AVR ISP MEGA8

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. usbportability.h ....... Header with compiler-dependent stuff. 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, 12.8 MHz, 15 MHz, 16 MHz, 16.5 MHz and 20 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. 12.8 MHz and 16.5 MHz Clock The assembler modules for these clock rates differ from the other modules because they have 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 reach 16.5 MHz with the RC oscillator. This includes the very popular ATTiny25, ATTiny45, ATTiny85 series as well as the ATTiny26. Almost all AVRs can reach 12.8 MHz, although this is outside the specified range. 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. 20 MHz Clock This module is for people who won't do it with less than the maximum. Since 20 MHz is not divisible by the USB low speed bit clock of 1.5 MHz, the code uses similar tricks as the 16 MHz module to insert leap cycles. 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 at http://www.obdev.at/goto.php?t=avrusb-wiki&p=hosted-projects. (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.