# SymbiFlow examples

This repository provides example FPGA designs that can be built using SymbiFlow open source toolchain.
The examples target the Artix-7 devices.

The repository includes:

* Travis CI configuration file
* Build scripts to generate the environment:
  * Conda configurations
  * Python requirements
  * Environment setup

* Example FPGA designs including:

  * Verilog code
  * Pin constraints files
  * Timing constraints files
  * Makefiles for running the SymbiFlow toolchain

## Description

Travis-based CI in this repository runs all the steps required to build the example designs and generate bitstreams for programming the FPGA devices.

The CI performs the following steps:

* [Miniconda](https://docs.conda.io/en/latest/miniconda.html) installation and configuration
* Installation of the required conda packages (toolchains and Python modules). Note that Python packages can be installed using any Python package manager:

    * [VTR](https://anaconda.org/symbiflow/vtr)
    * [Yosys](https://anaconda.org/symbiflow/yosys)
    * [Yosys-plugins](https://anaconda.org/symbiflow/yosys-plugins)
    * [lxml](https://anaconda.org/conda-forge/lxml), [simplejson](https://anaconda.org/conda-forge/simplejson), [intervaltree](https://anaconda.org/conda-forge/intervaltree), [python-constraint](https://anaconda.org/conda-forge/python-constraint), [git](https://anaconda.org/conda-forge/git), [pip](https://anaconda.org/conda-forge/pip) and [fasm](https://github.com/SymbiFlow/fasm)

## Toolchain installation

This block of code regards the toolchain installation. It is divided in three main steps:

- Conda setup
- Conda packages installation
- Architecture definitions installation

```bash
INSTALL_DIR=/opt/symbiflow
wget https://repo.continuum.io/miniconda/Miniconda3-latest-Linux-x86_64.sh
bash Miniconda3-latest-Linux-x86_64.sh -b -p $INSTALL_DIR/conda && rm Miniconda3-latest-Linux-x86_64.sh
source $INSTALL_DIR/conda/etc/profile.d/conda.sh
conda update -y -q conda
wget -qO- https://storage.googleapis.com/symbiflow-arch-defs/artifacts/prod/foss-fpga-tools/symbiflow-arch-defs/continuous/install/4/20200416-002215/symbiflow-arch-defs-install-a321d9d9.tar.xz | tar -xJ -C $INSTALL_DIR
conda install -y -c symbiflow yosys yosys-plugins
conda install -y -c symbiflow -c conda-forge vtr=8.0.0.rc2_3575_g253f75b6d
conda install -y make lxml simplejson intervaltree git pip
conda activate
pip install python-constraint
pip install git+https://github.com/symbiflow/fasm
conda deactivate
```

## Build Example Designs

With the toolchain installed, you can build the example designs.

The example designs are provided in separate directories:

1. `counter` - simple 4-bit counter driving LEDs. The design targets the [Basys3 board](https://store.digilentinc.com/basys-3-artix-7-fpga-trainer-board-recommended-for-introductory-users/) .
1. `picosoc` - [picorv32](https://github.com/cliffordwolf/picorv32) based SoC. The design targets the [Basys3 board](https://store.digilentinc.com/basys-3-artix-7-fpga-trainer-board-recommended-for-introductory-users/).
1. `linux_litex` - [LiteX](https://github.com/enjoy-digital/litex) based system with Linux capable [VexRiscv core](https://github.com/SpinalHDL/VexRiscv). The design includes [DDR](https://github.com/enjoy-digital/litedram) and [Ethernet](https://github.com/enjoy-digital/liteeth) controllers. The design targets the [Arty board](https://store.digilentinc.com/arty-a7-artix-7-fpga-development-board-for-makers-and-hobbyists/).

The Linux images for the `linux_litex` example can be build following the [linux on litex vexriscv](https://github.com/litex-hub/linux-on-litex-vexriscv) instructions.
The `linux_litex` example is already provided with working Linux images.

To build the examples, run following commands:

```bash
export INSTALL_DIR=/opt/symbiflow
# adding symbiflow toolchain binaries to PATH
export PATH=$INSTALL_DIR/install/bin:$PATH
source $INSTALL_DIR/conda/etc/profile.d/conda.sh
conda activate
git clone https://github.com/SymbiFlow/symbiflow-examples && cd symbiflow-examples
# counter example
pushd counter_test && make && popd
# picosoc example
pushd picosoc_demo && make && popd
# litex example
pushd linux_litex_demo && make && popd
```