Fri 29 March 2019

Codethink creates custom USB 3 switch to support customer's CI/CD pipeline requirements

by Tim Pockney , 2019 , Tags CI CD USB USB3 continuous integration PCB KiCAD

Over the course of three months and two PCB revisions, Codethink developed a USB 3 switch (See Image) in order to address issues regarding software deployment and continuous integration faced by one of our major customers.

The aim was to deliver a computer-controlled, automated deployment pipeline for testing software on actual target hardware, without reliance on human interaction for flashing or power-cycling of target hardware.

The board, designed by Codethink, features two SuperSpeed USB 3 host ports and a single USB 3 device port, alongside another USB 2 host control port for programmatically controlling which of the two USB 3 host is connected to the device. The control port is also capable of selecting which host powers the device, and configuring numerous banks of GPIO for other automation.

Design for USB 3 requires more attention to detail than USB 2, due to the higher speed digital signals involved with USB 3.

The main challenge faced in development of the USB 3 switch is making sure that care is given for all USB 3 transmission lines to avoid as much noise as possible. In order to meet these challenges, Codethink used FOSS KiCAD software. This was used for schematic capture and PCB layout. The tools available for differential routing and track length matching were used in order to make sure that transmission lines were treated carefully and detail was maintained. Research was also conducted into transmission line theory to further understand techniques that are involved in mitigating complications arising from such high speed digital systems.

USB 3 Switch