V-USB is a software-only implementation of a low-speed USB device for Atmel’s AVR® microcontrollers, making it possible to build USB hardware with almost any AVR® microcontroller, not requiring any additional chip.

V-USB can be licensed freely under the GNU General Public License or alternatively under a commercial license.

A comprehensive set of example projects demonstrates the wide range of possible applications.

Features

Fully USB 1.1 compliant low-speed device, except handling of communication errors and electrical specifications. Example projects demonstrate device and host driver implementations on Linux, Mac OS X and Windows. Supports multiple endpoints: one control endpoint, two interrupt/bulk-in endpoints and up to 7 interrupt/bulk-out endpoints. (Bulk endpoints are forbidden for low speed devices by the USB standard.) Transfer sizes up to 254 bytes by default, more as configuration option. Comes with freely usable USB identifiers (Vendor-ID and Product-ID pairs).

Runs on any AVR microcontroller with at least 2 kB of Flash memory, 128 bytes RAM and a clock rate of at least 12 MHz. No UART, timer, input capture unit or other special hardware is required (except one edge triggered interrupt). Can be clocked with 12 MHz, 15 MHz, 16 MHz or 20 MHz crystal or from a 12.8 MHz or 16.5 MHz internal RC oscillator. High level functionality is written in C and is well commented. Only about 1150 to 1400 bytes code size. You can choose the License: Open Source or commercial. Click here for details.

For a comparison to other USB solutions for microcontrollers please click here.

Hardware

This diagram shows a typical circuit for a bus powered device (click the image to enlarge).

D1 and D2 are a low cost replacement for a low drop 3.3 V regulator chip, such as the LE33. Operating the AVR at higher voltages exceeds the common mode range of many USB chips. If you need to run the AVR at 5 V, add 3.6 V zener diodes at D+ and D- to limit the voltage.

For a prototyping board, please see metaboard.

Documentation Resources

• Download the V-USB package containing a short description and several simple code examples.
• V-USB Wiki is a public Wiki with lots of additional information.
• There is also an excellent step by step tutorial by Code and Life.

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V-USB

Information

• Overview
• Benefits
• Licensing
• Download
• Reference Projects
• Links

Community Resources

• Community Projects
• Documentation Wiki
• Forum
• Feedback

Related Information

• Article: Implementing USB 1.1 in Firmware
• CrossPack for AVR Development

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