USB Simplified Adding USB Connectivity to Applications with Legacy Serial Connections

USB has become an enormous success in industrial and commercial applications as it continues to replace many legacy serial connections (i.e. RS-232, 485). It is becoming the interface of choice for enabling connectivity to new applications with its ease of use, plug-and-play functionality and increased robustness.

USB has achieved its primary goal of simplifying the way consumers control peripherals and transfer data. With more than three billion USB-enabled devices shipped into the market, USB is not only the fastest growing interface in consumer applications but has also achieved significant growth in industrial markets.

Finally, another factor that needs to be considered when implementing USB is that of increased hardware design cost due to the USB-based microcontroller requiring external components, such as crystal oscillators and termination resistors, to provide the USB functionality. This is typically the case with many USB-based microcontrollers.

"Wouldn’t it be a major step forward in USB evolution if all the benefits that end users enjoy (ease of use, plug and play functionality and robustness) were also available to designers?"

Pursuing a simplified and economical USB implementation for designers should be the cornerstone for new USB IC solutions. This approach requires a highly-integrated solution that simplifies hardware design and reduces cost by eliminating external components.

Solutions that can provide all of the above benefits and can be implemented in the system using standard interfaces, such as RS-232, RS-485 or I²C, are available on the market today. These solutions represent a major step forward in supporting the continued penetration of USB in the marketplace.


The CP21xx USB bridge family is a highly-integrated solution that enables USB connectivity to be added to virtually any microcontroller-based solution. These devices provide a bridge to the USB world through the use of the standard UART or I²C interface common on most microcontrollers.

In addition, CP21xx products use a novel clock recovery system that reduces costs by eliminating the need for an external crystal oscillator. Further cost savings are achieved through the integration of a full USB transceiver designed to eliminate the need for external termination resistors.

USB bridges offering GPIO control capability, clock output functions and a voltage regulator that can be used to power external components are also available. These features can further reduce cost by eliminating additional external components.

Another attractive feature of the USB to UART bridges is the flexibility to support multiple Baud rates to fit a wide range of applications. These USB bridges are supported by a software ecosystem that ranges from royalty-free drivers to API libraries, thereby providing complete solutions.

To further simplify and enhance plug-and-play capabilities for designers, innovative fully-compliant USB-HID bridges are also available. These unique devices fully support the USB-HID class that is natively supported by most operating systems, thereby eliminating the need for driver installation.

In order to keep a solution small and ergonomic, portable applications require that PCB space be minimized. In addition, some legacy applications may require keeping the same physical dimensions while upgrading their application to include USB connectivity.

These high-value, low-cost USB bridges greatly benefit a large number of applications, such as portable medical and industrial connectivity applications, that require easy yet robust implementations of USB to be able to communicate with modern systems or computers.

In conclusion, USB bridges are an easy and economical approach to adding USB connectivity to microcontroller-based solutions. Their high integration reduces cost, and their simplicity eliminates the need for USB firmware development, which, in turn, enables designers to focus their time and resources on innovating and differentiating their applications.

To know more about HID USB and Easy USB check out Silicon Labs website
www.silabs.com