I designed a nibble-oriented CPU in Verilog to build a scientific calculator
Summary
This project implements a fully functional scientific calculator in hardware using an FPGA, including a custom soft CPU, microcode firmware, and supporting tools. It provides a web-based simulator and open-source Verilog code.
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gdevic/FPGA-Calculator
Source: https://github.com/gdevic/FPGA-Calculator
From Gates to a Calculator
This project implements a fully functional scientific calculator in hardware using an FPGA. It includes a custom soft CPU, microcode firmware, and supporting tools.
For the full story, see the blog.
Try it in a web browser:
Project Structure
| Folder | Description |
|---|---|
verilog/ | SystemVerilog source files for the CPU, ALU, I/O, and test benches |
ucode/ | Microcode (firmware) for the soft CPU |
quartus/ | Quartus project files for FPGA synthesis |
modelsim/ | ModelSim simulation setup |
Qt/ | Qt-based simulator and debugger (uses Verilator) |
calctest/ | Command-line test harness for hardware verification (uses Verilator) |
tools/ | Assembler and script compiler for the microcode |
Pathfinding/ | Algorithm research and verification projects |
Quick Start
The fastest way to try the calculator is to build the Qt simulator:
# From WSL2
cd /mnt/c/Projects/FPGA-Calculator/verilog
make qt
Then open Qt/Calculator.pro in Qt Creator and build for “Desktop Qt MSVC2022 64 Bit”.
See the verilog/ and Qt/ folders for detailed instructions.
Required Tools
Install these tools depending on your target:
| Tool | Purpose | Notes |
|---|---|---|
| Verilator | Verilog simulation | Required for Qt simulator |
| Qt | Desktop/WebAssembly/Android app | Version 6.9+ |
| Quartus | FPGA synthesis | Version 13.0 SP1 for Cyclone II |
| ModelSim | Waveform simulation | Optional |
| Visual Studio 2022 | C++ compiler for Qt | Community Edition |
| Python 3 | Assembler and tools |
Verilator Setup
Verilator runs in WSL2 (Windows Subsystem for Linux). The project source files reside on a Windows partition and are accessed from WSL2.
| Target | Verilator Version | Notes |
|---|---|---|
| Desktop (Qt/MSVC) | 5.x (latest) | Recommended |
| WebAssembly | 4.228 | Required (no thread support) |
# Install prerequisites
sudo apt-get install build-essential autoconf flex libfl-dev bison
# Clone and build Verilator
git clone https://github.com/verilator/verilator
cd verilator
git checkout v5.042 # For Desktop, or v4.228 for WebAssembly
autoconf
./configure
make -j8
make test
# Set environment (add to .bashrc for persistence)
export VERILATOR_ROOT=$(pwd)
Optionally install GtkWave for viewing waveforms:
sudo apt install gtkwave
Build Targets
| Target | Command | Description |
|---|---|---|
| Qt Simulator | make qt in verilog/ | Build for Qt desktop application |
| Calctest | make calctest in verilog/, then make in calctest/ | Command-line test harness |
| ModelSim | make test_self in verilog/ | CPU self-test for ModelSim |
| FPGA Hardware | make revB in verilog/ | Assemble microcode for RevB board |
See the README files in each subfolder for detailed build instructions:
- verilog/README.md - Verilator simulation and microcode assembly
- calctest/README.md - Command-line test harness for hardware verification
- quartus/README.md - FPGA synthesis and programming
- ucode/README.md - Microcode source files
Pathfinding Projects
Independent research and verification projects:
| Folder | Description |
|---|---|
Pathfinding/Proto/ | BCD arithmetic golden reference for hardware verification (submodule) |
Pathfinding/Proof/ | Proofs of concept for complex operations using basic arithmetic |
Pathfinding/Methods/ | C++ implementations of calculator algorithms (deprecated) |
Pathfinding/Input/ | Numerical input state machine simulation |
Pathfinding/Mockup/ | Keyboard layout design and user interaction testing |
License
This project is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
You are free to:
- Share - copy and redistribute the material in any medium or format
- Adapt - remix, transform, and build upon the material
Under the following terms:
- Attribution - You must give appropriate credit and indicate if changes were made
- NonCommercial - You may not use the material for commercial purposes
- ShareAlike - Contributions must be distributed under the same license
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