IOb-SoC

IOb-SoC is a System-on-Chip (SoC) template comprising an open-source RISC-V processor (picorv32), an internal SRAM memory subsystem, a UART, and an optional interface to external memory. If the external memory interface is selected, an instruction L1 cache, a data L1 cache, and a shared L2 cache are added to the system. The L2 cache communicates with a 3rd party memory controller IP (typically a DDR controller) using an AXI4 master bus.

Nix environment

You can use nix-shell to run IOb-SoC in a Nix environment with all dependencies available except for Vivado and Quartus for FPGA compilation and running.

After installing nix-shell, it can be initialized by calling any Makefile target in the IOb-SoC root directory, for example

make setup

The first time it runs, nix-shell will automatically install all the required dependencies. This can take a couple of hours, but after that, you can enjoy IOb-SoC and not worry about installing software tools.

Dependencies

If you prefer, you may install all the dependencies manually and run IOb-SoC without nix-shell. The following tools should be installed:

• GNU Bash >=5.1.16
• GNU Make >=4.3
• RISC-V GNU Compiler Toolchain =2022.06.10 (Instructions at the end of this README)
• Python3 >=3.10.6
• Python3-Parse >=1.19.0

Optional tools, depending on the desired run strategy:

• Icarus Verilog >=10.3
• Verilator >=5.002
• gtkwave >=3.3.113
• Vivado >=2020.2
• Quartus >=20.1

Older versions of the dependencies above may work but still need to be tested.

Operating Systems

IOb-SoC can be used in Linux Operating Systems. The following instructions work for CentOS 7 and Ubuntu 18.04, 20.04, and 22.04 LTS.

Clone the repository

The first step is to clone this repository. IOb-SoC uses git sub-module trees, and GitHub will ask for your password for each downloaded module if you clone it by https. To avoid this, setup GitHub access with ssh and type:

git clone --recursive [email protected]:IObundle/iob-soc.git
cd iob-soc

Alternatively, you can still clone this repository using https if you cache your credentials before cloning the repository, using: git config --global credential.helper 'cache --timeout=<time_in_seconds>'

Configure your SoC

To configure your system, edit the iob_soc.py file, which can be found at the repository root. This file has the system configuration variables; hopefully, each variable is explained by a comment.

Set environment variables for local or remote building and running

The various simulators, FPGA compilers, and FPGA boards may run locally or remotely. For running a tool remotely, you need to set two environmental variables: the server logical name and the server user name. Consider placing these settings in your .bashrc file so that they apply to every session.

Set up the remote simulator server

Using the open-source simulator Icarus Verilog (iverilog) as an example, note that in submodules/hardware/simulation/icarus.mk, the variable for the server logical name, SIM_SERVER, is set to IVSIM_SERVER, and the variable for the user name, SIM_USER is set to IVSIM_USER.

To run the simulator on the server mysimserver.myorg.com as user ivsimuser, set the following environmental variables beforehand, or place them in your .bashrc file:

export IVSIM_SERVER=ivsimserver.myorg.com
export IVSIM_USER=ivsimuser

When you start the simulation, IOb-SoC's simulation Makefile will log you on to the server using ssh, then rsync the files to a remote build directory and run the simulation there. If you do not set these variables, the simulator will run locally if installed.

Set up the remote FPGA toolchain and board servers

Using the CYCLONEV-GT-DK board as an example, note that in hardware/fpga/quartus/CYCLONEV-GT-DK/Makefile, the variable for the FPGA tool server logical name, FPGA_SERVER, is set to QUARTUS_SERVER, and the variable for the user name, FPGA_USER, is set to QUARTUS_USER; the variable for the board server, BOARD_SERVER, is set to CYC5_SERVER, and the variable for the board user, BOARD_USER, is set to CYC5_USER. As in the previous example, set these variables as follows:

export QUARTUS_SERVER=quartusserver.myorg.com
export QUARTUS_USER=quartususer
export CYC5_SERVER=cyc5server.myorg.com
export CYC5_USER=cyc5username

In each remote server, the environment variable for the license server used must be defined as in the following example:

export [email protected];lic_or_dat_file

Create the build directory

IOb-SoC uses intricate Python scripting to create a build directory with all the necessary files and makefiles to run the different tools. The build directory is placed in the folder above at ../iob_soc_Vx.y by running the following command from the root directory.

make setup

If you want to avoid getting into the complications of our Python scripts, use the ../iob_soc_Vx.y directory to build your SoC. It only has code files and a few Makefiles. Enter this directory and call the available Makefile targets. Alternatively, using another Makefile in the IOb-SoC root directory, the same targets can be called. For example, to run the simulation, the IOb-SoC's top Makefile has the following target:

sim-run:
	nix-shell --run 'make clean setup INIT_MEM=$(INIT_MEM) USE_EXTMEM=$(USE_EXTMEM) && make -C ../$(CORE)_V*/ sim-run SIMULATOR=$(SIMULATOR)'

The above target invokes the nix-shell environment to call the local targets clean and setup and the target sim-run in the build directory. Below, the targets available in IOb-SoC's top Makefile are explained.

Emulate the system on PC

You can emulate IOb-SoC's on a PC to develop and debug your embedded system. There is also a model to emulate the UART, which communicates with a run-time Python script server. If you develop peripherals, you can build embedded software models to run them using PC emulation. To emulate IOb-SoC's embedded software on a PC, type:

make pc-emul-run

The Makefile compiles and runs the software in the ../iob_soc_Vx.y/software/ directory. The Makefile includes the sw_build.mk segment supplied initially in the ./software/ directory in the IOb-SoC root. Please feel free to change this file for your specific project. To run an emulation test comparing the result to the expected result, run

make pc-emul-test

Simulate the system

To simulate IOb-SoC's RTL using a Verilog simulator, run

make sim-run [SIMULATOR=icarus!verilator|xcelium|vcs|questa] [INIT_MEM=0|1] [USE_EXTMEM=0|1]

The INIT_MEM variable specifies whether the firmware is initially loaded in the memory, skipping the boot process, and the USE_EXTMEM variable indicates whether an external memory such as DRAM is used, in which case the cache system described above is instantiated.

The Makefile compiles and runs the software in the ../iob_soc_Vx.y/hardware/simulation directory. The Makefile includes the ./hardware/simulation/sim_build.mk, which you can change for your project. To run a simulation test comprising several simulations with different parameters, run

make sim-test

The simulation test contents can be edited in IOb-SoC's top Makefile.

Each simulator must be described in the ./submodules/LIB/hardware/simulation/<simulator>.mk file. For example, the file vcs.mk describes the VCS simulator.

The host machine must run an access server, a Python program in ./submodules/LIB/scripts/board_server.py, set up to run as a service. The client connects to the host using the SSH protocol and runs the board client program /submodules/LIB/scripts/board_client.py. Note that the term board is used instead of simulator because the same server/client programs control the access to the board and FPGA compilers. The client requests the simulator for GRAB_TIMEOUT seconds, which is 300 seconds by default. Its value can be specified in the ./hardware/fpga/fpga_build.mk Makefile segment, for example, as

GRAB_TIMEOUT ?= 3600

Build and run on FPGA board

To build and run IOb-SoC on an FPGA board, the FPGA design tools must be installed locally or remotely. The FPGA board must also be attached to the local or remote host, not necessarily the same host where the design tools are installed.

Each board must be described under the /submodules/LIB/hardware/fpga/<tool>/<board_dir> directory. For example, the hardware/fpga/vivado/BASYS3 directory contents describe the board BASYS3, which has an FPGA device that can be programmed by the Xilinx/AMD Vivado design tool. The access to the board is controlled by the same server/client programs described above for the simulators. To build an FPGA design of an IOb-SoC system and run it on the board located in the board_dir directory, type

make fpga-run [BOARD=<board_dir>] [INIT_MEM=0|1] [USE_EXTMEM=0|1]

To run an FPGA test comparing the result to the expected result, run

make fpga-test

The FPGA test contents can be edited in IOb-SoC's top Makefile.

Compile the documentation

To compile documents, the LaTeX software must be installed. Three document types are generated: the Product Brief (pb), the User Guide (ug), and a presentation. To build a given document type DOC, run

make doc-build [DOC=pb|ug|presentation]

To generate the three documents as a test, run

make doc-test

Total test

To run all simulation, FPGA board, and documentation tests, type:

make test-all

Running more Makefile Targets

The examples above are the Makefile targets at IOb-SoC's root directory that call the targets in the top Makefile in the build directory. Please explore the available targets in the build directory's top Makefile to add more targets to the root directory Makefile.

Cleaning the build directory

To clean the build directory, run

make clean

Instructions for Installing the RISC-V GNU Compiler Toolchain

Get sources and check out the supported stable version

git clone https://github.com/riscv/riscv-gnu-toolchain
cd riscv-gnu-toolchain
git checkout 2022.06.10

Prerequisites

For the Ubuntu OS and its variants:

sudo apt install autoconf automake autotools-dev curl python3 python2 libmpc-dev libmpfr-dev libgmp-dev gawk build-essential bison flex texinfo gperf libtool patchutils bc zlib1g-dev libexpat-dev

For CentOS and its variants:

sudo yum install autoconf automake python3 python2 libmpc-devel mpfr-devel gmp-devel gawk  bison flex texinfo patchutils gcc gcc-c++ zlib-devel expat-devel

Installation

./configure --prefix=/path/to/riscv --enable-multilib
sudo make -j$(nproc)

This will take a while. After it is done, type:

export PATH=$PATH:/path/to/riscv/bin

The above command should be added to your ~/.bashrc file so you do not have to type it on every session.