gpio_sys/README.md

# GPIO_SYS

Gpio driver using sys file systeme.g.:

```shell
echo "4" > /sys/class/gpio/export
echo "out" > /sys/class/gpio/gpio4/direction
echo "1"> /sys/class/gpio/gpio4/value
echo "4" > /sys/class/gpio/unexport
```

## Installation

```shell
make install
```

Installs `libgpio_sys.a` and `libgpio_sys.so` in the directory `$(PREFIX)/lib/`. It also installs the include header file `gpio.h` in the directory `$(PREFIX)/include/gpio_sys/`. The default value for `PREFIX` is: `PREFIX=usr`. To use another location for installation changing the value of the `PREFIX` variable is needed. E.g.:

```shell
PREFIX=/usr/local/ make install
```

## Uninstallation

```shell
make uninstall
```

Removes the files installed with the `install` make target.  
> **NOTE:** If `PREFIX` variable was changed during installation process the same value needs to be set for uninstallation. E.g.:

```shell
PREFIX=/usr/local/ make uninstall
```

## Example

```C
    #include <stdio.h>
    #include <stdlib.h>
    #include <unistd.h>
    #include <syslog.h>
    #include <stdbool.h>
    #include <gpio_sys/gpio.h>


    static const struct gpio_sys gpio_4 = {
        .pin = 4,
        .direction = 0, // out
    };

    int main(void)
    {
        int res, cnt;
        int value;

        openlog("gpio_sys", LOG_CONS | LOG_PID | LOG_NDELAY, LOG_LOCAL1);

        res = gpio_open(&gpio_4);
        if(res != EXIT_SUCCESS) {
            syslog(LOG_ERR, "Unable to open gpio %d\n", gpio_4.pin);
            return res;
        }

        gpio_write(&gpio_4, 1);
        for(cnt = 0; cnt < 10; cnt++) {
            if(cnt % 2) {
                gpio_write(&gpio_4, 1);
            } else {
                gpio_write(&gpio_4, 0);
            }
            value = gpio_read(&gpio_4);
            if(value < 0) {
                syslog(LOG_ERR, "Unable to read from gpio %d\n", gpio_4.pin);
                return EXIT_FAILURE;
            } else {
                printf("Gpio 4: %d\n", value);
            }
            sleep(1);
        }
        gpio_close(&gpio_4);

        return EXIT_SUCCESS;
    }
```

## Additional make targets

| Target          | Meaning                                                     |
| --------------- | ----------------------------------------------------------- |
| all             | Build the code, assemble the static and shared library.     |
| install         | Install the libraries and necessary include header files.   |
| uninstall       | Uninstall the libraries and necessary include header files. |
| clean           | Clean up build artifacts.                                   |
| distclean       | Remove all directories created while any build step.        |
| build_unit_test | Build the unit tests.                                       |
| exec_unit_test  | Execute the unit tests.                                     |
| coverage        | Determine code coverage of the unit tests.                  |
| check           | Static code analysis (cppcheck).                            |