  Edge computing devices inherently face tight resource constraints, which is
especially apparent when deploying Deep Neural Networks (DNN) with high memory
and compute demands. FPGAs are commonly available in edge devices. Since these
reconfigurable circuits can achieve higher throughput and lower power
consumption than general purpose processors, they are especially well-suited
for DNN acceleration. However, existing solutions for designing FPGA-based DNN
accelerators for edge devices come with high development overheads, given the
cost of repeated FPGA synthesis passes, reimplementation in a Hardware
Description Language (HDL) of the simulated design, and accelerator system
integration.
  In this paper we propose SECDA, a new hardware/software co-design methodology
to reduce design time of optimized DNN inference accelerators on edge devices
with FPGAs. SECDA combines cost-effective SystemC simulation with hardware
execution, streamlining design space exploration and the development process
via reduced design evaluation time. As a case study, we use SECDA to
efficiently develop two different DNN accelerator designs on a PYNQ-Z1 board, a
platform that includes an edge FPGA. We quickly and iteratively explore the
system's hardware/software stack, while identifying and mitigating performance
bottlenecks. We evaluate the two accelerator designs with four common DNN
models, achieving an average performance speedup across models of up to
3.5$\times$ with a 2.9$\times$ reduction in energy consumption over CPU-only
inference. Our code is available at https://github.com/gicLAB/SECDA
