Whitepaper
Simplifying Universal Serial Bus Connectivity with USB Bridge Devices
The universal serial bus (USB) interface is one of the most successful communication standards in the electronics industry. It has become the standard communication interface for many industrial and consumer applications that require connectivity to a host device. USB’s extreme ease of use coupled with robustness makes it the ideal choice of interface for many embedded applications.
Introduction
The universal serial bus (USB) interface is one of the most successful communication standards in the electronics industry. It has become the standard communication interface for many industrial and consumer applications that require connectivity to a host device. USB’s extreme ease of use coupled with robustness makes it the ideal choice of interface for many embedded applications.
However, for embedded designers, a USB implementation requires USB protocol expertise, time-consuming software and firmware development effort. Most often, designers of these embedded applications are required to provide an end solution that is highly cost effective. The simplest way to achieve this is by integrating the USB functionality in the microcontroller (MCU) along with other peripherals and memory.
Many MCU vendors today offer USB-based microcontrollers. However, they may not offer the right peripheral set required for an application, resulting in the need for external components and increased design complexity. There’s also a no-hassle approach for adding USB to any embedded solution, with no need for USB expertise or firmware development, enabling faster times to market for designers.
USB Design Challenges
The ease of use and robustness of USB do not come for free for embedded designers. Developers often have to spend significant time learning the USB protocol and developing a USB stack. This requires specialized tools and can increase development costs and time. There are commercially available USB software stacks. However, they result in additional costs and learning effort. Another important USB design challenge is the fact that the final product must be compatible with several common operating systems (OS) and keep up with constant OS updates. Developers also must keep the USB hardware costs to a minimum to provide a cost-effective final product. Many USB ICs require external components, such as termination resistors or precision oscillators to provide USB functionality. Highly integrated USB solutions with advanced software and tools support are the cornerstone to simplifying USB design.
The Practical Fix: Turnkey USB Connectivity Solutions
The ease of use and robustness of USB do not come for free for embedded designers. Developers often have to spend significant time learning the USB protocol and developing a USB stack.
Choosing the Right USB Bridge for Your Application
Eliminate external crystal, regulator and memory with highly integrated USB bridges
Additionally, USB bridges offering GPIO control capability and clock output functions add flexibility to designs and shorten development times. Another attractive feature to consider in bridge devices is the flexibility to support multiple baud rates to fit a wide range of applications.
Some modern USB bridge devices also offer advanced features to further conserve the PCB area. For example, the CP2102N device from Silicon Labs includes an integrated battery charger detection feature that detects the type of charger connected and a remote wake-up feature to wake up a suspended host. Inclusion of such advanced features on-chip not only enhances flexibility for embedded designs but also saves overall system cost.
Finally, designers must minimize USB space to meet the form factor and ergonomic requirements of space-sensitive portable applications. In addition, some legacy applications may require keeping the same physical dimensions while upgrading the application to include USB connectivity. Choosing USB bridges that offer small package variants helps overcome this constraint by reducing the PCB footprint and enabling the designer to squeeze a solution into a space smaller than an RS-232 connector.
Example of a 3 mm x 3 mm USB bridge IC and complete solution in a small PCB
Accelerated USB Development with Advanced Tools
Example of an advanced tool GUI for USB bridge configuration
Software Drivers
Virtual COM Port USB bridge recognized as a COM port in the device manager