Progress is being made to deploy convolutional neural networks (CNNs) into the Internet of Things (IoT) edge devices for handling image analysis tasks locally. These tasks require low-latency and low-power computation on low-resource IoT edge devices. However, CNN-based algorithms, e.g. YOLOv2, typically contain millions of parameters. With the increase in the CNN’s depth, filters are increased by a power of two. A large number of filters and operations could lead to frequent off-chip memory access that affects the operation speed and power consumption of the device. Therefore, it is a challenge to map a deep CNN into a low-resource edge IoT platform. To address this challenge, we present a resource-constrained Field-Programmable Gate Array implementation of YOLOv2 with optimized data transfer and computing efficiency. Firstly, a scalable cross-layer dataflow strategy is proposed which allows on-chip data transfer between different types of layers, and offers flexible off-chip data transfer when the intermediate results are unaffordable on-chip. Next, a filter-level data-reuse dataflow strategy together with a filter-level parallel multiply-accumulate operation computing processing elements array is developed. Finally, multi-level sliding buffers are developed to optimize the convolutional computing loop and reuse the input feature maps and weights. Experiment results show that our implementation has achieved 4.8 W of low-power consumption for executing YOLOv2, an 8-bit deep CNN containing 50.6 MB weights, using low-resource of 8.3 Mbits on-chip memory. The throughput and power efficiency are 100.33 GOP/s and 20.90 GOP/s/W, respectively.