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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 your own version of "usbconfig.h". A template for your own "usbconfig.h" can be found in "usbconfig-prototype.h" in this directory. 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! usbdrvasm12.S .......... 12 MHz version of the assembler routines. Included by usbdrvasm.S, don't link it directly! usbdrvasm16.S .......... 16 MHz version of the assembler routines. Included by usbdrvasm.S, don't link it directly! usbdrvasm165.S ......... 16.5 MHz version of the assembler routines including a PLL so that an 1% accurate RC oscillator can be used. Included by usbdrvasm.S, don't link 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, 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. 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. We recommend that you obtain appropriate calibration values for 16.5 MHz core clock at programming time and store it in flash or EEPROM or compute the value from a reference clock at run time. However, since Atmel's 8 MHz calibration is much more precise than the guaranteed 10%, it's usually possible to add a fixed offset to this value. 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 a single VID/PID pair for free. If you want to use your own VID and PID instead of our's, define the macros "USB_CFG_VENDOR_ID" and "USB_CFG_DEVICE_ID" accordingly in "usbconfig.h". To use our predefined VID/PID pair, you MUST conform to a couple of requirements. See the file "USBID-License.txt" for details. Objective Development also has some offerings which include product IDs. See http://www.obdev.at/avrusb/ for details. HOST DRIVER =========== You have received this driver together with an example device implementation and an example host driver. The host driver is based on libusb and compiles on various Unix flavors (Linux, BSD, Mac OS X). It also compiles natively on Windows using MinGW (see www.mingw.org) and libusb-win32 (see libusb-win32.sourceforge.net). The "Automator" project contains a native Windows host driver (not based on libusb) for Human Interface Devices. DEVELOPMENT SYSTEM ================== This driver has been developed and optimized for the GNU compiler version 3 (gcc 3). It does work well with gcc 4 and future versions will probably be optimized for gcc 4. 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. 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. (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.