Ming Sun – Silicon achitect, design lead, researcher.

Introduction^[1]

XSCHEM : schematic capture and netlisting EDA tool^[1]

Xschem is a schematic capture program, it allows creation of hierarchical representation of circuits with a top down approach . By focusing on interfaces, hierarchy and instance properties a complex system can be described in terms of simpler building blocks. A VHDL or Verilog or Spice netlist can be generated from the drawn schematic, allowing the simulation of the circuit. Key feature of the program is its drawing engine written in C and using directly the Xlib drawing primitives; this gives very good speed performance, even on very big circuits. The user interface is built with the Tcl-Tk toolkit, tcl is also the extension language used^[1].

Histroy^[1]

1998First draft.

2004First release.

2016Second release, uploading on sourceforge.

20202.9.5 release, uploading on repo.hu and sourceforge.

20212.9.9 release, skywater 130nm pdk integration.

20213.0.0 release, now including windows binary distribution.

20223.1.0 release, ability to display simulation graphs and embeded images/logos.

Step 1 - install Ubuntu

First, we need to install Ubuntu on to your system. In my case, I use Parallels Desktop^[2] to install Ubuntu.

Fig. 1Install Ubuntu with Parallels Desktop^[2]

Please change the Ubuntu hardware disk space setting in Parallels Desktop from 64GB to 128GB so that we have enough disk space to install Xschem, Magic, Skywater130 PDK and Ngspice.

To do so, we have to shutdown Ubuntu first by going to Control Center of Parallels Desktop. Right click and then choose Configure.

Fig. 2Control center of Parallels Desktop^[2]

Next, Choose Hard Disk => Advanced... => Properties... => Change size to 128GB => click Apply.

Fig. 3Change Ubuntu disk size to 128GB^[2]

Then at Control Center, start up Ubuntu again.

Step 2 - install Xschem

If you do not have git installed, we can use the following command to install git in the Ubuntu system.

sudo apt-get update
sudo apt-get upgrade
sudo apt-get install git-all

Next, we can follow the procedure as mentioned in Ref. 3~4. First we clone the Xschem from GitHub repo.

git clone https://github.com/StefanSchippers/xschem.git xschem-git

Then cd to the xschem-git folder.

cd xschem-git

Please make sure we have the following packages installed:

sudo apt-get install libx11-6
sudo apt-get install libx11-dev
sudo apt-get install libxrender1
sudo apt-get install libxrender-dev
sudo apt-get install libxcb1
sudo apt-get install libx11-xcb-dev
sudo apt-get install libcairo2
sudo apt-get install libcairo2-dev
sudo apt-get install tcl8.6
sudo apt-get install tcl8.6-dev
sudo apt-get install tk8.6
sudo apt-get install tk8.6-dev
sudo apt-get install flex
sudo apt-get install bison
sudo apt-get install libxpm4
sudo apt-get install libxpm-dev
sudo apt-get install gawk
sudo apt-get install mawk
sudo apt-get install tcl-tclreadline
sudo apt-get install xterm

Next, try configure command to check if we have the necessary packages installed in the Ubuntu system.

./configure

Next, we need to become to the root so that the Xschem can be installed at /usr/local path. To do so, we can try the following command:

sudo -i
cd /home/parallels/Desktop/xschem-git

After you became root, we need to go to the xschem-git folder. In my case, here is the path /home/parallels/Desktop/xschem-git.

Next we can try the following command to install Xschem.

make
make install

If you would like your simulation folder to be at your local instead of the system root path, you can do so:

cp -r .xschem/ /home/parallels

After the Xschem is installed, we can type xschem in the terminal to start the Xschem.

Fig. 4Xschem user interface^[5]

Step 3 - install Magic

First, clone Magic from Git Repo.

cd /home/parallels/Desktop
git clone git://opencircuitdesign.com/magic
cd magic

Next, install the necessary packages:

sudo apt-get install m4
sudo apt-get install tcsh
sudo apt-get install csh
sudo apt-get install libx11-dev
sudo apt-get install tcl-dev tk-dev
sudo apt-get install libcairo2-dev
sudo apt-get install mesa-common-dev libglu1-mesa-dev
sudo apt-get install libncurses-dev

After the necessary packages are installed, we can install Magic.

./configure
make
make install

After the installation, you can type magic in the terminal window to see if you can start the Magic software. If so, Magic has been successfully installed.

Step 4 - install Skywater130 PDK^[5-6]

At your home directory, enter the following command. At a minimum, initialize the first four submodules (io, pr, sc_hd, and sc_hvl). These comprise the I/O pad cells, the primitive devices, the high-density digital standard cells, and the high-voltage digital standard cells.

cd /home/parallels/Desktop
git clone https://github.com/google/skywater-pdk
cd skywater-pdk
git submodule init libraries/sky130_fd_io/latest
git submodule init libraries/sky130_fd_pr/latest
git submodule init libraries/sky130_fd_sc_hd/latest
git submodule init libraries/sky130_fd_sc_hdll/latest

# optional -----------
git submodule init libraries/sky130_fd_sc_hs/latest
git submodule init libraries/sky130_fd_sc_ms/latest
git submodule init libraries/sky130_fd_sc_ls/latest
git submodule init libraries/sky130_fd_sc_lp/latest
git submodule init libraries/sky130_fd_sc_hvl/latest
# --------------------

# You can skip the above optional command. But the following two commands must be run.
git submodule update
make timing

Step 5 - install Open_PDKs^[7]

First, download Open_PDKs.

cd /home/parallels/Desktop
git clone git://opencircuitdesign.com/open_pdks
cd open_pdks

Next, we try the following configure command. Notice that here we need to specify the Skywater130 PDK path. In my case, it is /home/parallels/Desktop/skywater-pdk.

./configure --enable-sky130-pdk=/home/parallels/Desktop/skywater-pdk

If the configure is successful, we can run the following command to install Open_PDKs.

make
make install

Step 6 - install Ngspice^[4]

The following packages might be needed to be installed on your system.

sudo apt-get install adms
sudo apt-get install autoconf
sudo apt-get install libtool
sudo apt-get install libxaw7-dev
sudo apt-get install build-essential
sudo apt-get install libc6-dev
sudo apt update
sudo apt upgrade
sudo apt-get install manpages-dev man-db manpages-posix-dev
sudo apt-get install libreadline6-dev
sudo apt-get update -y

Next, download Ngspice from its git repo.

cd /home/parallels/Desktop
git clone https://github.com/ngspice/ngspice.git
cd ngspice
./autogen.sh --adms

Then, create release folder.

mkdir release
cd release

Configure and install Ngspice.

../configure  --with-x --with-readline=yes --disable-debug
make
sudo make install

After Ngspice is installed, go to Xschem simulation folder, in my case it is /home/parallels/.xschem/simulations. At this folder, create a .spiceinit file with the following content.

.spiceinit

set ngbehavior=hs

Step 6 - verify Xschem and Ngspice through the simulation example

Close the terminal where you are root. Then open a new terminal. I would like my projects to be at my local Desktop.

cd
cd Desktop
mkdir projects
cd projects
cp /usr/local/share/pdk/sky130A/libs.tech/xschem/xschemrc /home/parallels/Desktop/projects
xschem

The above command basically copy Xschem configuration file xschemrc to the projects folder where we start Xschem.

After xschem command is entered in the terminal, Xschem shall be started with the following content as shown in Fig. 5.

Fig. 5Xschem startup screen^[4]

Then zoom in to the left side using the hot key shift+z. Click test_pmos and press hot key e to enter.

Fig. 6test_pmos schematic^[4]

On the top right, click Netlist and then click Simulate. The Ngspice window shall pop up as shown in Fig. 7.

Fig. 7Ngspice pop up window^[4]

If you would like to use gaw to view the waveform, you have to install gaw package. You can also load the waveform without a third party waveform viewer by clicking Simulation => Load/Unload spice .raw file.

Fig. 8Simulation results^[4]

Summary

I am not an expert of Ubuntu. It takes me about two days to finally install Xschem, Ngspice, Skywater130 PDK into the Ubuntu installed through Parallels Desktop on my Mac.

The above blog post may not capture all the details and problems I have encountered during the installation. For example, I first use Ref. [4] to install Xschem, and finally find out that part of the video is out dated. So I switch to use Ref. [6]. During the installation, Ubuntu complains the disk is full. So I deleted the entire Ubuntu from Parallels Desktop and start over again.

This time, I only initialized the first four submodule instead (io, pr, sc_hd, and sc_hvl) instead.

Please use Google to solve the problem and find out which dependencies you need to install during the installation. Eventually, you will get there!

Installation of EDA and PDKs is not fun 😔. But after you struggling with the installation, we will eventually arrive at the fun part - Circuits!

Enjoy!😊