# Circle Tracing

### Circle Tracing

<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 circle tracing:

<figure><img src="https://kittenbothk-eng.readthedocs.io/en/latest/_images/01-1.png" alt=""><figcaption></figcaption></figure>

### Sample Program

{% embed url="<https://makecode.microbit.org/_P3wiD8Mur89Y>" %}

#### Threshold

![](https://kittenbothk-eng.readthedocs.io/en/latest/_images/04-12.png)

Threshold affects the detection rate, testing and fine tuning the value is needed for achieving the best results.

A higher threshold value decreases interference and noise, but detection difficulty increases at the same time, please trial and fine tune for different scenarios.

### Program Flow

Download the program to Micro:bit, then press A on the Micro:bit.

The radius of the circle is shown on the Micro:bit while its coordinates are shown on the KOI.

### 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/03-1.png" alt=""><figcaption></figcaption></figure>

#### Sample Program

{% embed url="<https://makecode.microbit.org/_5E21sPM6vaqV>" %}

### Sample Code

[1. Circle Tracing (Extension0.5.7)](https://makecode.microbit.org/_h87fXzXxPhWU)

[2. Circle Tracing /w OLED (Extension0.5.7)](https://makecode.microbit.org/_eFkaX2iT57Hr)

### 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 do I improve detection rate?

· Adjust the threshold value.

· Keep a clean background.

· Make sure the circle has a sharp outline.


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