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SiFive Freedom E SDK README

This repository, maintained by SiFive Inc, makes it easy to get started developing software for the Freedom E and Freedom S Embedded RISC-V Platforms. This SDK is intended to work on any target supported by SiFive's distributions of the RISC-V GNU Toolchain.

Documentation for Freedom E SDK is available here

Freedom E SDK was recently transitioned to using the Freedom Metal compatibility library. If you're looking for the old Freedom E SDK, software examples, and board support files, you can find those on the v1_0 branch.

What is Freedom Metal?

Freedom Metal (Documentation) is a library developed by SiFive for writing portable software for all of SiFive's RISC-V IP, RISC-V FPGA evaluation images, and development boards. Programs written against the Freedom Metal API are intended to build and run for all SiFive RISC-V targets. This makes Freedom Metal suitable for writing portable tests, bare metal application programming, and as a hardware abstraction layer for porting operating systems to RISC-V.


Freedom Metal Compatibility Library

  • Board Support Packages (found under bsp/)
    • Supported Targets:
    • The board support files for the Freedom Metal library are located entirely within a single target directory in bsp/<target>/. For example, the HiFive 1 board support files for Freedom Metal are entirely within bsp/sifive-hifive1/ and consist of the following:
      • design.dts, core.dts
        • The DeviceTree description of the target. This file is used to parameterize the Freedom Metal library to the target device. Modifications to these files are propagated to the generated files by freedom-devicetree-tools.
      • metal.h, metal-inline.h
        • The Freedom Metal machine headers are generated files which are used internally to Freedom Metal to instantiate structures to support the target device.
      • metal-platform.h
        • The Freedom Metal platform header provides a list of C proprocessor definitions which are used by Freedom Metal to indicate the presence of devices and provide the memory-mapped register interface for each device. The contents of this header is considered public API surface of the Metal library and can be used in applications by including metal/machine/platform.h.
        • Generated linker scripts for the target. The different scripts allow for different memory configurations.
      • openocd.cfg (for development board and FPGA targets)
        • Used to configure OpenOCD for flashing and debugging the target device.
        • Includes a variety of parameters which affect the build system for the target, including the RISC-V ISA string, the selected ABI, the code model, and more.
  • FreeRTOS (found under FreeRTOS-metal/):
    • A class of RTOS that is designed to be small enough to run on a microcontroller
    • Provided here under its own license
  • A Few Example Programs (found under software/)
    • empty
      • An empty project. Serves as a good starting point for your own program.
    • hello
      • Prints "Hello, World!" to stdout, if a serial device is present on the target.
    • sifive-welcome
      • Prints a welcome message and interacts with the LEDs.
    • return-pass
      • Returns status code 0 indicating program success.
    • return-fail
      • Returns status code 1 indicating program failure.
    • example-itim
      • Demonstrates how to statically link application code into the Instruction Tightly Integrated Memory (ITIM) if an ITIM is present on the target.
    • software-interrupt
      • Demonstrates how to register a handler for and trigger a software interrupt
    • timer-interrupt
      • Demonstrates how to register a handler for and trigger a timer interrupt
    • local-interrupt
      • Demonstrates how to register a handler for and trigger a local interrupt
    • example-pmp
      • Demonstrates how to configure a Physical Memory Protection (PMP) region
    • example-spi
      • Demonstrates how to use the SPI API to transfer bytes to a peripheral
    • dhrystone
      • "Dhrystone" Benchmark Program by Reinhold P. Weicker
    • coremark
      • "CoreMark" Benchmark Program that measures the performance of embedded microcrontrollers (MCU)
    • cflush
      • A simple example demo how to use cflush (Data) L1 and use FENCE to ensure flush complete.
    • example-rtc
      • Demonstrates how to use the RTC API to start a Real-Time Clock, set a compare value, and handle an interrupt when the clock matches the compare value.
    • example-watchdog
      • Demonstrates how to use the Watchdog API to set a watchdog timer to trigger an interrupt on timeout.
    • example-user-mode
      • Demonstrates how to drop to user mode privilege level.
    • example-user-syscall
      • Demonstrates how to register a handler for the "syscall from user mode" exception, drop to the user mode privilege level, and then issue a syscall.
    • plic-interrupts
      • A simple example demonstrating how PLIC interrupts get uses on an Arty board.
    • test-coreip
      • Assembly test code which executes instructions and checks for expected results. The tests are designed to work on SiFive CPU designs in RTL simulation or on the Arty FPGA board.
    • clic-vector-interrupts
      • A simple example demonstrating how to use CLIC non vector interrupts
    • clic-selective-vector-interrupts
      • A simple example demonstrating how to use CLIC selective vector interrupts
    • clic-hardware-vector-interrupts
      • A simple example demonstrating the use of CLIC hardware vector interrupts
    • minimal-boot
      • Demonstrates how to replace the Metal constructors and replace them with your own
    • atomics
      • Demonstrates how to use the Metal Atomic API to leverage the RISC-V atomic instruction set.
    • example-i2c
      • Demonstrates usage of the I2C API to communicate with I2C slaves.
    • example-pwm
      • Demonstrates usage of the PWM API to generate waveforms.
    • mem-latency
      • A memory test that measure the latency at different cache layers and memory blocks
    • example-hpm
      • Demonstrates usage of the RISC-V hardware performance counter APIs.
    • example-l2pm
      • Demonstrates usage of Sifive L2 performance monitor counter APIs to capture L2 cache event logs.
    • example-l2pf
      • Example for usage and measuring effectiveness of SiFive L2 Prefetcher.
    • example-lim
      • Demonstrates how to designate a function to be linked into the LIM (Loosely-Integrated Memory).
    • example-freertos-minimal
      • A simple FreeRTOS skeleton to build your FreeRTOS application.
    • example-freertos-blinky
      • A simple FreeRTOS blinky application.

Setting up the SDK


To use this SDK, you will need the following software available on your machine:

  • GNU Make
  • Git
  • RISC-V GNU Toolchain
  • RISC-V QEMU 4.1.0 (for use with the qemu-sifive-* simulation targets)
  • RISC-V OpenOCD (for use with development board and FPGA targets)
  • Segger J-LINK (for use with certain development boards)
  • Python >= 3.5
  • Python Virtualenv
  • Python Pip

Details on installing the RISC-V and Segger software follow.

Install the RISC-V Toolchain and OpenOCD

The RISC-V GNU Toolchain and OpenOCD are available from the SiFive Website at

For OpenOCD and/or RISC-V GNU Toolchain, download the .tar.gz for your platform, and unpack it to your desired location. Then, use the RISCV_PATH and RISCV_OPENOCD_PATH variables when using the tools:

cp openocd-<date>-<platform>.tar.gz /my/desired/location/
cp riscv64-unknown-elf-gcc-<date>-<platform>.tar.gz /my/desired/location
cd /my/desired/location
tar -xvf openocd-<date>-<platform>.tar.gz
tar -xvf riscv64-unknown-elf-gcc-<date>-<platform>.tar.gz
export RISCV_OPENOCD_PATH=/my/desired/location/openocd
export RISCV_PATH=/my/desired/location/riscv64-unknown-elf-gcc-<date>-<version>
Install RISC-V QEMU 4.1.0

The RISC-V QEMU Emulator is available from the SiFive Website at

Download the .tar.gz for your platform and unpack it to your desired location. Then, add QEMU to your path:

cp riscv-qemu-<version>-<date>-<platform>.tar.gz /my/desired/location
tar -xvf riscv-qemu-<version>-<date>-<platform>.tar.gz
export PATH=$PATH:/my/desired/location/riscv-qemu-<version>-<date>-<platform>/bin
Install Segger J-Link Software

Some targets supported by Freedom E SDK (like the SiFive HiFive1 Rev B) use Segger J-Link OB for programming and debugging. If you intend to use these targets, install the Segger J-Link Software and Documentation Pack for your machine:

Segger J-Link Software Downloads

Cloning the Repository

This repository can be cloned by running the following commands:

git clone --recursive
cd freedom-e-sdk

The --recursive option is required to clone the git submodules included in the repository. If at first you omit the --recursive option, you can achieve the same effect by updating submodules using the command:

git submodule update --init --recursive

Updating your SDK

If you'd like to update your SDK to the latest version:

git pull origin master
git submodule update --init --recursive


Freedom E SDK includes a number of Python scripts used during the build process to parameterize the build of Freedom Metal to the target. The dependencies of these scripts are tracked in requirements.txt. Freedom E SDK manages its own virtualenv, but there are some options which allow users to configure the virtualenv to best suit your needs.

Predownloading Python Dependencies

By default, Freedom E SDK will download Python packages from the Python Package Index when it creates the virtualenv. If you prefer to download dependencies ahead-of-time, you can run

make pip-cache

to download all Python packages. This mechanism downloads all of the dependencies pre-compiled for all platforms and Python versions supported by Freedom E SDK, so if you're trying to bring up Freedom E SDK on a system without an internet connection you can create the "pip cache" and then copy it to the connectionless machine with Freedom E SDK.

The location of the "pip cache" can be controlled with the environment variable FREEDOM_E_SDK_PIP_CACHE_PATH

export FREEDOM_E_SDK_PIP_CACHE_PATH=/path/to/pip-cache

Virtualenv Location

By default, the virtualenv is created in the venv folder at the root of Freedom E SDK. To change the location of the virtualenv, set the environment variable FREEDOM_E_SDK_VENV_PATH

export FREEDOM_E_SDK_VENV_PATH=/path/to/venv

Using the Tools

Building an Example

To compile a bare-metal RISC-V program:

make [PROGRAM=hello] [TARGET=freedom-e310-arty] [CONFIGURATION=debug] software

The square brackets in the above command indicate optional parameters for the Make invocation. As you can see, the default values of these parameters tell the build script to build the hello example for the freedom-e310-arty target with the debug configuration. If, for example, you wished to build the timer-interrupt example for the S51 Arty FPGA Evaluation target, with the release configuration, you would instead run the command

make PROGRAM=timer-interrupt TARGET=coreip-s51-arty CONFIGURATION=release software
Building an Benchmark Program

Building a benchmark program is slightly special in that certain section is required to be loaded in specific memory region. A specialize linker file has been created for its optimal run.

make PROGRAM=dhrystone TARGET=coreip-e31-arty LINK_TARGET=ramrodata software
Building an Example with FreeRTOS

A link target exist specificly for freertos, even if default target might work on some examples. Here is an exemple of use :

make PROGRAM=example-freertos-blinky-pmp TARGET=sifive-hifive1-revb LINK_TARGET=freertos software

Uploading to the Target Board

make [PROGRAM=hello] [TARGET=sifive-hifive1] [CONFIGURATION=debug] upload

Debugging a Target Program

make [PROGRAM=hello] [TARGET=sifive-hifive1] [CONFIGURATION=debug] debug

Cleaning a Target Program Build Directory

make [PROGRAM=hello] [TARGET=sifive-hifive1] [CONFIGURATION=debug] clean

Create a Standalone Project

You can export a program to a standalone project directory using the standalone target. The resulting project will be locked to a specific TARGET. Note that this functionality is only supported for Freedom Metal programs, not the Legacy Freedom E SDK.

STANDALONE_DEST is a required argument to provide the desired project location.

make [PROGRAM=hello] [TARGET=sifive-hifive1] [INCLUDE_METAL_SOURCES=1] STANDALONE_DEST=/path/to/desired/location standalone

Run make help for more commands.

For More Information

Documentation, Forums, and much more available at