A USB 3.0 High Speed Digital Readout System with Dynamic Frame Rate Processing for ISFET Lab-on-Chip Platforms

Abstract

This paper presents a USB 3.0 based readout platform for real-time ion imaging applications. The front end utilizes an ion-imaging array containing 16 k ISFET pixels to capture ion diffusion at 6100 fps. Operating at 200 MHz, the chip streams ion information at a data rate of 762.94 Mb/s. The backend readout system employs a FIFO-to-USB bridge (FT601Q) that supports Super Speed (5 Gbps) to perform real-time data streaming and operates in bulk transfer mode to ensure data integrity. Implemented on a Xilinx Virtex UltraScale+ FPGA, the system involves a high-throughput data path through the on-board DDR4 SDRAMs, based on which a ring buffer is designed to provide the 2 GB buffering capacity. The readout system can operate in real time regardless of the USB glitches encountered on the Windows OS when involving data polling. In addition, a simple differencing algorithm with threshold detection is integrated into the back end for dynamic frame rate operation. The proposed readout system performs real-time ion imaging at high speed as well as streams the collected images for visualization within a latency of 25 ms, achieving state-of-the-art performance for high-speed Lab-on-Chip applications.