbage on the display is due to the fact that the LCD was not properly initialized.
   
   
2. Modify your program to include a subroutine to initialize the LCD. When you turn the display on in the last step of the initialization, set cursor on and blink off.
   
   Demonstration - demonstrate and explain your initialization routine
   
   
3. Modify the above program (new project) to alternately display the names of the group members. The names of the group members should be supplied as defined constant strings in program memory. The first names should be on row 1 of the display and the last names should be on row 2 of the display. I suggest that you use subroutines, e.g. to send a command or data to the LCD, to send a null terminated string to the LCD, to clear the LCD.
   
   For example, my program defines data as
   
   name1_f db 0x80,"Nora",0x00
   name1_l db 0xC0,"Znotinas",0x00
   name2_f db 0x80,"Terry",0x00
   name2_l db 0xC0,"Sturtevant",0x00
   
   and my program output alternates between
   
   screen 1: Nora
          Znotinas
   
   screen 2: Terry
          Sturteva
   
   Demonstration - demonstrate and explain the operation of your program
   
   
4. Modify the above program (new project) to write the names of the group members into the LCD buffer (DDRAM). The names of the group members should be supplied as defined constant strings in program memory (as above with a slight modification). Now take the names and continuously scroll them left. For example, my buffer contains:
   
   Nora      Terry
   Znotinas  Sturtevant
   
   After scrolling left 4 times, the display shows:
   
         Te
   inas  St
   
   Demonstration - demonstrate and explain the operation of your program