# Line Tracing

ine Tracing is usually used in line tracing robots, we will learn how to obtain the coordinates of the line (x1,y1) & (x2,y2 )in this tutorial.

### Getting coordinates

<figure><img src="https://kittenbothk-eng.readthedocs.io/en/latest/_images/mcbanner.png" alt=""><figcaption></figcaption></figure>

#### **Loading Extensions**

Search "KOI" in the search bar.

<figure><img src="https://kittenbothk.readthedocs.io/en/latest/_images/koi_search.png" alt=""><figcaption></figcaption></figure>

Or copy and paste the following link to the search bar.

**<https://github.com/KittenBot/pxt-koi>**

Blocks for Line Tracing:

<figure><img src="https://kittenbothk-eng.readthedocs.io/en/latest/_images/image4154.png" alt=""><figcaption></figcaption></figure>

#### Sample Program

{% embed url="<https://makecode.microbit.org/_T9747v0Vdd2q>" %}

### Color Calibration

Line Tracing and Blob Tracing both require calibration before using.

<figure><img src="https://kittenbothk-eng.readthedocs.io/en/latest/_images/calibrate.png" alt=""><figcaption></figcaption></figure>

During calibration, a small green square will appear on the screen. Aim the square at the color you intend to track. The calibration will be done automatically.

It is recommended to have a distinct difference between the color you intend to track and the background.

<figure><img src="https://kittenbothk.readthedocs.io/en/latest/_images/042.png" alt=""><figcaption></figcaption></figure>

### Program Flow

Download the program to the Micro:bit.

Put a thin object in front of the camera and press A to calibrate color.

After calibration, the coordinates of the line will be shown on the screen.

### Advanced Program

The information becomes more easily readable if we add an OLED screen.

#### Connecting an OLED

Connect an OLED panel to the I2C port of your Robotbit/Armourbit.

<figure><img src="https://kittenbothk.readthedocs.io/en/latest/_images/03.png" alt=""><figcaption></figcaption></figure>

#### Sample Program

{% embed url="<https://makecode.microbit.org/_MViMLk0uhb70>" %}

The program works the same way as the normal program, but now the coordinates are displayed on the oled.

<figure><img src="https://kittenbothk.readthedocs.io/en/latest/_images/015.png" alt=""><figcaption></figcaption></figure>

### Sample Codes

[1. Line Tracing (Extension0.5.7)](https://makecode.microbit.org/_DriAw4Hi5YDe)

[2. Line Tracing /w OLED (Extension0.5.7)](https://makecode.microbit.org/_KJXToKVxW8do)

### Extension Version and Updates

There may be updates to extensions periodically, please refer to the following link to update/downgrade your extension.

[Makecode Extension Update](https://kittenbothk-eng.readthedocs.io/en/latest/Makecode/makecode_extensionUpdate.html)

### FAQ

#### 1: There is no reaction after pressing the buttons on the Micro:bit.

· A: This is because KOI has a longer boot time than Micro:bit. When the power is turned on, Micro:bit has already ran the code for KOI initialization before KOI is ready.

· Solution: Reset your Micro:bit after KOI has been turned on. (The trick is to let KOI power on completely before initialization.)

#### 2: Does KOI work with 3V input?

· A: No, KOI only works with 5V.

#### 3: How to improve line tracing accuracy?

· A: Keep a clean background and use a color that is significantly different from the background.


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