raspberry pi GPIO control C language

1. initialize

 

write(fd, pinnumber, pinnumber sring length);

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

//////////////////////////////////////////////////

fd = open("/sys/class/gpio/export", O_WRONLY);
if (fd == -1) {
    fprintf (stdout, "Unable to open /sys/class/gpio/export");
}

if (write(fd, QString::number(DEF_OUT_1).toLocal8Bit().data(), QString::number(DEF_OUT_1).length()) != QString::number(DEF_OUT_1).length()) {
    strTemp = "Error writing " + QString::number(DEF_OUT_1);
    fprintf (stdout, strTemp.toLocal8Bit().data());
}
 close(fd);

 

2. direction

strTemp = "/sys/class/gpio/gpio" + QString::number(DEF_OUT_1) + "/direction";
fd = open(strTemp.toLocal8Bit().data(), O_WRONLY);
if (fd == -1) {
    strTemp = "Unable to open " + strTemp;
    fprintf (stdout, strTemp.toLocal8Bit().data());
}
if (write(fd, "out", 3) != 3) {
    strTemp = "Error writing direction " + QString::number(DEF_OUT_1);
    fprintf (stdout, strTemp.toLocal8Bit().data());
}
close(fd);

3. gpio out

strTemp = "/sys/class/gpio/gpio" + QString::number(DEF_OUT_1) + "/value";
fd = open(strTemp.toLocal8Bit().data(), O_RDONLY);
if (fd == -1) {
    strTemp = "Unable to open " + strTemp;
    fprintf (stdout, strTemp.toLocal8Bit().data());
}
else {
    if (write(fd, "0", 1) != 1) {
        strTemp = "Error writing " + strTemp;
        fprintf (stdout, strTemp.toLocal8Bit().data());
    }
}
::close(fd);

4.gpio read

strTemp = "/sys/class/gpio/gpio" + QString::number(DEF_IN_1) + "/value";
fd = open(strTemp.toLocal8Bit().data(), O_RDONLY);
if (fd == -1) {
    strTemp = "Unable to open " + strTemp;
    fprintf (stdout, strTemp.toLocal8Bit().data());
}
else {
    read(fd, &szIO_read, 1);
    szInput_val[0] = szIO_read&0x01;
}
::close(fd);