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Rebuilding finn-examples

Although this repo comes with pre-synthesized bitfiles, it's possible to re-generate those. This can be useful for customizing the existing examples, or for building to target new Xilinx FPGA platforms. Rebuilding uses the FINN compiler and must happen on a host x86 PC with Vivado/Vitis installed.

Setup

  1. Run the get-finn.sh under this directory to clone FINN at the appropriate commit. Note that you may have to do this again in the future when the finn-examples repo gets updated and requires FINN at a newer commit.

  2. Ensure you have the requirements for FINN installed, which includes Docker community edition docker-ce.

  3. Set up the environment variables to point to your Vivado/Vitis installation, depending on your target platform(s):

    • For Zynq platforms you'll need to set VIVADO_PATH, e.g. VIVADO_PATH=/opt/xilinx/Vivado/2019.1/
    • For Alveo platforms you'll need to set VITIS_PATH, PLATFORM_REPO_PATHS and XILINX_XRT

Build bitfiles

Please see the READMEs under the respective subfolders here for instructions on how to rebuild the bitfiles.

How do I use my custom bitfile? What about the software/drivers?

All examples in this repo use the same Python PYNQ driver, located under finn_examples/driver.py in the repo. This driver can support any FINN-generated accelerator, the only thing that needs to be specified is the configuration for the input and output tensors in the io_shape_dict. Have a look at finn_examples/models.py to see how this is done for the example models in this repo:

_cifar10_cnv_io_shape_dict = {
    # FINN DataType for input and output tensors
    "idt" : DataType.UINT8,
    "odt" : DataType.UINT8,
    # shapes for input and output tensors (NHWC layout)
    "ishape_normal" : (1, 32, 32, 3),
    "oshape_normal" : (1, 1),
    # folded / packed shapes below depend on idt/odt and input/output
    # PE/SIMD parallelization settings -- these are calculated by the
    # FINN compiler, you can see them in the generated Python driver
    "ishape_folded" : (1, 1, 32, 32, 1, 3),
    "oshape_folded" : (1, 1, 1),
    "ishape_packed" : (1, 1, 32, 32, 1, 3),
    "oshape_packed" : (1, 1, 1),
}

Instead of using the driver.py provided in the repo, you can also use the generated driver under the output folder.

Building Vivado IP instead of bitfiles

It's possible to build the examples here as Vivado IP to target any Xilinx FPGA of sufficient size, and integrate the generated IP into any Vivado IPI design using AXI Stream interfaces. To do this, you'll need to launch the build for the example(s) you are interested in as described above, but with the DataflowOutputType.STITCHED_IP as part of the DataflowBuildConfig.generate_outputs list in the build script, and customize the DataflowBuildConfig.fpga_part to reflect the desired Xilinx FPGA part number. You can also remove the DataflowOutputType.BITFILE from the outputs list to to avoid building the bitfile itself. The generated IP can be found in the outputs folder, under the stitched_ip subfolder.