HDL Studio is a VS Code extension for simulating and synthesizing digital circuits written in Verilog/SystemVerilog. It brings the DigitalJS digital logic simulator and the yosys2digitaljs netlist format converter directly into your editor, with synthesis delegated to a native Yosys binary running in the associated dev-container.
Simulation of circuit (using DigitalJS) including support for
- Continuous simulation
- Single step
- Trigger
- Signal monitor and plotting.
Saving/backing up the circuit including the source file information in a portable format
(The relative paths of the source files are saved and so that the project can be fully
restored on another machine as long as the source files are also packaged/copied with
the project/circuit file)
The saved file can be loaded again using this extension,
or in the online version for simulation.
Open the JSON circuit saved by the online version
for simulation. Accepted extensions are either .json or .digitaljs.
.digitaljs will be opened by default using this extension.
Exporting the synthesized circuit as vector (SVG) or raster images (PNG or JPEG).
Undo and redo all the changes on the circuit including but not limited to
resynthesize of the circuit and edits done from the graphic view of the circuit.
Highlighting the source code that matches certain circuit element in the graphic view.
This can be seen in the screenshot above.
Using Lua scripts to customize/seed the simulation
(using digitaljs_lua)
Lua command line
Viewing and simulation of multiple circuits simultaneously
Zoom and pan support with both mouse and touch screen.
This extension is designed to run inside the provided dev-container, which includes a native Yosys binary. Synthesis will not work without it.
Creating and opening circuit
New circuits can be created from an empty circuit or from existing source files.
To create a new circuit, use the HDL Studio: New Circuit command
or click the HDL Studio icon next to the editor title when the current source file
isn't one recognized by HDL Studio.
To create a circuit from an existing source file (.v, .sv, .vh and .lua supported),
use the HDL Studio icon when the source file is open or click Create circuit in HDL Studio
in the context menu for the file in the explorer view.
The source file will be added to the new circuit and the new circuit will by default
inherit the name from the source file.
After the circuit is created, new files can be added to it either using the HDL Studio icon
and the explorer context menu, or using the Add Files button from the Files view
in the HDL Studio side panel.
Files with extension .digitaljs will automatically be opened by HDL Studio.
Opening files with .json is also supported using either the explorer context menu
or the Open With VS Code command. One can also open JSON files saved from
DigitalJS Online. However, since DigitalJS Online
does not save any source info, only simulation and the graphic editor are supported
on such files. Synthesis is only supported once new source files have been added.
Note that the circuit file contains relative paths to the source files.
If the circuit is to be copied to a different machine, the source files
also need to be copied with the same relative paths.
The main UI for HDL Studio includes the main circuit view/editor and three side panels.
The main circuit view shows the synthesized circuit (if one exists).
It includes interactive tools to view the circuit, edit connections,
view and plot signals, and set up triggers.
The circuit view supports zooming and panning using touch/drag, two-finger drag/pinch
as well as Ctrl + scroll wheel.
For complex circuits, the submodules can be opened in a popup window.
The three side panels show the files in the circuit, the synthesis options
and the simulation control respectively.
Synthesis
Once the source files are added, the circuit can be synthesized
using the synthesis side panel. The synthesis options can be set on the same panel
and will be saved along with the circuit.
If the source file for the circuit is visible in a text editor,
hovering the wires and devices on the main circuit view will highlight
the corresponding lines of code in the source editor.
Simulation
The wires in the main circuit view are highlighted according to the simulation status
and one can also hover on the wires to see the signal values.
The input values for the top-level module can be changed interactively in the circuit.
The input and output ports can also be seen/controlled in the control side panel.
To start/pause the simulation, use the play/pause icon next to the editor title.
For more complex simulation control including fast-forward, single-step,
or wait for event, a more complete set of buttons is available in the control panel.
The simulation time tick is also shown in the control panel.
The magnifying glass icon on the wires allows you to monitor a signal
and create a plot for it. Clicking the icon brings up the monitor view
as part of the main circuit view. Triggering conditions can also be set up
in the monitor view.
Saving progress
The main circuit view is implemented as a custom editor and all the normal saving/restoring
operations on an editor are supported using the corresponding hotkey or menu from VS Code.
This includes saving, saving as, reverting, undo and redo.
Note that changes to the circuit layout from the graphic interface are saved
and will be part of the undo/redo history.
However, the signals in the circuit are not saved.
Note that due to VS Code limitations, saving the circuit under a different name
will close the circuit and open it under the new name, and the simulation status will be lost.
Exporting image
The circuit, including the signal levels, can be exported as either vector or raster images.
SVG, PNG and JPEG formats are supported and additional formats may also be available
depending on the host browser.
The exported image is for a single circuit view.
Images for subcircuits need to be exported individually.
Note that export of a subcircuit image requires the corresponding subcircuit to be open.
Lua scripting
For more complex control of the simulation, you can use Lua scripts.
To run a script, add it as a source file to the circuit and use the
run button in the HDL Studio files view to start it. The run button will change
into a stop button to abort the script while it is running.
In addition to the API at https://github.com/tilk/digitaljs_lua/blob/master/docs/USAGE.md,
two additional functions sim.start() and sim.stop(synchronize=false) are also supported
to start and stop the simulation.
By default, the output of the script will be shown as notification messages in VS Code.
Alternatively, you can open a Lua terminal for the circuit using the Lua Terminal button
in the HDL Studio files panel. When the terminal is visible, the output of the script
will be printed to the terminal instead. You can also use the terminal to interactively
run Lua scripts, similar to the normal Lua command-line interface. Command-line editing
and command history are supported. Pressing Ctrl-C aborts the execution of commands
from the command line (it does not stop the execution of other Lua scripts).
Starting and stopping the simulation from the Lua terminal, setting inputs and getting outputs
from the circuit:
