In the final part of the Arty base project tutorial, we build a PetaLinux project that’s tailored to our Arty base design. Then we boot PetaLinux on our hardware and verify that we have network connectivity by checking the Arty’s DHCP assigned IP address and then pinging it from a PC.
I used the following setup to do this project:
Vivado project modifications
Before we get started with PetaLinux, we have to make sure that our Vivado design satisfies the minimum requirements for running PetaLinux:
- Microblaze must use configuration “Linux with MMU” or “Low-end Linux with MMU“
- At least 32MB of external memory
- Dual channel timer with interrupt connected
- UART IP with interrupt connected
- Ethernet IP with interrupt connected
Our original base design satisfies all but one of those requirements – the first one. So the first thing we have to do in this tutorial is to select the “Linux with MMU” configuration for the Microblaze. The next thing we do is to enable the GPIO interrupts and connect them through to the Microblaze – this isn’t a requirement, but it’s useful. We then have to save our block design, re-generate a bitstream for the project and export it.
PetaLinux tool commands
To build the PetaLinux project, we transfer our entire Vivado project to a Linux machine with the PetaLinux tools installed. These are the PetaLinux tool commands that we use in the tutorial, in the order that we use them:
# Launch PetaLinux tools (note that you'll have to specify your own PetaLinux install path) source ./PetaLinux-2017-3/settings.sh # Cd to the working directory (where the arty_base directory has been copied to) cd /media/opsero/arty # Create the PetaLinux project, using the "microblaze" template petalinux-create --type project --template microblaze --name arty_petalinux # Cd to the PetaLinux project cd arty_petalinux # Import the hardware description into our PetaLinux project petalinux-config --get-hw-description ../arty_base/arty_base.sdk --oldconfig # Optional: Configure the kernel petalinux-config -c kernel # Optional: Configure the root filesystem petalinux-config -c rootfs # Build the PetaLinux project petalinux-build
The Linux driver for the AXI Ethernetlite IP requires certain drivers to be enabled in the PetaLinux kernel. Fortunately, the PetaLinux tools are pretty good at enabling the drivers for the IP that it finds in your exported Vivado design. So the required drivers are already enabled and we don’t have to run the kernel configuration (petalinux-config -c kernel), but for completeness, here is a list of the required kernel configurations:
Device tree modification
We have to make an addition to the device tree in order to specify the Ethernet PHY’s address with respect to the MDIO bus. This address depends on how the PHY is physically wired, for any particular board it is usually mentioned in the user guide or if not we can usually figure it out from the schematics. In the case of the Arty, the PHY address is 1 (one) and we need to specify this in the device tree so that the Ethernet driver can communicate with the PHY. Below is the device tree code that we need to add to the system-user.dtsi file.
Launching it on the Arty
Once the PetaLinux project is built, we then launch the Putty UART console and program the FPGA with bitstream and kernel. Here are the commands we used:
# Launch Putty, the UART console sudo putty & # Program the FPGA with the bitstream petalinux-boot --jtag --fpga # Load the kernel into memory and run it petalinux-boot --jtag --kernel
How to package the PetaLinux project
It’s useful to be able to program the flash with our bitstream and Linux kernel so that it boots up automatically when we power up the board. To be able to do this, we need to package the PetaLinux project and generate a .mcs file. We don’t go through this in the video, but if you’re interested, here’s how to do it:
- In the Linux command terminal, type:
Subsystem AUTO Hardware Settings->Advanced bootable images storage Settings
Subsystem AUTO Hardware Settings->Flash Settings
fpga partition size 0x300000
boot partition size 0x100000
bootenv partition size 0x100000
kernel partition size 0xA40000
petalinux-package --boot --force --fpga ../arty_base/arty_base.runs/impl_1/design_1_wrapper.bit --u-boot --kernel --flash-size 16 --flash-intf SPIx1
You’ll find the boot.mcs file under arty_petalinux/images/linux.
Try it yourself
In the compressed file, you’ll find a bitstream and .elf file (the PetaLinux kernel) that can be downloaded to your Arty via JTAG using the XMD tool. Launch XMD and type these commands:
fpga -f design_1_wrapper.bit connect mb mdm dow image.elf run
Also in the compressed file, you’ll find a .mcs file that you can program into the Arty’s flash memory so that PetaLinux boots up every time you power up the board. To program the Arty’s flash memory:
- launch the Hardware Manager in Vivado
- make a connection with the FPGA
- add configuration memory device “n25q128-3.3v-spi-x1_x2_x4“
- program the configuration memory device with the .mcs file
Digilent has a good tutorial on this here: Programming the Arty using Quad SPI Flash
Make sure to open a UART terminal for a baud rate of 9600, so that you don’t miss the boot log. Also, remember to connect the Arty to your network router so that the IP address gets automatically assigned during the boot sequence.