Bare-metal Flow Example

Developers who wish to use SOM without Linux will be creating a bare-metal(also called standalone) application. This example flow will detail the process of creating a simple PL design with a BRAM connected to the PS, running on the Vision AI Starter Kit. The flow will then create a standalone software in Vitis to read and write from BRAM. Lastly, the flow will suggest two ways to load and test the application on SOM.

  • Assumption: AMD built carrier cards with corresponding SOM Starter Kit board file

  • Input: SOM Starter Kit board files (in Vivado), developer’s own accelerator designs in Vivado (in this case, BRAM)

  • Output: <pl>.bit, fsbl.elf, pmufw.elf, <application>.elf, and boot.bin

Prerequisites and Assumptions

This document assumes that developers will use 2021.1 or later tools and SOM content releases. The tool versions should match - e.g. use the same tool versions for Vivado, Vitis, Bootgen, XSDB

  1. Vitis tools installation, which will include Vivado, Bootgen, and XSDB

Vivado board file

This flows starts with Vivado board files containing information on K26, K24, KV260 CC, KR260 CC or KD240 CC. The K26/K24 SOM is supported in Vivado with board files that automate the configuration of the board peripherals. These board files are available in Vivado’s board list in “Create Project” wizard.

Refer to Wiki for a list of board files required, tool versions that support them and how to download them from XHUB store correctly.

Step 1: Generate PL design in Vivado

Start Vivado. Choose File -> Project -> New. Then choose RTL project:

Tool Flow

Click next, then choose boards in Default Part section, choose K26*/K24* card (in this case K26C), and then click on connections:

Tool Flow

Choose the carrier card to connect the SOM to, in this case the Vision AI Starter Kit carrier card:

Tool Flow

Click through to finish creating the project. Now create a block design:

Tool Flow

In Block Design, click on the + sign, and add PS block:

Tool Flow

Once the PS block is added, make sure to click Run Block Automation and apply the board preset. This will configure the PS block correctly for SOM + Carrier Card:

Tool Flow

Now add another block - the AXI BRAM controller:

Tool Flow

Click on Run Connection Automation and connect the S_AXI port of BRAM controller with M_AXI_HPM0 port of PS:

Tool Flow

Click on Run Connection Automation again and connect BRAM_PORTA to a block ram:

Tool Flow

Double click the BRAM controller and configure it to only have 1 BRAM interface:

Tool Flow

Double click the PS block, select ``PS-PL Configuration``` and configure it to only enable HPM0 (unselect HPM1):

Tool Flow

Now connections are complete. Click on Generate Block Design:

Tool Flow

After that is done generating, right click on the block design you have created and select Create HDL Wrapper, this will set the created block design as top module:

Tool Flow

Check the address map of the BRAM slave memory so we can use the same address in software later:

Tool Flow

Generate the bitstream:

Tool Flow

This will generate a bitstream at:


Lastly, export the .xsa file to work the next step in Vitis:

Tool Flow

Select Include bitstream:

Tool Flow

Launch Vitis by selecting Tools -> Layunch Vitis IDE:

Tool Flow

Step 2: Generate Standalone Software in Vitis

In Vitis, select Project -> Create Application Project:

Tool Flow

Select Create a new platform from hardware (XSA) and point to the .xsa file that was just exported in step 1:

Tool Flow

Name the application and associate with PSU_cortexa53_0:

Tool Flow Tool Flow

Use Hello World as a template: Tool Flow

In helloworld.c, alter the code to read and write from BRAM, and then right click hello_world_system and select Build Project:

Tool Flow

Now developers will have the following files:


Step 3: Boot Baremetal Applications

There are two ways to boot baremetal applications - using JTAG to download files and start the application, and programming boot files into boot image sectors of QSPI so that the application boots up upon power up without needing XSDB. JTAG booting is ideal for development and debugging, while QSPI booting is ideal for deployment.

Option 1: Boot using JTAG

Developers can boot using JTAG using the 4 files generated: fsbl.elf, pmufw.elf, hello_world.elf, add_bram_wrapper.bit using the following XSDB script:

proc boot_jtag { } {
# Switch to JTAG boot mode #
targets -set -filter {name =~ "PSU"}
# update multiboot to ZERO
mwr 0xffca0010 0x0
# change boot mode to JTAG
mwr 0xff5e0200 0x0100
# reset
rst -system


after 2000
targets -set -filter {name =~ "PSU"}
fpga "add_bram_wrapper.bit"
mwr 0xffca0038 0x1FF

# Download pmufw.elf
targets -set -filter {name =~ "MicroBlaze PMU"}
after 500
dow pmufw.elf
after 500

# Select A53 Core 0
targets -set -filter {name =~ "Cortex-A53 #0"}
rst -processor -clear-registers
dow fsbl.elf
after 10000

dow hello_world.elf
after 500

Option 2: Boot Using boot.bin

Alternatively, developers can generate a boot.bin file to be programmed into the A/B image update section.

Developers first need to create a <test>.bif file containing the following:

    [fsbl_config] a5x_x64


Then they need to run bootgen to create boot.bin:

bootgen -arch zynqmp -image test.bif -o boot.bin

Then, use the FW update and recovery utility documented in wiki to update the boot firmware. In this example, we have decided to write boot.bin into image A. Make sure to mark Image A as bootable, and as the requested Boot Image so that SOM will boot image A on every power cycle.

Tool Flow

Step 4: Observe UART Output

After step 3, .bit file and the .elf files will be programmed, and developers should observe printouts from uart indicating the ability to write and read from BRAM.

Optional: Restoring Linux booting image

Developers may want to restore a Starter Kit back to its default image and Linux boot FW after one of the image sectors has been overwriten with baremetal boot file. In that case, they can download the released Linux booting BOOT.bin from SOM Wiki and program it into one of the boot image sectors. They will then mark that image sector as bootable and requested image.


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