# Building and flashing PX4

## Prerequisites

You need a build environment that can build PX4 Autopilot. You can generally use the [same environment as with Apache NuttX](https://nxp.gitbook.io/ucans32k1/apache-nuttx/building-and-flashing-nuttx#toolchain), but you will need to install some additional packages. To get started, you can use the [HoverGames virtual machine](https://nxp.gitbook.io/hovergames/developerguide/tools), or install your own Linux (virtual) machine. When you have a basic Linux environment, you only need to [install the PX4 toolchain](https://nxp.gitbook.io/hovergames/developerguide/tools/toolchain-installation) to continue. 

More information is also available in the [PX4 Developer Guide](https://dev.px4.io/master/en/setup/getting_started.html).

If you have not yet cloned the PX4 source code as part of the toolchain installation, you should do so now:

```bash
git clone https://github.com/PX4/PX4-Autopilot
```

## Adding CAN utilities to PX4

If you want to add the `can-utils` apps to PX4 (`candump` and `cansend` applications), you will need to perform an extra step. 

Here are the steps:

1. From the root of your PX4 directory, run `make nxp_ucans32k146 menuconfig`
2. Navigate to `Application Configuration --->`
3. Navigate to `CAN Utilities --->`
4. Enable all options except `[ ] SocketCAN slcan tool`

It should look like this:

![](https://2042189127-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-M7FJ_hQKd8L0MNgduui%2Fuploads%2F0htshprxgmSA6QuxIpsh%2Fimage.png?alt=media\&token=723a9e0b-ae87-44c9-8519-ff67fe868e5f)

Once you've finished this, exit the menuconfig and save, then continue to build PX4 below.

## Building PX4 Autopilot for UCANS32K146

Change  your working directory (`cd` command) to the PX4-Autopilot Git repository that you just cloned. Next we will build the bootloader and firmware for our UCAN board.

### Bootloader

{% hint style="info" %}
You only need to build and flash the bootloader once. If you rebuild/reflash PX4, you can skip all of the bootloader steps.
{% endhint %}

#### Downloading the Bootloader

If you don't want to build the bootloader, you can download it by clicking the file below.

{% embed url="<http://ci.px4.io/job/PX4_misc/job/Firmware-compile/job/master/lastSuccessfulBuild/artifact/build/nxp_ucans32k146_default/nxp_ucans32k146.bin>" %}
UCANS32K146 PX4 Bootloader (Latest build)
{% endembed %}

Alternatively, run the following command to build the bootloader:

```bash
make nxp_ucans32k146_canbootloader
```

The binary file will be located at `PX4-Autopilot/build/nxp_ucans32k146_canbootloader/nxp_ucans32k146.bin`. Keep this file handy for flashing later.

### PX4 Firmware

A prebuilt version of PX4 for UCANS32K146 is linked below. This is the latest build of PX4 master.

{% embed url="<http://ci.px4.io/job/PX4_misc/job/Firmware-compile/job/master/lastSuccessfulBuild/artifact/build/nxp_ucans32k146_default/34-0.1.*.uavcan.bin/*zip*/nxp_ucans32k146_default.zip>" %}
UAVCAN PX4 firmware binary (Latest build)
{% endembed %}

Alternatively, you can build the firmware by running the following command in the root of the PX4-Autopilot repository:

```bash
make nxp_ucans32k146
```

The .bin file for flashing the firmware will be stored in `build/nxp_ucans32k146_default/deploy`. The file you're looking for is `34.bin`. You can leave the file there or copy it to another location for flashing the board in the next section.

## Flashing PX4 Autopilot to the UCANS32K146 board

Download and install the [J-Link Software and Documentation Pack](https://www.segger.com/downloads/jlink#J-LinkSoftwareAndDocumentationPack). It is available for all major operating systems, but we will assume here that you are using a Linux-based OS. Open a terminal and navigate to the directory which holds the `nxp_ucans32k146.bin` file that we build in the previous step.

Now start the J-Link tools by entering:

```bash
JLinkExe
```

Make sure that the debugger is plugged into both the UCANS32K146 board and your computer. If you are using a virtual machine, the debugger USB device should be made available inside the VM. Also do not forget to power the board. Now enter:

```bash
connect
```

You are now asked to specify a device. It is quickest to manually enter the device:

```bash
s32k146
```

The target interface needs to be specified, which is SWD:

```bash
s
```

Finally you have to specify the target interface speed. It is recommended to use 1000 kHz:

```bash
1000
```

Now flash the bootloader with:

```bash
loadbin /path/to/nxp_ucans32k146.bin 0x0
```

The binary will be programmed and this process will also be verified. It should then mention if everything went OK.&#x20;

Next, flash the PX4 firmware binary with:

```bash
# If using pre-built binary
loadbin /path/to/34-0.1.{commit}.uavcan.bin 0x6000
# If using self-built binary
loadbin /path/to/34.bin 0x6000
```

And you're good to go.

You can quit the J-Link tools with:

```bash
q
```

You may need to power cycle the device afterwards. The debug console should now be available on LPUART1 (115200 baud) - which is also accessible on the debugger breakout board.

## More information

The PX4-build for UCANS32K146 is in an early state and not all features may be available. More information about PX4 Autopilot is available in their [User Guide](http://docs.px4.io/master/en/) and [Developer Guide](https://dev.px4.io/master/en/). Their software development is managed on [GitHub](https://github.com/PX4/PX4-Autopilot). There are also various [support channels](https://dev.px4.io/master/en/contribute/support.html) available.