LCD INTERFACING WITH PARALLEL PORT
This tutorial is taken from the book MY EXPERIENCE IN PARALLEL PORT INTERFACING. you can download it free from the files section(file:-parallelport(3 files) of yahoo group-booksbybibin http://groups.yahoo.com/group/booksbybibin/ comments about this book on www.booksbybibin.blogspot.com LCD DISPLAY Here I am using a 16X2 LCD display available for around Rs.140. The LCD JHD162A More tutorials about LCD is available on the following links http://www.roboticsindia.com/modules.php?name=News&file=print&sid=75 http://www.beyondlogic.org/parlcd/parlcd.htm http://www.eio.com/lcdintro.htm http://home.iae.nl/users/pouweha/lcd/lcd0.shtml#hd44780 http://ee.cleversoul.com/lcd_project.html See the commands from the first link and see the program. #include"bparlib.c" #define Set_Enable Set_ControlPort_bit(2) #define Clear_Enable Clear_ControlPort_bit(2) #define Write_Lcd Clear_ControlPort_bit(1) #define Read_Lcd Set_ControlPort_bit(1) #define Select_InstructionRegister Clear_ControlPort_bit(0) #define Select_DataRegister Set_ControlPort_bit(0) #define Data_Lcd(a) Write_DataPort(a) void main() { char string[] = {"BIBIN JOHN"}; char init[10]; int len,i; init[0] = 0x01; /* Init Display */ init[1] = 0x38; /* Clear Display */ init[2] = 0x0c; /* Dual Line / 8 Bits */ init[3] = 0x06; init[4] = 0x80; /*clearing all bits of control port*/ for(i=0;i<4;i++) Clear_ControlPort_bit(i); Select_InstructionRegister; for(i=0;i<5;i++) { Data_Lcd(init[i]); Set_Enable; delay(30); Clear_Enable; delay(30); } Select_DataRegister; len=strlen(string); for (i=0; i< len;i++) { Data_Lcd(string[i]); Set_Enable; delay(30); Clear_Enable; delay(30); } } first select the instruction register to write these following commands. See the table of commands init<0> = 0x01; init<1> = 0x38; init<2> = 0x0c; init<3> = 0x06; init<4> = 0x80; 0x01 is used to clear display 0x38 for 2 lines and 8 bits 0x0c 0x06 0x80 is the CRA Address Corresponds to the cursor address. This is the main thing you should do first Now select the data register and write the data you want to send. Delays should be proper for the display to set. The following program writes some data into the LCD which will remain stored in the RAM of LCD TROUBLESHOOTING: 1. Make the LCD ON by varying the contrast. You vary the potentiometer knob so that the contrast will vary and you will get dark matrix on the screen. 2. Reduce the contrast so that dark dot's of less intensity will be seen. 3. Now run the program, check for parallel port troubleshooting. 4. The delay inserted in the program should be sufficient. 5. The CRA address should be correct.