8051-Keypad-Interfacing-Code.rar_8051 keypad

// *********************************************************** // Project: Keypad Interfacing with 8051 // Author: M.Saeed Yasin // Module description: Get input from keypad and display it on LCD // *********************************************************** #include<reg51.h> //Function declarations void cct_init(void); void delay(int); void lcdinit(void); void writecmd(int); void writedata(char); void Return(void); char READ_SWITCHES(void); char get_key(void); //******************* //Pin description /* P2 is data bus P3.7 is RS P3.6 is E P1.0 to P1.3 are keypad row outputs P1.4 to P1.7 are keypad column inputs */ //******************** // Define Pins //******************** sbit RowA = P1^0; //RowA sbit RowB = P1^1; //RowB sbit RowC = P1^2; //RowC sbit RowD = P1^3; //RowD sbit C1 = P1^4; //Column1 sbit C2 = P1^5; //Column2 sbit C3 = P1^6; //Column3 sbit C4 = P1^7; //Column4 sbit E = P3^6; //E pin for LCD sbit RS = P3^7; //RS pin for LCD // *********************************************************** // Main program // int main(void) { char key; // key char for keeping record of pressed key cct_init(); // Make input and output pins as required lcdinit(); // Initilize LCD while(1) { key = get_key(); // Get pressed key writecmd(0x01); // Clear screen writedata(key); // Echo the key pressed to LCD } } void cct_init(void) { P0 = 0x00; //not used P1 = 0xf0; //used for generating outputs and taking inputs from Keypad P2 = 0x00; //used as data port for LCD P3 = 0x00; //used for RS and E } void delay(int a) { int i; for(i=0;i<a;i++); //null statement } void writedata(char t) { RS = 1; // This is data P2 = t; //Data transfer E = 1; // => E = 1 delay(150); E = 0; // => E = 0 delay(150); } void writecmd(int z) { RS = 0; // This is command P2 = z; //Data transfer E = 1; // => E = 1 delay(150); E = 0; // => E = 0 delay(150); } void lcdinit(void) { ///////////// Reset process from datasheet ///////// delay(15000); writecmd(0x30); delay(4500); writecmd(0x30); delay(300); writecmd(0x30); delay(650); ///////////////////////////////////////////////////// writecmd(0x38); //function set writecmd(0x0c); //display on,cursor off,blink off writecmd(0x01); //clear display writecmd(0x06); //entry mode, set increment } void Return(void) //Return to 0 location on LCD { writecmd(0x02); delay(1500); } char READ_SWITCHES(void) { RowA = 0; RowB = 1; RowC = 1; RowD = 1; //Test Row A if (C1 == 0) { delay(10000); while (C1==0); return '7'; } if (C2 == 0) { delay(10000); while (C2==0); return '8'; } if (C3 == 0) { delay(10000); while (C3==0); return '9'; } if (C4 == 0) { delay(10000); while (C4==0); return '/'; } RowA = 1; RowB = 0; RowC = 1; RowD = 1; //Test Row B if (C1 == 0) { delay(10000); while (C1==0); return '4'; } if (C2 == 0) { delay(10000); while (C2==0); return '5'; } if (C3 == 0) { delay(10000); while (C3==0); return '6'; } if (C4 == 0) { delay(10000); while (C4==0); return 'x'; } RowA = 1; RowB = 1; RowC = 0; RowD = 1; //Test Row C if (C1 == 0) { delay(10000); while (C1==0); return '1'; } if (C2 == 0) { delay(10000); while (C2==0); return '2'; } if (C3 == 0) { delay(10000); while (C3==0); return '3'; } if (C4 == 0) { delay(10000); while (C4==0); return '-'; } RowA = 1; RowB = 1; RowC = 1; RowD = 0; //Test Row D if (C1 == 0) { delay(10000); while (C1==0); return 'C'; } if (C2 == 0) { delay(10000); while (C2==0); return '0'; } if (C3 == 0) { delay(10000); while (C3==0); return '='; } if (C4 == 0) { delay(10000); while (C4==0); return '+'; } return 'n'; // Means no key has been pressed } char get_key(void) //get key from user { char key = 'n'; //assume no key pressed while(key=='n') //wait untill a key is pressed key = READ_SWITCHES(); //scan the keys again and again return key; //when key pressed then return its value }