Building an embedded Linux system using PetaLinux 2023.2
Most of the steps we executed while using PetaLinux 2024.1 are still applicable when transitioning to PetaLinux 2023.2. The primary difference is that some commands in PetaLinux 2023.2 were deprecated in 2024.1, so we needed to revert to the older versions of those commands.
Creating a PetaLinux project
We again began with the 2023.2 BSP version for the Ultra96v2. The petalinux-createcommand has an extra -tflag to indicate the type of the project:
Modifying our PetaLinux project
After the PetaLinux project is created, we first make some modifications before we start building our project.
Adding our custom XSA
First of all, we want to add our custom XSA-file to the project. We do this with petalinux-config:
Upgrading Bluez5
We upgraded BlueZ5 to version 5.79. The steps required to complete this upgrade are documented here.
Adding libfreeaptx
In our project, we will support HD audio streaming over Bluetooth, which can be achieved using the aptX-HD codec. To enable this support, we need to install an additional library. The libfreeaptx library is an open-source implementation of the aptX-HD codec and is required by the bluez-alsa package to support aptX-HD. The steps we followed to install this library are documented here.
Adding Bluez-Alsa
We will use the bluez-alsa package to route audio from a Bluetooth device to an ALSA sink. The steps to add this package are documented here.
Adding a Wifi network
For convenience, we ensured that the wpa_supplicant.conf file contained a network configuration before the first boot, allowing the Ultra96-V2 to automatically connect to the network. This eliminates the need for a JTAG UART-to-USB header. The steps to configure this are documented here.
Changing the hostname
Furthermore, we changed the system's hostname from u96v2-sbc-base-2023-2 to blendinator to align with our project. The steps to perform this change are documented here.
Adding support for MIDI
In this project, we will work with MIDI inputs. To be able to do this. We need to enable some Device Drivers. We do this by running the following command:
We navigate to Device Drivers → Sound cart support → Advanced Linux Sound Architecture and enable Sequencer support.
Next, we run the following command:
In the grahpical interface, we navigate to Filesystem Packages → console → utils → alsa-utils and enable alsa-utils and alsa-utils-midi.
Adding ALSA plugins for Bluetooth Audio
On top of the already enabled alsa-utils, we will also enable alsa-plugins so that we get access to extra features like the ALSA resampler. We will need this later on to resample Bluetooth audio from 44.1 kHz to 48 kHz.
We run again the following command:
In the grahpical interface, we navigate to Filesystem Packages → multimedia → alsa-plugins and enable alsa-plugins.
Building our PetaLinux project
After we made all the necessary modifications to our project, we can start to build it by running the following command:
This may again take a couple of hours.
Creating the boot files
When the build is finished, we can create the boot files like we did earlier.
The command to create the boot files is slightly different in PetaLinux 2023.2:
petalinux-package --boot --fsbl images/linux/zynqmp_fsbl.elf --fpga images/linux/system.bit --pmufw images/linux/pmufw.elf --u-boot
The command to create a wic-image file is also slightly different:
Booting the system
We can insert the SD card into our Ultra96v2 and power on the system. If everything goes smoothly, the system will boot, and we’ll need to log in using the username petalinux and a password of our choosing. To avoid any confusion, it may be a good idea to set the password to match the username.