LCD interfacing with AVR microcontroller
This tutorial is taken from the book MY EXPERIENCE IN PROGRAMMING AVR MICROCONTROLLER IN C USING WINAVR/AVRGCC. you can download it free from the files section(FILE-AVRBOOK.RAR) of yahoo group-booksbybibin http://groups.yahoo.com/group/booksbybibin/ comments about this book on www.booksbybibin.blogspot.com INTERFACING LCD WITH AVR LCD used: JHD162A This is the simple schematic without using backlight and contrast pins. Here control pins are connected to PORTD and datapins to PORTA. See the figure below. /*---------------------------------------------------------------- -----------------HEADER FILES------------------------------------- -----------------------------------------------------------------*/ #include<avr/io.h> /*---------------------------------------------------------------- -------------CONNECTION BETWEEN LCD AND ATMEGA32----------------- -----------------------------------------------------------------*/ #define DATA_DDR DDRA #define DATA_PORT PORTA #define CONTROL_DDR DDRD #define CONTROL_PORT PORTD #define Enable_Pin 6 #define RegSelect_Pin 4 #define ReadWrite_Pin 5 #define CONTROL_MASK 0X70 /*---------------------------------------------------------------- -------------CONTROL BITS OF LCD -------------------------------- -----------------------------------------------------------------*/ #define Set_Enable CONTROL_PORT|=_BV(Enable_Pin) #define Clear_Enable CONTROL_PORT&=~_BV(Enable_Pin) #define Write_Lcd CONTROL_PORT&=~_BV(ReadWrite_Pin) #define Read_Lcd CONTROL_PORT|=_BV(ReadWrite_Pin) #define Select_InstructionRegister CONTROL_PORT&=~_BV(RegSelect_Pin) #define Select_DataRegister CONTROL_PORT|=_BV(RegSelect_Pin) #define Data_Lcd(a) DATA_PORT=a #define delay(a) delay_ms(a) /*---------------------------------------------------------------- -----------------FUNCTIONS--------------------------------------- -----------------------------------------------------------------*/ void Init_Ports(void); void Init_Lcd(void); void delay_ms(unsigned char time_ms); void Lcd_Send(unsigned char a); /*---------------------------------------------------------------- ----------------MAIN FUNCTION-------------------------------------- -----------------------------------------------------------------*/ void main() { int len,i; char string[] = {'B','I','B','I','N',' ','J','O','H','N'}; Init_Ports(); Init_Lcd(); len=10; for (i=0; i< len;i++) Lcd_Send(string[i]); } /*---------------------------------------------------------------- -----------------SEND A CHARACTER TO LCD------------------------- -----------------------------------------------------------------*/ void Lcd_Send(unsigned char a) { Select_DataRegister; Write_Lcd; Data_Lcd(a); Set_Enable; delay(30); Clear_Enable; delay(30); } /*---------------------------------------------------------------- -----------------FUNCTIONS TO INITIALIZE PORTS-------------------- -----------------------------------------------------------------*/ void Init_Ports(void) { DATA_DDR=0XFF; //Setting data port for output CONTROL_DDR=CONTROL_MASK;//setting selected pins of control port for output CONTROL_PORT&=~(_BV(Enable_Pin)|_BV(RegSelect_Pin )|_BV(ReadWrite_Pin)); //setting values to 0 at starting } /*---------------------------------------------------------------- ------------FUNCTION TO INITIATE LCD ----------------------------- -----------------------------------------------------------------*/ void Init_Lcd(void) { char init[10]; int i; init[0] = 0x01; init[1] = 0x38; init[2] = 0x0c; init[3] = 0x06; init[4] = 0x80; Select_InstructionRegister; Write_Lcd; for(i=0;i<5;i++) { Data_Lcd(init[i]); Set_Enable; delay(30); Clear_Enable; delay(30); } } /*---------------------------------------------------------------- --------FUNCTION TO GENERATE DELAY IN MILLISECONDS---------------- -----------------------------------------------------------------*/ void delay_ms(unsigned char time_ms) { unsigned short delay_count = F_CPU / 400; unsigned short cnt; asm volatile ("\n" "L_dl1%=:\n\t" "mov %A0, %A2\n\t" "mov %B0, %B2\n" "L_dl2%=:\n\t" "sbiw %A0, 1\n\t" "brne L_dl2%=\n\t" "dec %1\n\t" "brne L_dl1%=\n\t":"=&w" (cnt) :"r"(time_ms), "r"((unsigned short) (delay_count)) ); } Folder:lcd(yahoo group-booksbybibin, file-avrbook.rar) /*---------------------------------------------------------------- -------------CONNECTION BETWEEN LCD AND ATMEGA32----------------- -----------------------------------------------------------------*/ #define DATA_DDR DDRA #define DATA_PORT PORTA #define CONTROL_DDR DDRD #define CONTROL_PORT PORTD #define Enable_Pin 6 #define RegSelect_Pin 4 #define ReadWrite_Pin 5 #define CONTROL_MASK 0X70 Here are the declaration I am using. Here CONTROL_MASK is used so that remaining pins can be used for other purpose. Change the port settings here so that you can use same code for all ports. When you program you should program in such a way that port pins are not wasted and same program can be used irrespective of ports. So do this at the beginning of the program for better understanding of the program and portability. Practice this when you do programming. Rest program remain same as that I had given my previous book for parallel port.