Zephyr on LiteX-VexRiscv

Cloning the repository

$ git clone https://github.com/antmicro/zephyr.git
$ git checkout litex-vexriscv

Building the application

Prerequisites

In order to build a sample application, the Zephyr SDK has to be installed in the system. To install the Zephyr SDK, do the following:

$ wget https://github.com/zephyrproject-rtos/meta-zephyr-sdk/releases/download/0.10.0/zephyr-sdk-0.10.0-setup.run
$ chmod +x zephyr-sdk-0.10.0-setup.run
$ ./zephyr-sdk-0.10.0-setup.run

Zephyr itself requires some additional tools to be installed in the system. Follow the Zephyr documentation for requirements.

Required python3 packages can be installed with:

$ pip3 install -r scripts/requirements.txt

Building

To build the application you need to setup a build environment. To do this, source the zephyr-env.sh file from the zephyr directory.

$ source zephyr-env.sh

Additionally, three environment variables have to be set before building the app:

$ export ZEPHYR_TOOLCHAIN_VARIANT="zephyr"
$ export ZEPHYR_SDK_INSTALL_DIR="/opt/zephyr-sdk" #assuming default sdk install directory
$ export BOARD="arty_litex_vexriscv"

The next step is to create a make environment:

$ cd samples/synchronization/
$ mkdir -p build && cd build
$ cmake ../

To build the application, simply run make:

$ make -j`nproc`

The resulting binary is located in the build/zephyr directory under zephyr.bin.

Simulation

Before running it on the hardware, the Zephyr application can be tested in simulation:

litex_sim --cpu-type=vexriscv --cpu-variant=full --ram-init=<path_to_zephyr.bin>

Binary deployment

Zephyr has been tested on system generated from the Antmicro's fork of the LiteX repository. The binary can be loaded with serial port using flterm:

flterm --port /dev/ttyUSB0 --kernel <path_to_zephyr.bin> --kernel-addr 0x40000000