Silicon Labs CP21xx USB bridge family: 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. For embedded solution designers, implementing USB requires expert knowledge of the USB protocol, software development and significant design time. Additionally, USB-based MCUs may not offer the right peripheral set required for an application. This results in time-to-market delays, increased design complexity and added cost. There is, however, a painless and economical approach to adding USB connectivity to any embedded MCU-based solution. It requires no USB expertise or firmware development.
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. It also requires the elimination of USB software development to enable USB ease-of-use and maximize design time. Finally, to eliminate the need for driver installation, solutions should come with fully-tested, royalty-free drivers that are compatible with most operating systems and capable of supporting the USB-defined classes natively supported by most operating systems.
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. CP21xx USB bridges from Silicon Laboratories are excellent examples of such solutions. The benefits provided by these USB bridges and the ways that design complexity can be eliminated and implementation costs reduced.
- Silicon Labs CP21xx USB Bridge Smart Interface Family (click to enlarge)
The CP21xx USB bridge family is a highly-integrated solution that enables USB connectivity to be added to virtually any MCU-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 order to simplify the design and reduce cost, the CP21xx family integrates the hardware and software necessary to interface with USB and serial interfaces.
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. For customization purposes, in-system programming memory enables full customization of many USB parameters, such as Vendor ID, Product ID, product descriptions, etc.
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. The USB-HID class predefines functions that allow hardware manufacturers to design a product to USB-HID class specifications and expect it to work with any software that also meets these specifications. USB-HID class drivers are included in most modern operating systems allowing faster deployment of devices and easier installation by end users.
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. By means of a simple connection to a standard serial interface, such as an RS-232, RS-485 or I²C , USB bridges enable designers to add USB connectivity to these applications without the painful efforts involved in redesigning an entire system.
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. USB-HID based solutions further simplify the implementation of USB by eliminating the need to install drivers, thereby providing seamless compatibility with most operating systems. In combination, this makes USB easy not only for consumers but for designers as well.