update logger README to include detailed usage instructions and examples

Signed-off-by: YoungSoo Shin <shinys000114@gmail.com>

example/logger/README.md

@@ -1,46 +1,140 @@
-# Power Consumption Logger Example
+# Odroid PowerMate Logger and Plotter
 
-Based on this script, you can monitor power consumption and implement graph plotting.
+This directory contains two Python scripts to log power data from an Odroid Smart Power device and visualize it.
 
-## How to Run the Script
+1.  `logger.py`: Connects to the device's web server, authenticates, and logs real-time power data from its WebSocket to a CSV file.
+2.  `csv_2_plot.py`: Reads the generated CSV file and creates a plot image of the power, voltage, and current data over time.
 
-### Install Python Virtual Environment
+## Prerequisites
 
-```shell
+### 1. Clone this example
+```bash
 git clone https://github.com/hardkernel/odroid-powermate.git
 cd odroid-powermate/example/logger
 ```
 
-```shell
-sudo apt install virtualenv
-virtualenv venv
-source venv/bin/activate
+### 2. Python and Virtual Environment
+
+It is highly recommended to use a Python virtual environment to manage project dependencies and avoid conflicts with other projects.
+
+Ensure you have Python 3 installed.
+
+1.  **Create a virtual environment:**
+    Open your terminal in this directory and run:
+    ```bash
+    python3 -m venv venv
+    ```
+    This will create a `venv` directory containing the Python interpreter and libraries.
+
+2.  **Activate the virtual environment:**
+    *   **On Windows:**
+        ```powershell
+        .\venv\Scripts\activate
+        ```
+    *   **On macOS and Linux:**
+        ```bash
+        source venv/bin/activate
+        ```
+    Your terminal prompt should now show `(venv)` at the beginning, indicating that the virtual environment is active.
+
+### 3. Install Required Libraries
+
+With the virtual environment activated, install the necessary Python packages:
+
+```bash
+pip33 install requests websockets protobuf pandas matplotlib python-dateutil
 ```
 
-### Install require package
+### 4. Protobuf Generated File
 
-```shell
-pip install grpcio-tools requests websockets protobuf pandas matplotlib
+The `logger.py` script uses Google Protocol Buffers (Protobuf) to decode real-time data from the WebSocket. This requires a Python file, `status_pb2.py`, which is generated from a Protobuf definition file (`status.proto`).
+
+**How to Generate `status_pb2.py`:**
+
+1.  **Install Protobuf Compiler Tools:**
+    You need the `grpcio-tools` package, which includes the `protoc` compiler and Python plugins. You can install it via pip:
+    ```bash
+    pip3 install grpcio-tools
+    ```
+
+2.  **Locate the `.proto` file:**
+    Ensure you have the `status.proto` file in the current directory. This file defines the structure of the data messages.
+
+3.  **Run the Compiler:**
+    Execute the following command in your terminal. This command tells `protoc` to look for `status.proto` in the directory (`-I../../proto`) and generate the Python output file (`--python_out=.`) in the same place.
+    ```bash
+    python3 -m grpc_tools.protoc -I../../proto --python_out=. status.proto
+    ```
+After running this command, the `status_pb2.py` file will be created, and `logger.py` will be able to use it.
+
+## Usage
+
+The process is a two-step workflow: first log the data, then plot it.
+
+### Step 1: Log Power Data with `logger.py`
+
+Run `logger.py` to connect to your Odroid Smart Power device and save the data to a CSV file.
+
+**Syntax:**
+```bash
+python3 logger.py <host> -u <username> -p <password> -o <output_file.csv>
 ```
 
-### Build `status_pb2.py`
+**Arguments:**
+*   `host`: The IP address or hostname of the Odroid Smart Power device (e.g., `192.168.1.50`).
+*   `-u`, `--username`: The username for logging in.
+*   `-p`, `--password`: The password for logging in.
+*   `-o`, `--output`: The path to save the output CSV file. This is required if you want to generate a plot.
 
-```shell
-python -m grpc_tools.protoc -I ../../proto --python_out=. status.proto
+**Example:**
+
+This command will log in and save the power data to `power_log.csv`.
+
+```bash
+python3 logger.py 192.168.1.50 -u admin -p mypassword -o power_log.csv
 ```
 
-### Execute script
+The script will continue to log data until you stop it with `Ctrl+C`.
 
-#### Power consumption collection
-```shell
-# python3 logger.py -u <username> -o <name.csv> -p <password> <address>
-python3 logger.py -u admin -p password -o test.csv 192.168.30.5 
+### Step 2: Generate a Plot with `csv_2_plot.py`
+
+Once you have a CSV log file, you can use `csv_2_plot.py` to create a visual graph.
+You can also use the csv file recorded from PowerMate Web.
+
+**Syntax:**
+```bash
+python3 csv_2_plot.py <input.csv> <output.png> [options]
 ```
 
-#### Plot data
+**Arguments:**
+*   `input_csv`: The path to the CSV file generated by `logger.py`.
+*   `output_image`: The path to save the output plot image (e.g., `plot.png`).
 
-```shell
-python3 csv_2_plot.py test.csv plot.png [--type power voltage current] [--source vin main usb]
+**Optional Arguments:**
+*   `-t`, `--type`: Specify which plots to generate. Choices are `power`, `voltage`, `current`. Default is all three.
+*   `-s`, `--source`: Specify which power sources to include. Choices are `vin`, `main`, `usb`. Default is all three.
+
+**Example 1: Default Plot**
+
+This command reads `power_log.csv` and generates a plot containing power, voltage, and current for all sources, saving it as `power_graph.png`.
+
+```bash
+python3 csv_2_plot.py power_log.csv power_graph.png
 ```
 
-![plot.png](plot.png)
+**Example 2: Custom Plot**
+
+This command generates a plot showing only the **power** and **current** for the **MAIN** and **USB** sources.
+
+```bash
+# main, usb power consumption
+python csv_2_plot.py power_log.csv custom_plot.png --type power --source main usb
+```
+
+## Example Output
+
+Running the plot script will generate an image file similar to this:
+
+![plot.png](img/plot.png)
+
+The 5-unit scale is highlighted with a blue dotted line, and the 10-unit scale is highlighted with a red dotted line.