ラズパイとC言語を使った「ライブラリの作成方法」

//LCD表示に必要な関数
extern void write_word(int data);
extern void send_command(int comm);
extern void send_data(int data);
extern void init();
extern void clear();
extern void write(int x, int y, char data[]);

#include <stdio.h>
#include <wiringPi.h>
#include <wiringPiI2C.h>
#include <string.h>
#include "lcdPi.h"

int LCDAddr = 0x27;//I2c address of LCD, some LCD i2c address might be 0x27
int BLEN = 1;//1--open backlight.0--close backlight
int fd;//linux file descriptor

//send an  16 bits data to LCD buffer
void write_word(int data){
    int temp = data;
    if ( BLEN == 1)
        temp |= 0x08;
    else
        temp &= 0xF7;
    wiringPiI2CWrite(fd, temp);
}
//send control command to lcd
void send_command(int comm){
    int buf;
    // Send bit7-4 firstly
    buf = comm & 0xF0;
    buf |= 0x04;            // RS = 0, RW = 0, EN = 1
    write_word(buf);
    delay(2);
    buf &= 0xFB;            // Make EN = 0
    write_word(buf);
    // Send bit3-0 secondly
    buf = (comm & 0x0F)<<4; 
    buf |= 0x04;            // RS = 0, RW = 0, EN = 1
    write_word(buf);
    delay(2);
    buf &= 0xFB;            // Make EN = 0
    write_word(buf);
}
//send character to lcd
void send_data(int data){
    int buf;
    // Send bit7-4 firstly
    buf = data & 0xF0;
    buf |= 0x05;            // RS = 1, RW = 0, EN = 1
    write_word(buf);
    delay(2);
    buf &= 0xFB;            // Make EN = 0
    write_word(buf);
    // Send bit3-0 secondly
    buf = (data & 0x0F) << 4;
    buf |= 0x05;            // RS = 1, RW = 0, EN = 1
    write_word(buf);
    delay(2);
    buf &= 0xFB;            // Make EN = 0
    write_word(buf);
}
//initialize the lcd
void init(){
    fd = wiringPiI2CSetup(LCDAddr);//追加しました
    send_command(0x33); // Must initialize to 8-line mode at first
    delay(5);
    send_command(0x32); // Then initialize to 4-line mode
    delay(5);
    send_command(0x28); // 2 Lines & 5*7 dots
    delay(5);
    send_command(0x0C); // Enable display without cursor
    delay(5);
    send_command(0x01); // Clear Screen
    wiringPiI2CWrite(fd, 0x08);
}
//clear screen
void clear(){
    send_command(0x01); //clear Screen
}
//Print the message on the lcd
void write(int x, int y, char data[]){
    int addr, i;
    int tmp;
    if (x < 0) x = 0; 
    if (x > 15) x = 15;
    if (y < 0) y = 0; 
    if (y > 1)  y = 1;
    // Move cursor
    addr =  0x80 + 0x40 * y + x;
    send_command(addr);
    
    tmp = strlen(data);
    for (i = 0; i < tmp; i++){
        send_data(data[i]);
    }
}

gcc -Wall -o lcdPi lcdPi.c -lwiringPi

cd pi_practice(ソースコードのあるディレクトリへ）

ar rcs liblcdPi.a lcdPi.o

gcc -Wall -o"%e""%f" -lwiringPi -lpthread -g -o0 liblcdPi.a

 ./lcdPi liblcdPi.a

#include <stdio.h>
#include <wiringPi.h>
#include <wiringPiI2C.h>
#include <string.h>
#include "lcdPi.h"

int main(void){
	init();
	while(1){
	write(0,0,"ohayo");
	delay(3000);
	clear();
}
	return 0;
}