AVR-USB

AVR-USB implements a USB device entirely in software, making it possible to build USB hardware with almost any AVR microcontroller, not requiring any additional chip.

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

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

• 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 16.5 MHz internal RC oscillator.
• High level functionality is written in C and is well commented.
• Only about 1200 to 1400 bytes code size.
• You can choose the License: Open Source or commercial. Click here for details.