# 2. Arduino Development
## 2.1 Getting Started
### 2.1.1 Wiring Instruction
Follow the diagram below to complete the wiring for this section.
> [!NOTE]
>
> * **When using Hiwonder's lithium battery, connect the battery cable with the red wire to the positive (+) terminal and the black wire to the negative (–) terminal of the DC port.**
>
> * **If the battery is not connected to the cables, do not connect the cable ends directly together. Doing so may cause a short circuit and damage the system.**
>
> * **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.**
### 2.1.2 Environment Configuration
You can install the Arduino IDE on a PC. Download path: **"[Appendix-> Arduino Installation Package](https://drive.google.com/drive/folders/14LTYZuZ7FePCMK85bTmXPaO3jIvLlgGI?usp=sharing)"** For detailed usage of the Arduino IDE, please refer to the documentation in the same directory.
## 2.2 Test Case
Program to detect distance and displays the specific value in the terminal window.
### 2.2.1 Program Download
1) For the Arduino and UNO development board equipped with the expansion board, use a USB cable to connect them to the computer. You can open Arduino IDE, click "**File → New,**" and import the program located in the same directory as this tutorial.
2) Remember to select the correct development board and port. The ports shown below are for reference only. Then compile and upload the program.
3) After the code is uploaded, click 
to open the serial monitor, set the baud rate to 9600 to observe the output.
### 2.2.2 Project Outcome
The serial monitor displays the distance between the ultrasonic sensor and the obstacle in front, in centimeters.
### 2.2.3 Program Brief Analysis
- **Initialization**
```c++
int inputPin=4; // define ultrasonic signal receiver pin ECHO to D4
int outputPin=5; // define ultrasonic signal transmitter pin TRIG to D5
void setup()
{
Serial.begin(9600);
pinMode(inputPin, INPUT);
pinMode(outputPin, OUTPUT);
}
```
First, Initialize the interfaces: connect the ultrasonic sensor's ECHO and TRIG pins to D4 and D5, respectively.
Then, initialize the serial port and set D4 as input and D5 as output.
- **Loop Process**
```c++
void loop()
{
digitalWrite(outputPin, LOW);
delayMicroseconds(2);
digitalWrite(outputPin, HIGH); // Ultrasonic detection is activated by a 10 μs pulse
delayMicroseconds(10);
digitalWrite(outputPin, LOW);
int distance = pulseIn(inputPin, HIGH); // Read the pulse duration from the receiver
distance= distance/58; // Convert the pulse duration into distance
Serial.print("Distance:");
Serial.print(distance); //Output the data
Serial.println("cm");
delay(50);
}
```
Trigger the ultrasonic sensor to perform detection. The measured data is then processed and output to the terminal window.