# 4. Jetson Nano Development Tutorial

<img class="common_img" src="../_static/media/section_4/media/image3.png" style="width:500px" />

## 4.1 Getting Started

### 4.1.1 Wiring Instruction

This section uses DuPont wires to connect glowy ultrasonic sensor. For wiring instructions, refer to the figure below:

<img class="common_img" src="../_static/media/section_4/media/image4.png" style="width:500px" />

> [!NOTE]
>
> **Before powering on, ensure that no metal objects are touching the controller. Otherwise, the exposed pins at the bottom of the board may cause a short circuit and damage the controller.**

### 4.1.2 Environment Configuration

Install NoMachine on your computer. The software package is located under "**[2 Software Tools & Programs -\> 01 Software Installation Package -\> Remote Desktop Connection Tool](https://drive.google.com/drive/folders/1E7j2At6guFY7DP1m_pJMMDWaqk78y1Uq?usp=sharing)"**. For the detailed operations of NoMachine, please refer to the relevant tutorials.

**Drag the program into the Jetson Nano system image, taking placing it on the desktop as an example.**

Open the terminal and enter the command to navigate to the program directory, enter:

```bash
cd Desktop/
```

## 4.2 Test Case

This case demonstrates that the glowy ultrasonic module detects distance and changes color accordingly.

### 4.2.1 Program Execution

Run the program by entering:

```bash
python3 ultrasonic_sonar.py
```

### 4.2.2 Project Outcome

The glowy ultrasonic module will print the detected target distance on the terminal, while the RGB lights on the module will change color gradually.

### 4.2.3 Program Brief Analysis

- **Import Libraries**

```py
from sonar import Sonar 
import time
```

`Sonar`: An initialized object used to configure the light mode and color.

`time`: A library related to time functions, used for setting timers and calculating time intervals.

- **Instantiation Class**

```py
def main():
    S = Sonar()
    # Set RGB mode: 0 = user direct color control, 1 = breathing cycle (超声波的灯光有两种模式，模式0 用户直接控制灯光发出某种颜色, 模式1控制灯光周期变化)
    S.set_rgb_mode(0)  # Set to mode 0 (设置为模式0)
    # Set color for left/right LEDs: 0 = left, 1 = right (超声波的两个"眼睛" 对应两个灯用0, 1 表示)
    S.set_color(0, 0xFF0000)  # Set light 0 to red, 0xFF0000 is the RGB value of the light to be emitted (0 号灯设为 红色 0xFF0000 是要发出的灯光的RGB值)
    S.set_color(1, 0x00FF00) # Set light 1 to green (1号灯设为 绿色 )
    time.sleep(2)

    S.set_rgb_mode(1)  # Set to mode 1 (设置为 模式1)
    
    # Configure breathing cycles for LED 0 
    S.set_breath_cycle(0, 0, 0) # Red channel off  (将0号灯的红色设置的呼吸亮灭周期设为0, 就是完全熄灭)
    S.set_breath_cycle(0, 1, 0)  # Green channel off (将0号灯的绿色设置的呼吸亮灭周期设为0, 就是完全熄灭)
    S.set_breath_cycle(0, 2, 1000) # Blue channel 1000ms cycle (将0号灯的色蓝色设置的呼吸亮灭周期设为1000毫秒)
 
    time.sleep(2)
    
    # Configure breathing cycles for LED 1 
    S.set_breath_cycle(1, 0, 500) # Red channel 500ms cycle(将1号灯的红色设置的呼吸亮灭周期设为500毫秒)
    S.set_breath_cycle(1, 1, 0) #Green channel off(将1号灯的绿色设置的呼吸亮灭周期设为0,  就是完全熄灭)
    S.set_breath_cycle(1, 2, 1000) #Blue channel 1000ms cycle (将1号灯的色蓝色设置的呼吸亮灭周期设为1000毫秒)

    time.sleep(2)


    #Start RGB light symphony(此外可以使用start_symphony来让rgb灯自行幻彩变化)
    S.start_symphony()
```

Instantiate the glowy ultrasonic class, and define its related attributes, such as detected distance, RGB color and breathing light mode.

- **Get Detection Distance**

```py
distance = None
    last_print_time = time.time()
    while True:
        d = S.get_distance()  # Read distance in mm (读取超声波的距离，单位mm)

        # # Simple filtering to reduce sudden jumps (我们可以做点简单的滤波应对可能出现的跳变和错误数据)
        if distance is None:
            distance = d
        else:
            distance = distance * 0.6 + d * 0.4 ## Weight: 0.4 new, 0.6 previous(这次测量的距离权重0.4, 之前数值权重0.6)
```

Call `get_distance` to read the ultrasonic module's I2C pins, obtain the current distance to the obstacle, and return the value.

- **Print Detection Distance Data**

```py
 # Print distance once per second (每秒打印一次数据)
        if last_print_time < time.time():
            last_print_time = time.time() + 1
            print(distance)

        #Read ultrasonic data every 0.1s (每0.1秒读取一次超声波数据)
        time.sleep(0.1)
```

In the loop, the terminal continuously prints the obstacle distance detected by the ultrasonic module.