updating Readme

Readme.md

@@ -1,10 +1,182 @@
-# Introduction
-How to compile
+# GPIO Command-Line Tool in C
+
+A simple command-line tool written in C to control Raspberry Pi GPIO pins using the Linux GPIO `sysfs` interface.
+
+The program supports configuring a GPIO as an **input** or **output**, writing a digital value, and reading the state of an input.
+
+## Compile
+
+Compile the program using GCC:
+
+```bash
+gcc main.c -o gpio
+```
+
+## Usage
+
+The general command syntax is:
+
+```bash
+./gpio <gpio> <direction> [value]
+```
+
+### GPIO as Output
+
+Configure GPIO 17 as an output and set it HIGH:
+
+```bash
+./gpio 17 out 1
+```
+
+Set GPIO 17 LOW:
+
+```bash
+./gpio 17 out 0
+```
+
+When `out` is selected, the value argument is required:
+
+```text
+./gpio <gpio> out <0|1>
+```
+
+For example, the following command is invalid:
+
+```bash
+./gpio 17 out
+```
+
+because the output value is missing.
+
+### GPIO as Input
+
+Configure GPIO 17 as an input and read its current digital state:
 
 ```bash
-gcc main.c -o hello
+./gpio 17 in
+```
+
+The program reads the GPIO `value` file and displays either:
+
+```text
+0
+```
+
+or:
+
+```text
+1
 ```
 
-# Issues
+No additional value argument is required for an input.
+
+## Program Flow
+
+The program follows this sequence:
+
+```text
+Command-line arguments
+        │
+        ▼
+Validate direction
+        │
+        ├── out → verify value argument
+        │
+        └── in  → no value required
+        │
+        ▼
+Export GPIO
+        │
+        ▼
+Set GPIO direction
+        │
+        ├── out → gpio_write()
+        │
+        └── in  → gpio_read()
+        │
+        ▼
+Unexport GPIO
+```
+
+## Functions
+
+The program is divided into the following functions:
+
+```c
+int gpio_export(const char *gpio);
+int gpio_direction(const char *gpio, const char *direction);
+int gpio_write(const char *gpio, const char *value);
+int gpio_read(const char *gpio);
+int gpio_unexport(const char *gpio);
+```
+
+Their responsibilities are:
+
+- `gpio_export()` — exports the selected GPIO.
+- `gpio_direction()` — configures the GPIO as `in` or `out`.
+- `gpio_write()` — writes `0` or `1` to an output.
+- `gpio_read()` — reads the digital state of an input.
+- `gpio_unexport()` — releases the GPIO after the operation.
+
+## GPIO sysfs Files
+
+For GPIO 17, the program accesses files such as:
+
+```text
+/sys/class/gpio/chip0/gpio17/direction
+/sys/class/gpio/chip0/gpio17/value
+```
+
+The `direction` file determines whether the GPIO is configured as an input or output.
+
+The `value` file is used to read or write the digital state of the GPIO.
+
+## Example
+
+Output:
+
+```bash
+./gpio 17 out 1
+```
+
+Input:
+
+```bash
+./gpio 17 in
+```
+
+Invalid output command:
+
+```bash
+./gpio 17 out
+```
+
+Expected error:
+
+```text
+Error: GPIO out option requires a value.
+Usage: ./gpio <gpio> out <0|1>
+```
+
+## Current Features
+
+- GPIO export and unexport
+- Input/output direction configuration
+- Digital output (`0` or `1`)
+- Digital input reading
+- Command-line argument validation
+- Invalid direction detection
+
+## Future Work
+
+A future version will include a `blink` operation:
+
+```bash
+./gpio 17 blink 500
+```
+
+where `500` represents the blinking interval in milliseconds.
+
+This version now reflects the structure of your current C implementation, including the separation between argument validation and GPIO operations.
+
 
-- [ ] Error catcher