Add readme

README.md

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+# GPIO_FTDI
+
+Gpio driver using ftdi usb chips e.g.:
+
+```shell
+$ lsusb
+Bus 001 Device 008: ID 0403:6001 Future Technology Devices International, Ltd FT232 Serial (UART) IC
+```
+
+## Requirements
+
+* libftdi1
+* libftdi1-dev
+
+### Debian
+
+```shell
+apt install libftdi1 libftdi1-dev
+```
+
+### Alpine Linux
+
+```shell
+apk add libftdi1 libftdi1-dev
+```
+
+## Installation
+
+```shell
+make install
+```
+
+Installs `lobgpio_ftdi.a` and `libgpio_ftdi.so` in the directory `$(PREFIX)/lib/`. It also installs the include header files `ftdi_dev.h` and `gpio.h` in the directory `$(PREFIX)/include/gpio_ftdi`. 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 install
+```
+
+Removes the files installed with the `install` make target.  
+> **NOTE:** When `PREFIX` variable was changed during installation process the same value needs to be set for uninstallation. E.g.:
+
+```shell
+PREFIX=/usr/local/ make install
+```
+
+## Example
+
+```C
+    #include <stdio.h>
+    #include <stdlib.h>
+    #include <unistd.h>
+    #include <syslog.h>
+    #include <stdbool.h>
+    #include <ftdi_dev.h>
+    #include <gpio.h>
+
+    static struct ftdi_dev ftdi_obj = {
+        .ftdi = NULL,
+        .is_open = false,
+        .vendor_id = 0x0403,
+        .product_id = 0x6001,
+        .bit_mask = 0,
+        .status_mask = 0,
+    };
+
+    static const struct gpio gpio_1 = {
+        .pin = 0x08, /* CTS (brown wire on FTDI cable) */
+        .ftdi_dev = &ftdi_obj,
+    };
+
+    int main(void)
+    {
+        int res, cnt;
+        unsigned int value;
+
+        openlog("ftdi_gpio", LOG_CONS | LOG_PID | LOG_NDELAY, LOG_LOCAL1);
+
+        res = gpio_open(&gpio_1);
+        if(res != EXIT_SUCCESS) {
+            syslog(LOG_ERR, "Unable to open gpio\n");
+            return res;
+        }
+
+        gpio_write(&gpio_1, 1);
+        for(cnt = 0; cnt < 10; cnt++) {
+            gpio_toggle(&gpio_1);
+            gpio_read(&gpio_1, &value);
+            printf("Gpio1: %u\n", value);
+            sleep(1);
+        }
+        gpio_close(&gpio_1);
+
+        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.                                   |
+| 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).                            |