# 4. Jetson Nano Development Tutorial

<img class="common_img" src="../_static/media/chapter_1/section_4/media/image3.png" style="width:300px" />

## 4.1 Getting Started

### 4.1.1 Wiring Instruction

This section uses DuPont wires to connect digital tube module. For wiring instructions, refer to the figure below:

<img class="common_img" src="../_static/media/chapter_1/section_4/media/image4.png" style="width:700px" />

> [!NOTE]
>
> **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 -\> 1 Remote Desktop Connection Tool](https://drive.google.com/drive/folders/1Zo_aqjHFcxcDNgYyJHAIRXoOxozrl22U?usp=sharing)"**. For detailed usage of NoMachine, refer to the materials in the same directory.

**Drag the program into the Jetson Nano system image. As an example, place it on the desktop.**  Ensure that both **"digital_display.py"** and **"tm1640.py"** are stored in the same directory.

## 4.2 Test Case

In this case, the digital tube is controlled by the program to display the specified information.

### 4.2.1 Program Execution

1. Open the terminal and enter the following command to navigate to the program directory:

```bash
cd Desktop/
```

2. Run the program by entering:

```bash
Python3 digital_display.py
```

### 4.2.2 Project Outcome

After executing the program, the digital tube module will display the number **"1234"**.

### 4.2.3 Program Brief Analysis

- **Import Libraries**

```py
from tm1640 import TM1640 
import time
```

Import the library files required by the program, including the library files needed for delay and the library files for using GPIO pins on the Jetson controller.

- **Initialization Operation**

```py
# Character pattern data (字模数据)
font = {'0':0x3f,'1':0x06,'2':0x5b,'3':0x4f,'4':0x66,'5':0x6d,'6':0x7d,'7':0x07,'8':0x7f,'9':0x6f, '-': 0x40}
```

Define the dictionary **"font"**, which contains the segment codes for digits 0–9 and the symbol **"–"** on the digital tube module.

- **Main Function**

```py
def main():
    mtx = TM1640(6, 10) #6, 10 correspond to CLK and DIO pin numbers (6, 10 对应 CLK，DIO 引脚号)
    mtx.gram = (0x06,0x5b,0x4f,0x66)  # gram serves as display memory for the LED matrix, each byte represents one digit (gram用作点阵的显存，共4个字节，一个字节对应一位数字)
    mtx.refresh()
    time.sleep(1)
    
if __name__ == '__main__':
    main()
```

Initialize the pins 6 and 10 of GPIO, and then set the value displayed by the digital tube through the dictionary defined by the signature, that is: 1234;

Then use the `mtx.refresh ()` function to control the digital tube to refresh. The time.sleep sets the duration to 1 second, meaning the digital tube refreshes every 1 second.