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diff --git a/usbdrv/Readme.txt b/usbdrv/Readme.txt new file mode 100644 index 0000000..970dc66 --- /dev/null +++ b/usbdrv/Readme.txt @@ -0,0 +1,172 @@ +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/vusb/ + +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. + USB-ID-FAQ.txt ......... General infos about USB Product- and Vendor-IDs. + USB-IDs-for-free.txt ... List and terms of use for free shared PIDs. + +(*) ... 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 18 MHz and 20 MHz. Other clock rates are not supported. The +actual clock rate must be configured in usbconfig.h. + +12 MHz Clock +This is the traditional clock rate of V-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/vusb/easylogger.html for +code which calibrates the RC oscillator based on the USB frame clock. + +18 MHz Clock +This module is closer to the USB specification because it performs an on the +fly CRC check for incoming packets. Packets with invalid checksum are +discarded as required by the spec. If you also implement checks for data +PID toggling on application level (see option USB_CFG_CHECK_DATA_TOGGLING +in usbconfig.h for more info), this ensures data integrity. Due to the CRC +tables and alignment requirements, this code is bigger than modules for other +clock rates. To activate this module, you must define USB_CFG_CHECK_CRC to 1 +and USB_CFG_CLOCK_KHZ to 18000 in usbconfig.h. + +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 +USB-IDs-for-free.txt for details. + +Objective Development also has some license offerings which include product +IDs. See http://www.obdev.at/vusb/ for details. + + +DEVELOPMENT SYSTEM +================== +This driver has been developed and optimized for the GNU compiler version 3 +and 4. We recommend that you use the GNU compiler suite because it is freely +available. V-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. + +Gcc version 3 produces smaller code than version 4 due to new optimizing +capabilities which don't always improve things on 8 bit CPUs. The code size +generated by gcc 4 can be reduced with the compiler options +-fno-move-loop-invariants, -fno-tree-scev-cprop and +-fno-inline-small-functions in addition to -Os. On devices with more than +8k of flash memory, we also recommend the linker option --relax (written as +-Wl,--relax for gcc) to convert absolute calls into relative where possible. + +For more information about optimizing options see: + + http://www.tty1.net/blog/2008-04-29-avr-gcc-optimisations_en.html + +These optimizations are good for gcc 4.x. Version 3.x of gcc does not support +most of these options and produces good code anyway. + + +USING V-USB FOR FREE +==================== +The AVR firmware driver is published under the GNU General Public License +Version 2 (GPL2) and the GNU General Public License Version 3 (GPL3). It is +your choice whether you apply the terms of version 2 or version 3. + +If you decide for the free GPL2 or GPL3, we STRONGLY ENCOURAGE you to do the +following things IN ADDITION to the obligations from the GPL: + +(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/vusb/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=vusb-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/vusb/ + +(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 V-USB +============================= +If you don't want to publish your source code under the terms of the GPL, +you can simply pay money for V-USB. As an additional benefit you get +USB PIDs for free, reserved exclusively to you. See the file +"CommercialLicense.txt" for details. + |