Design Article
USB simplified - adding USB connectivity to applications with legacy serial connections
Pedro Pachuca, Silicon Labs
1/30/2011 4:10 PM EST
Fully-compliant USB-HID bridges
To further simplify and enhance plug-and-play capabilities for designers, innovative fully-compliant USB-HID bridges are also available. Typical USB-HID to UART configurations are illustrated in figure 2. These unique bridge 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. Examples of HID-USB devices include computer keyboards and mice, but the HID-USB class is sufficiently flexible to accommodate many different kinds of USB designs.
Fig 2: HID USB-to-UART device
To keep a solution small and ergonomically efficient, 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. The CP21xx USB bridge chips overcome this constraint by using QFN space-saving packages that reduce the PCB footprint and enable the designer to squeeze a solution into a space smaller than an RS-232 connector.
These small-footprint, economical USB bridges benefit a wide range of embedded 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 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.
About the Author:
Pedro Pachuca manages Silicon Labs’ global microcontroller (MCU) interface product business. Mr. Pachuca joined Silicon Labs in early 2010. Previously, he was a product marketing manager at Freescale Semiconductor where he developed MCU business strategies to penetrate new global markets and managed a business with an annual run rate in excess of $250 million. Mr. Pachuca holds a BSSE degree from the Instituto Politecnico Nacional at Mexico City.
To further simplify and enhance plug-and-play capabilities for designers, innovative fully-compliant USB-HID bridges are also available. Typical USB-HID to UART configurations are illustrated in figure 2. These unique bridge 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. Examples of HID-USB devices include computer keyboards and mice, but the HID-USB class is sufficiently flexible to accommodate many different kinds of USB designs.
Fig 2: HID USB-to-UART device
To keep a solution small and ergonomically efficient, 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. The CP21xx USB bridge chips overcome this constraint by using QFN space-saving packages that reduce the PCB footprint and enable the designer to squeeze a solution into a space smaller than an RS-232 connector.
These small-footprint, economical USB bridges benefit a wide range of embedded 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 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.
About the Author:
Pedro Pachuca manages Silicon Labs’ global microcontroller (MCU) interface product business. Mr. Pachuca joined Silicon Labs in early 2010. Previously, he was a product marketing manager at Freescale Semiconductor where he developed MCU business strategies to penetrate new global markets and managed a business with an annual run rate in excess of $250 million. Mr. Pachuca holds a BSSE degree from the Instituto Politecnico Nacional at Mexico City.
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UnderboatBoy
2/1/2011 9:41 AM EST
A flowery introduction a little short on concrete info
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Test_engineer
2/2/2011 9:14 AM EST
Yo Underboatboy: yeah, what some people call purple prose. Connectivity, functionality, inclusity, diversity -- I hate those words! Why can't engineers write clear, concise and concrete English?
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Etmax
5/11/2011 9:10 AM EDT
Engineers do, it's the marketdroids that spin these yarns. :-)
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Test_engineer
2/2/2011 9:16 AM EST
oops! typo error; should be 'inclusivity'. It's still BS no matter how you spell it.
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sivan_ramachandran
2/3/2011 12:22 AM EST
Let us understand that this article is being written by a marketing engineer. That being the case, I think he has put his thoughts out well. At the least, I understand that I can use such a serial to USB solution in my designs without having to go through the learning curve of USB interface specification understanding (at least not a thorough understanding).
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pmoyle
2/4/2011 7:22 PM EST
I've been using the CP21xx devices for precisely the purpose mentioned for more than 4 yr now. The one glaring omission from his article is the bandwidth discussion. If you need to transfer lots of data fast you need full blown USB. My requirements for instrumentation and test interfaces are fairly minimalist and the scheme works well for that. Also on low volume/one off projects the effort required for full USB is over the top.
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t.alex
5/14/2011 4:59 AM EDT
Recently I encounter some issue with the driver for Windows 7. Is there driver for Windows 7?
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t.alex
2/10/2011 10:19 AM EST
One of the problems with USB to UART IC is they often come with unique drivers to be installed at PC side. Does this IC require any special driver?
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Etmax
5/11/2011 9:17 AM EDT
They all require a host driver of some description, in the windoze world they are called VCP or virtual comm port drivers because they make USB look like a serial port on the host side. Your micro based app sends stuff through the serial port, and your host SW uses a standard serial driver provided by the chip manufacturer. It works a treat except for really high speed apps just as pmoyle suggests. These types of devices are available from TI, SilLabs, Cypress, FTDI, Microchip and probably quite a few more that I haven't read about yet.
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Jerry.Brittingham
2/23/2011 10:04 AM EST
FTDI has been making USB interface devices for years.
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t.alex
2/26/2011 6:03 AM EST
Yep, FTDP has been common nowadays. The drivers are well supported and can be download from the website.
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