> For the complete documentation index, see [llms.txt](https://nxp.gitbook.io/ucans32k1/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://nxp.gitbook.io/ucans32k1/ucans32k1sic-demo-application/demo-apa102-rgb-led-control-via-ucans32k146-with-px4-autopilot.md).

# DEMO: APA102 RGB LED control via UCANS32K146 with PX4-Autopilot

## Introduction

\
This tutorial explains how to operate 3-LED APA102 RGB board via UCANS32K146 over SPI.

## Items Needed

* An APA102 based RGB LED board 
* UCANS32K146 or UCANS32K1SIC
* Jumper wires
* STEMMA QT / Qwiic JST SH 4-pin Cable
* Segger J-Link debugger

## APA102 LED Board

#### Connections

The input connector of 3-LED APA102 board has 4 wired connections: SDI, CKI, PWR, GND. To connect the LED board to the UCAN board, refer the configuration of 'stemma qt / qwiic jst sh cable'. The connections would be as follows:

<table><thead><tr><th width="268">3-LED APA102 Board Input</th><th width="124.33333333333331">Name</th><th>SPI Port (P1) Pin Number on UCAN</th></tr></thead><tbody><tr><td>Red</td><td>PWR (5V)</td><td>1</td></tr><tr><td>Yellow</td><td>CLK</td><td>2</td></tr><tr><td>Blue</td><td>MOSI</td><td>4</td></tr><tr><td>Black</td><td>GND</td><td>7</td></tr></tbody></table>

#### ![](/files/CnqRHUt8djrgaoUssesY)![](/files/oSGfKDekarJGkF4LGXh6)

#### Network

All the LEDs in the board are daisy chained together. Note: These ***boards*** can also be daisy chained from one board to the next. From the software point of view these are just considered one long string of LEDs daisy chained together.

<figure><img src="/files/7ncO9aIBjXEypr1vm5Dn" alt=""><figcaption></figcaption></figure>

## Software Procedure

Note: You may refer the steps for building and flashing PX4 on this gitbook [link](/ucans32k1/px4-autopilot/building-and-flashing-px4.md).

#### Software Setup

```
git clone -b UCANS32K146 https://github.com/NXPHoverGames/PX4-Autopilot.git --recursive
cd PX4-Autopilot
```

Change the value of 'NUM\_LEDS' in '/platforms/nuttx/NuttX/apps/examples/apa102/apa102\_main.c' to the number of LEDs in your APA102 board. For our case, it will be '3'.

#### Building PX4

```
make nxp_ucans32k146_canbootloader
  // output: build/nxp_ucans32k146_canbootloader/nxp_ucans32k146_canbootloader.bin
make nxp_ucans32k146
  // output: build/nxp_ucans32k146_default/deploy/34.bin
```

After compilation is done, the new firmware is available under: *build/nxp\_ucans32k146\_default/deploy/34.bin*

#### Flashing PX4

Flash the firmware and bootloader, if the board already doesn't have one, using 'jlink.exe'.&#x20;

{% hint style="info" %}
You may flash the attached files (configured for a 3-LED APA102 board), to skip the above steps.
{% endhint %}

{% file src="/files/LE5q6RshMnSOfHvLafFN" %}
PX4-Autopilot Bootloader
{% endfile %}

{% file src="/files/kCF8SYQf6bW3E8S3MTJ5" %}
PX4-Autopilot Firmware
{% endfile %}

```
connect
// specify the following:
  // device: s32k146;
  // target interface: s (which stands for swd);
  // interface speed: 1000 khz (recommended);
loadbin <path to nxp_ucans32k146.bin> 0x0
loadbin <path to 34.bin> 0x6000
// quit jlink tools by typing 'q'.
```

### Operating the LEDs

Connect your board and access to the terminal using MobaXterm, minicom,...

Type the following command:&#x20;

```
apa102
```

<figure><img src="/files/3RiLaX2av6dCgrG8A8Rw" alt=""><figcaption></figcaption></figure>