173 lines
8.3 KiB
Plaintext
173 lines
8.3 KiB
Plaintext
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.
|
|
|