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+This is the Readme file to Objective Development's firmware-only USB driver
+for Atmel AVR microcontrollers. For more information please visit
+http://www.obdev.at/avrusb/
+
+This directory contains the USB firmware only. Copy it as-is to your own
+project and add all .c and .S files to your project (these files are marked
+with an asterisk in the list below). Then copy usbconfig-prototype.h as
+usbconfig.h to your project and edit it according to your configuration.
+
+
+TECHNICAL DOCUMENTATION
+=======================
+The technical documentation (API) for the firmware driver is contained in the
+file "usbdrv.h". Please read all of it carefully! Configuration options are
+documented in "usbconfig-prototype.h".
+
+The driver consists of the following files:
+  Readme.txt ............. The file you are currently reading.
+  Changelog.txt .......... Release notes for all versions of the driver.
+  usbdrv.h ............... Driver interface definitions and technical docs.
+* usbdrv.c ............... High level language part of the driver. Link this
+                           module to your code!
+* usbdrvasm.S ............ Assembler part of the driver. This module is mostly
+                           a stub and includes one of the usbdrvasm*.S files
+                           depending on processor clock. Link this module to
+                           your code!
+  usbdrvasm*.inc ......... Assembler routines for particular clock frequencies.
+                           Included by usbdrvasm.S, don't link it directly!
+  asmcommon.inc .......... Common assembler routines. Included by
+                           usbdrvasm*.inc, don't link it directly!
+  usbconfig-prototype.h .. Prototype for your own usbdrv.h file.
+* oddebug.c .............. Debug functions. Only used when DEBUG_LEVEL is
+                           defined to a value greater than 0. Link this module
+                           to your code!
+  oddebug.h .............. Interface definitions of the debug module.
+  iarcompat.h ............ Compatibility definitions for IAR C-compiler.
+  usbdrvasm.asm .......... Compatibility stub for IAR-C-compiler. Use this
+                           module instead of usbdrvasm.S when you assembler
+                           with IAR's tools.
+  License.txt ............ Open Source license for this driver.
+  CommercialLicense.txt .. Optional commercial license for this driver.
+  USBID-License.txt ...... Terms and conditions for using particular USB ID
+                           values for particular purposes.
+
+(*) ... These files should be linked to your project.
+
+
+CPU CORE CLOCK FREQUENCY
+========================
+We supply assembler modules for clock frequencies of 12 MHz, 15 MHz, 16 MHz and
+16.5 MHz. Other clock rates are not supported. The actual clock rate must be
+configured in usbdrv.h unless you use the default 12 MHz.
+
+12 MHz Clock
+This is the traditional clock rate of AVR-USB because it's the lowest clock
+rate where the timing constraints of the USB spec can be met.
+
+15 MHz Clock
+Similar to 12 MHz, but some NOPs inserted. On the other hand, the higher clock
+rate allows for some loops which make the resulting code size somewhat smaller
+than the 12 MHz version.
+
+16 MHz Clock
+This clock rate has been added for users of the Arduino board and other
+ready-made boards which come with a fixed 16 MHz crystal. It's also an option
+if you need the slightly higher clock rate for performance reasons. Since
+16 MHz is not divisible by the USB low speed bit clock of 1.5 MHz, the code
+is somewhat tricky and has to insert a leap cycle every third byte.
+
+16.5 MHz Clock
+The assembler module for this clock rate differs from the other modules because
+it has been built for an RC oscillator with only 1% precision. The receiver
+code inserts leap cycles to compensate for clock deviations. 1% is also the
+precision which can be achieved by calibrating the internal RC oscillator of
+the AVR. Please note that only AVRs with internal 64 MHz PLL oscillator can be
+used since the 8 MHz RC oscillator cannot be trimmed up to 16.5 MHz. This
+includes the very popular ATTiny25, ATTiny45, ATTiny85 series as well as the
+ATTiny26.
+
+See the EasyLogger example at http://www.obdev.at/avrusb/easylogger.html for
+code which calibrates the RC oscillator based on the USB frame clock.
+
+
+USB IDENTIFIERS
+===============
+Every USB device needs a vendor- and a product-identifier (VID and PID). VIDs
+are obtained from usb.org for a price of 1,500 USD. Once you have a VID, you
+can assign PIDs at will.
+
+Since an entry level cost of 1,500 USD is too high for most small companies
+and hobbyists, we provide some VID/PID pairs for free. See the file
+USBID-License.txt for details.
+
+Objective Development also has some license offerings which include product
+IDs. See http://www.obdev.at/avrusb/ for details.
+
+
+DEVELOPMENT SYSTEM
+==================
+This driver has been developed and optimized for the GNU compiler version 3
+(gcc 3). It does work well with gcc 4, but with bigger code size. We recommend
+that you use the GNU compiler suite because it is freely available. AVR-USB
+has also been ported to the IAR compiler and assembler. It has been tested
+with IAR 4.10B/W32 and 4.12A/W32 on an ATmega8 with the "small" and "tiny"
+memory model. Not every release is tested with IAR CC and the driver may
+therefore fail to compile with IAR. Please note that gcc is more efficient for
+usbdrv.c because this module has been deliberately optimized for gcc.
+
+
+USING AVR-USB FOR FREE
+======================
+The AVR firmware driver is published under the GNU General Public License
+Version 2 (GPL2). See the file "License.txt" for details.
+
+If you decide for the free GPL2, we STRONGLY ENCOURAGE you to do the following
+things IN ADDITION to the obligations from the GPL2:
+
+(1) Publish your entire project on a web site and drop us a note with the URL.
+Use the form at http://www.obdev.at/avrusb/feedback.html for your submission.
+If you don't have a web site, you can publish the project in obdev's
+documentation wiki.
+
+(2) Adhere to minimum publication standards. Please include AT LEAST:
+    - a circuit diagram in PDF, PNG or GIF format
+    - full source code for the host software
+    - a Readme.txt file in ASCII format which describes the purpose of the
+      project and what can be found in which directories and which files
+    - a reference to http://www.obdev.at/avrusb/
+
+(3) If you improve the driver firmware itself, please give us a free license
+to your modifications for our commercial license offerings.
+
+
+COMMERCIAL LICENSES FOR AVR-USB
+===============================
+If you don't want to publish your source code under the terms of the GPL2,
+you can simply pay money for AVR-USB. As an additional benefit you get
+USB PIDs for free, licensed exclusively to you. See the file
+"CommercialLicense.txt" for details.
+