Tensorflow lite demo running in Zephyr on Litex/VexRiscv SoC

This repository collects all the repositories required to build and run Zephyr TensorFlow Lite Micro demos on either:

• a Digilent Arty A7 board
• the open source Renode simulation framework (no hardware required)

The hardware version of the magic wand demo also requires a PmodACL to be connected to the JD port of the Arty A7 board.

Prerequisites

Clone the repository and submodules:

git clone https://github.com/antmicro/litex-vexriscv-tensorflow-lite-demo
cd litex-vexriscv-tensorflow-lite-demo
DEMO_HOME=`pwd`
git submodule update --init --recursive

Install prerequisites (tested on Ubuntu 18.04):

sudo apt update
sudo apt install cmake ninja-build gperf ccache dfu-util device-tree-compiler wget python python3-pip python3-setuptools python3-tk python3-wheel xz-utils file make gcc gcc-multilib locales tar curl unzip xxd

Install Zephyr prerequisites:

# update cmake to required version
sudo pip3 install cmake virtualenv
# install Zephyr SDK
wget https://github.com/zephyrproject-rtos/sdk-ng/releases/download/v0.11.2/zephyr-sdk-0.11.2-setup.run
chmod +x zephyr-sdk-0.11.2-setup.run
sudo ./zephyr-sdk-0.11.2-setup.run -- -d /opt/zephyr-sdk

Export Zephyr configuration:

export ZEPHYR_TOOLCHAIN_VARIANT=zephyr
export ZEPHYR_SDK_INSTALL_DIR=/opt/zephyr-sdk

Building the demos

Hello World demo

Build the Hello World demo with:

cd $DEMO_HOME/tensorflow
make -f tensorflow/lite/micro/tools/make/Makefile TARGET=zephyr_vexriscv hello_world_bin

The resulting binaries can be found in the tensorflow/lite/micro/tools/make/gen/zephyr_vexriscv_x86_64/hello_world/build/zephyr folder.

Magic Wand demo

Build the Magic Wand demo with:

cd $DEMO_HOME/tensorflow
make -f tensorflow/lite/micro/tools/make/Makefile TARGET=zephyr_vexriscv magic_wand_bin

The resulting binaries can be found in the tensorflow/lite/micro/tools/make/gen/zephyr_vexriscv_x86_64/magic_wand/build/zephyr folder.

Building the gateware

Note: For this section, if you have not already updated your udev rules, follow the instructions at "Download & setup udev rules" -- you probably won't need to reboot.

The FPGA bitstream (gateware) can be built using Litex Build Environment. Building the gateware currently requires Xilinx's FPGA tooling, Vivado, to be installed in the system.

Build the gateware with:

cd $DEMO_HOME/litex-buildenv

# Some of LiteX Buildenv's scritps have problems when running in a git repository in detached state.
# Let's create a fake branch to avoid build errors.
git checkout -b tf_demo

export CPU=vexriscv
export CPU_VARIANT=full
export PLATFORM=arty
export FIRMWARE=zephyr
export TARGET=tf

./scripts/download-env.sh
source scripts/enter-env.sh

make gateware

Once you have synthesized the gateware, load it onto the FPGA with:

make gateware-load

With the FPGA programmed, you can load the Zephyr binary on the device using the flterm program provided inside the environment you just initialized above:

cd $DEMO_HOME/tensorflow
flterm --port=/dev/ttyUSB1 --kernel=tensorflow/lite/micro/tools/make/gen/zephyr_vexriscv_x86_64/magic_wand/build/zephyr/zephyr.bin --speed=115200

See the Litex Build Environment Wiki for more available options.

Simulating in Renode

The renode directory contains all necessary scripts and assets required to simulate the Magic Wand demo.

Install Renode as detailed in its README file.

Build the Magic Wand demo as described in the section above or use a prebuilt binary from the binares/magic_wand directory.

Now you should have everything to run the simulation using the locally built binary:

cd $DEMO_HOME/renode
renode -e "s @litex-vexriscv-tflite.resc"

Or using the prebuilt one:

cd $DEMO_HOME/renode
renode -e "set zephyr_elf @../binaries/magic_wand/zephyr.elf; s @litex-vexriscv-tflite.resc"

You should see the following output on the UART (which will open as a separate terminal in Renode automatically):

*** Booting Zephyr OS build 0.6.0-86741-g626bb2c4d0bd  ***
4 bytes lost due to alignment. To avoid this loss, please make sure the tensor_arena is 16 bytes aligned.
Got accelerometer, label: accel-0

RING:
          *
       *     *
     *         *
    *           *
     *         *
       *     *
          *

SLOPE:
        *
       *
      *
     *
    *
   *
  *
 * * * * * * * *

RING:
          *
       *     *
     *         *
    *           *
     *         *
       *     *
          *

SLOPE:
        *
       *
      *
     *
    *
   *
  *
 * * * * * * * * 

In order to exit Renode, type quit in Monitor (the window with the Renode logo and (machine-0) prompt).

Refer to the Renode documentation for details on how to use Renode to implement more complex usage scenarios, and use its advanced debug capabilities, or set up CI testing your ML-oriented system. If you need commercial support, please contact us at [email protected].