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Elements Zephyr

Elements is fully integrated into Zephyr's meta-tool West and aims to provide RISC-V designs to developers without deep knowledge about hardware design. Therefore, extra commands were added to West to generate, synthesize, and simulate designs.

Prerequisites

  • Linux host system (Ubuntu 22.04 recommended)
  • Python 3 (python3.10-dev)
  • Vivado for Xilinx platforms (optional)

Installation

  • Install required packages:

    sudo apt install ssh git curl libtool-bin autotools-dev automake pkg-config libyaml-dev
sudo apt install libssl-dev gdb ninja-build flex bison libfl-dev cmake libftdi1-dev
sudo apt install python3 python3.10-dev python3-pip virtualenv openjdk-11-jdk-headless
sudo apt install verilator gtkwave libcanberra-gtk-module libcanberra-gtk3-module
sudo apt install libtinfo5 libncurses5 libboost-all-dev

  • Install sbt:

    echo "deb https://repo.scala-sbt.org/scalasbt/debian all main" | sudo tee /etc/apt/sources.list.d/sbt.list
echo "deb https://repo.scala-sbt.org/scalasbt/debian /" | sudo tee /etc/apt/sources.list.d/sbt_old.list
curl -sL "https://keyserver.ubuntu.com/pks/lookup?op=get&search=0x2EE0EA64E40A89B84B2DF73499E82A75642AC823" | sudo -H gpg --no-default-keyring --keyring gnupg-ring:/etc/apt/trusted.gpg.d/scalasbt-release.gpg --import
sudo chmod 644 /etc/apt/trusted.gpg.d/scalasbt-release.gpg
sudo apt update
sudo apt install sbt

  • Download and build all components:

    chmod +x init.sh
./init.sh

Afterwards, everything should be installed and west can be used to generate RISC-V designs.

Vivado

The Vivado toolchain is not part of this SDK and needs to be installed separately for Xilinx platforms from Xilinx's homepage. Download the Linux Self Extracting Web Installer for Version 2022.2 and install it. Select Vivado as product and Vivado HL WebPACK as Edition. You can use this edition's license for free if you do not sell the bitstream, and disable everything except the Artix-7 Platform to save disk storage. Elements except to find the Vivado toolchain under /opt/xilinx.

chmod +x ~/Downloads/Xilinx_Unified_2022.2_1014_8888_Lin64.bin
~/Downloads/Xilinx_Unified_2022.2_1014_8888_Lin64.bin

Docker

The Elements SDK supports running inside Docker. Currently, only self-build images can be used.

Custom Image

A Docker Compose configuration is provided for systems that do not run with the recommended versions. The Docker will have included all required packages for the SDK, except vendor toolchains. Build the image (which can take some minutes).

docker-compose build

Next, start the Docker in the background.

docker-compose up -d

Afterwards, west can be used identical to the CLI.

sudo docker exec -it elements-sdk_zephyr_1 west build -p always -b helium1-ecpix5 \
    elements-zephyr-samples/demo/leds/

Finally, stop the Docker.

docker-compose stop

Development

The docker image can also be used to develop. Therefore, the repos on the host system should be forwarded to the container to make all changes public. Open the docker-compose.yml file and uncomment the lines in volumes which should be made public.

Afterwards, go into zephyr/ and download Zephyr with all repositories.

chmod +x init.sh
.init.sh -z

GUI Support

Some GUI applications require access to the host system's X server. Run the following command in the host shell to grant them.

xhost local:root

Support

The following boards are supported with this version.

Board Elements SoC FPGA Board Vendor FPGA Chip
helium1-ecpix5 Helium1 ECPIX-5 LambdaConcept ECP5
helium1-nexysa7 Helium1 Nexys A7 Digilent Artix-7
neon1-ecpix5 Neon1 ECPIX-5 LambdaConcept ECP5
neon1-nexysa7 Neon1 Nexys A7 Digilent Artix-7
argon1-ecpix5 Argon1 ECPIX-5 LambdaConcept ECP5

Usage

Elements is fully integrated into the Zephyr west development process. Simply build software for a Elements board. Afterwards, the build cache contains enough information to synthesize the design.

west build -p always -b helium1-ecpix5 elements-zephyr-samples/demo/leds/
west synthesize
west flash

Run flash with the --spi` argument to flash the bitstream into the SPI flash.

west flash --spi

Additionally, a design can only be generated instead of synthesized to inspect the generated Verilog code.

west build -p always -b helium1-ecpix5 elements-zephyr-samples/demo/leds/
west generate

Lastly, a design can be simulated and viewed with GTKWave.

west build -p always -b helium1-ecpix5 elements-zephyr-samples/demo/leds/
west simulate

Flash SPI-Nor Flash

Pad the Zephyr binary because flashrom can't handle images which not align with pages.

dd if=/dev/zero of=flash.bin bs=1MiB count=32
dd if=build/zephyr/zephyr.bin of=flash.bin conv=notrunc

Use a bus pirate to flash the padded Zephyr image to the SPI-Nor flash.

Known Issues

  • west debug only works with bitstreams synthesized with Vivado.
  • F4PGA does not support PLLs on Xilinx architectures right now.
  • PLLs are not working on the ECPIX-5 board when the bitstream gets loaded from the flash.

License

Copyright (c) 2024 aesc silicon. Released under the MIT license.