I am doing a project on Bluetooth based notice board. In this project, a user sends a message using a voice-to-text app. The message is then received by the Bluetooth module and sends it to the 8051 which decodes it and sends it to the LCD for display.
The LCD I am using is 20x4, so it can display at maximum 80 characters, but if it exceeds 80 characters the fourth line will start scrolling the message.
Currently, the code I had provided can receive 9 characters. How to modify this code for receiving different length strings (as the input message the user provides each time will be of different length)? The code is as follows:
#include <reg51.h> #include <string.h> #define LCD_Data_Bus P1 #define FirstLine 0x80 #define SecondLine 0xC0 #define ThirdLine 0x94 #define FourthLine 0xD4 #define MaxSupportedChars 20 #define MaxSupportedLines 4 #define BlankSpace ' ' unsigned int LcdTrackLineNum; // Variable to track the line numbers unsigned int LcdTrackCursorPos; // Variable to track the cursor unsigned int LcdLineNumAddress[]={0x80, 0xc0, 0x94, 0xd4}; sbit _RS= P2^2; // Register select pin connected to P2.2 sbit _RW= P2^1; // Read/Write pin connected to P2.1 sbit _EN= P2^0; // Enable pin connected to P2.0 /* Function prototypes for UART */ void uart_init(); unsigned rx_data(); void delay_ms(unsigned int); /* Function prototypes for LCD */ void lcd_cmd(unsigned char cmd); void lcd_data(unsigned char ascii); void lcd_init(); void lcd_clear(); void LCD_DisplayChar(char LcdData); void lcd_msg(char *); void LCD_GoToNextLine(void); void main() { unsigned char read[10]; unsigned char i; lcd_init(); lcd_clear(); uart_init(); delay_ms(50); lcd_msg("\n Bluetooth based \n Notice Board "); delay_ms(2000); while(1) { lcd_clear(); lcd_cmd(0x80); for (i=0; i<10; i++) { read[i]=rx_data(); LCD_DisplayChar(read[i]); } } } void uart_init() // INITIALIZE SERIAL PORT { TMOD = 0x20; // Timer 1 IN MODE 2-AUTO RELOAD TO GENERATE BAUD RATE TH1 = 0xFD; // LOAD BAUDRATE TO TIMER REGISTER SCON = 0x50; // SERIAL MODE 1, 8-DATA BIT 1-START BIT, 1-STOP BIT, REN ENABLED TR1 = 1; // START TIMER } unsigned rx_data() { while (RI == 0); // WAIT UNTIL DATA IS RECEIVED RI = 0; // CLEAR FLAG return SBUF; // RETURN SERIAL DATA } void delay_ms(unsigned int time) { int i, j; for(i=0; i<=time; i++) for(j=0; j<=127; j++); } void lcd_cmd(unsigned char cmd) { _RS=0; // RS = 0 for Command. _RW=0; // RW = 0 for write. LCD_Data_Bus=cmd; // 8bit command to LCD. _EN=1; // Send a High-to-Low Pusle at Enable Pin. delay_ms(5); _EN=0; delay_ms(5); } void lcd_data(unsigned char ascii) { _RS=1; // RS = 1 for Data. _RW=0; // RW = 0 for write. LCD_Data_Bus=ascii; // 8bit command to LCD. _EN=1; // Send a High-to-Low Pusle at Enable Pin. delay_ms(2); _EN=0; delay_ms(2); } void lcd_init() { delay_ms(5); lcd_cmd(0x38); // Initilize the LCD in 8bit Mode lcd_cmd(0x0E); // Display ON cursor ON lcd_cmd(0x01); // Clear the LCD lcd_cmd(0x80); // Move the Cursor to First line First Position } void lcd_clear() { lcd_cmd(0x01); } void lcd_msg(char *ptr_str) { unsigned char i, j; int Size = strlen(ptr_str); if (Size > 80) { for (i=0; i<Size; i++) LCD_DisplayChar(ptr_str[i]); while(1) { lcd_cmd(0x0C); for (i=60;ptr_str[i]; i++) { lcd_cmd(FourthLine); for (j=0; j<MaxSupportedChars && ptr_str[i+j]; j++) lcd_data(ptr_str[i+j]); for (j=j; j<MaxSupportedChars; j++) lcd_data(BlankSpace); delay_ms(125); } lcd_cmd(0x0E); } } else { while ((*ptr_str) != 0) LCD_DisplayChar(*ptr_str++); } } void LCD_GoToNextLine(void) { LcdTrackLineNum++; LcdTrackCursorPos = 0x00; switch(LcdTrackLineNum) { case 1: lcd_cmd(SecondLine); break; case 2: lcd_cmd(ThirdLine); break; case 3: lcd_cmd(FourthLine); break; } } void LCD_DisplayChar(char LcdData) { if ((LcdTrackCursorPos >= MaxSupportedChars-1 ) || (LcdData=='\n')) { /* If the cursor has reached to end of line on page1 OR NewLine command is issued Then Move the cursor to next line */ LCD_GoToNextLine(); } if (LcdData != '\n') /* Display the character if its not newLine Char */ { lcd_data(LcdData); /* Display the data and keep track of cursor */ LcdTrackCursorPos++; } } 
