computer interfacing AVR with UART+LCD
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 SERIAL PORT with LCD DISPLAY serial9 //lcd initializations Init_Ports(); Init_Lcd(); InitUART( 25 ); /* Set the baudrate to 2400 bps using a 1MHz crystal */ for(;;) /* Forever */ { a=ReceiveByte(); Lcd_Send(a); TransmitByte(a); /* Echo the received character */ } serial10 First initialising LCD ports and start initialising baud rates. First we receive the data from serial port and send it to LCD first then it is again send back to serial port. But this process will be having some delays because of the delays inserted in the LCD functions. FOLDER: serialport_lcd(see file-avrbook.rar from yahoo group-booksbybibin) /*---------------------------------------------------------------- -----------------HEADER FILES------------------------------------- -----------------------------------------------------------------*/ #include "lcd.c" //including lcd file /*---------------------------------------------------------------- -----------------FUNCTIONS--------------------------------------- -----------------------------------------------------------------*/ void InitUART( unsigned char baudrate ); unsigned char ReceiveByte( void ); void TransmitByte( unsigned char data ); /*---------------------------------------------------------------- -----------------MAIN FUNCTION------------------------------------ -----------------------------------------------------------------*/ void main() { unsigned char a; //lcd initializationsa Init_Ports(); Init_Lcd(); InitUART( 25 ); /* Set the baudrate to 2400 bps using a 1MHz crystal */ for(;;) /* Forever */ { a=ReceiveByte(); Lcd_Send(a); TransmitByte(a); /* Echo the received character */ } } /*---------------------------------------------------------------- ------------FUNCTIONS TO Initialize UART-------------------------- -----------------------------------------------------------------*/ void InitUART( unsigned char baudrate ) { UBRRL = baudrate; /* Set the baud rate */ UCSRB = (UCSRB | _BV(RXEN) | _BV(TXEN) ); /* Enable UART receiver and transmitter */ } /*---------------------------------------------------------------- ------------FUNCTIONS TO READ UART------------------------------- -----------------------------------------------------------------*/ unsigned char ReceiveByte( void ) { while ( !(UCSRA & (_BV(RXC))) ); /* Wait for incomming data */ return UDR;/* Return the data */ } /*---------------------------------------------------------------- ------------FUNCTIONS TO WRITE UART------------------------------- -----------------------------------------------------------------*/ void TransmitByte( unsigned char data ) { while ( !(UCSRA & (_BV(UDRE))) ); /* Wait for empty transmit buffer */ UDR = data; /* Start transmittion */ } lcd.c /*---------------------------------------------------------------- -----------------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); /*---------------------------------------------------------------- -----------------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)) ); }