Introduction

This project implements a ORB feature extractor accelerator on FPGA (on PYNQ-Z2 board). ORB ( Oriented FAST and Rotated BRIEF) feature is a kind of image feature based on oriented FAST feature and BRIEF descriptor. It's easy to calculate and robust to rotating so it's widely used in embedded computer vision application. For example, it's used in feature matching of some SLAM (Simultaneous Localization And Mapping) system, such as ORB-SLAM and ORB-SLAM2. SLAM system help robot or other platform to locate themselves and build a map of their surroudings. Here is a brief explanation of how ORB Features are extracted.

The extractor will take a gray image and applys a FAST extractor on it. After feature points being found, it will calculate m01 and m10 moment of the feature points and figure out the angles of them. Calculating BRIEF descriptors needs those angles and a gray image which is the original gray image applied a 7x7 gaussian filter.

Result

1.Resource Utilizaton (on Pynq-Z2)

Resource	Utilization	Available	Utilization
LUT	35807	53200	67.31
LUTRAM	1412	17400	8.11
FF	54895	106400	51.59
BRAM18K	50	140	35.71
DSP	24	220	10.91

2.Performance (testing on images in 640*480)

Platform	Average Delay	Throughoutput
PS 650mHz -O	291.7 ms	3.43 FPS
PS 650mHz -O2	98.5 ms	10.20 FPS
PL 140mHz	17.56 ms	56.58 FPS

3. Result Picture

Feature points are drawn on the picture.Descriptors can be read in the buffer filled by DMA.

Quick Start

Run these command lines on your Pynq-Z2 Board (tested on v2.4):

sudo pip3 install git+https://github.com/Siudya/ORB_FPGA.git

Contents of each folder

ip

HLS sources files

pynq_arch

Vivado project

pynq_notebook

Notebook run in Jupyter Notebook

software_test

A .cpp file that test the same process on CPU

test_data

Images for testing

hw

.bit and .hwh files for PYNQ

How to rebuild Vivado project

vivado 2018.3 is required.

Step 1: rebuild HLS IP

Open Vivado HLS command terminal and run these commands :

cd <path-to-proj>/ip
vivado_hls -f build_ip.tcl

This should take about half an hour.

Step 2: rebuild top project

Open Vivado command terminal and run these commands :

cd <path-to-proj>/pynq_arch
source pynq_arch.tcl