This file documents changes in the firmware-only USB driver for atmel's AVR
microcontrollers. New entries are always appended to the end of the file.
Scroll down to the bottom to see the most recent changes.

2005-04-01:
  - Implemented endpoint 1 as interrupt-in endpoint.
  - Moved all configuration options to usbconfig.h which is not part of the
    driver.
  - Changed interface for usbVendorSetup().
  - Fixed compatibility with ATMega8 device.
  - Various minor optimizations.

2005-04-11:
  - Changed interface to application: Use usbFunctionSetup(), usbFunctionRead()
    and usbFunctionWrite() now. Added configuration options to choose which
    of these functions to compile in.
  - Assembler module delivers receive data non-inverted now.
  - Made register and bit names compatible with more AVR devices.

2005-05-03:
  - Allow address of usbRxBuf on any memory page as long as the buffer does
    not cross 256 byte page boundaries.
  - Better device compatibility: works with Mega88 now.
  - Code optimization in debugging module.
  - Documentation updates.

2006-01-02:
  - Added (free) default Vendor- and Product-IDs bought from voti.nl.
  - Added USBID-License.txt file which defines the rules for using the free
    shared VID/PID pair.
  - Added Readme.txt to the usbdrv directory which clarifies administrative
    issues.

2006-01-25:
  - Added "configured state" to become more standards compliant.
  - Added "HALT" state for interrupt endpoint.
  - Driver passes the "USB Command Verifier" test from usb.org now.
  - Made "serial number" a configuration option.
  - Minor optimizations, we now recommend compiler option "-Os" for best
    results.
  - Added a version number to usbdrv.h

2006-02-03:
  - New configuration variable USB_BUFFER_SECTION for the memory section where
    the USB rx buffer will go. This defaults to ".bss" if not defined. Since
    this buffer MUST NOT cross 256 byte pages (not even touch a page at the
    end), the user may want to pass a linker option similar to
    "-Wl,--section-start=.mybuffer=0x800060".
  - Provide structure for usbRequest_t.
  - New defines for USB constants.
  - Prepared for HID implementations.
  - Increased data size limit for interrupt transfers to 8 bytes.
  - New macro usbInterruptIsReady() to query interrupt buffer state.

2006-02-18:
  - Ensure that the data token which is sent as an ack to an OUT transfer is
    always zero sized. This fixes a bug where the host reports an error after
    sending an out transfer to the device, although all data arrived at the
    device.
  - Updated docs in usbdrv.h to reflect changed API in usbFunctionWrite().

* Release 2006-02-20

  - Give a compiler warning when compiling with debugging turned on.
  - Added Oleg Semyonov's changes for IAR-cc compatibility.
  - Added new (optional) functions usbDeviceConnect() and usbDeviceDisconnect()
    (also thanks to Oleg!).
  - Rearranged tests in usbPoll() to save a couple of instructions in the most
    likely case that no actions are pending.
  - We need a delay between the SET ADDRESS request until the new address
    becomes active. This delay was handled in usbPoll() until now. Since the
    spec says that the delay must not exceed 2ms, previous versions required
    aggressive polling during the enumeration phase. We have now moved the
    handling of the delay into the interrupt routine.
  - We must not reply with NAK to a SETUP transaction. We can only achieve this
    by making sure that the rx buffer is empty when SETUP tokens are expected.
    We therefore don't pass zero sized data packets from the status phase of
    a transfer to usbPoll(). This change MAY cause troubles if you rely on
    receiving a less than 8 bytes long packet in usbFunctionWrite() to
    identify the end of a transfer. usbFunctionWrite() will NEVER be called
    with a zero length.

* Release 2006-03-14

  - Improved IAR C support: tiny memory model, more devices
  - Added template usbconfig.h file under the name usbconfig-prototype.h

* Release 2006-03-26

  - Added provision for one more interrupt-in endpoint (endpoint 3).
  - Added provision for one interrupt-out endpoint (endpoint 1).
  - Added flowcontrol macros for USB.
  - Added provision for custom configuration descriptor.
  - Allow ANY two port bits for D+ and D-.
  - Merged (optional) receive endpoint number into global usbRxToken variable.
  - Use USB_CFG_IOPORTNAME instead of USB_CFG_IOPORT. We now construct the
    variable name from the single port letter instead of computing the address
    of related ports from the output-port address.

* Release 2006-06-26

  - Updated documentation in usbdrv.h and usbconfig-prototype.h to reflect the
    new features.
  - Removed "#warning" directives because IAR does not understand them. Use
    unused static variables instead to generate a warning.
  - Do not include <avr/io.h> when compiling with IAR.
  - Introduced USB_CFG_DESCR_PROPS_* in usbconfig.h to configure how each
    USB descriptor should be handled. It is now possible to provide descriptor
    data in Flash, RAM or dynamically at runtime.
  - STALL is now a status in usbTxLen* instead of a message. We can now conform
    to the spec and leave the stall status pending until it is cleared.
  - Made usbTxPacketCnt1 and usbTxPacketCnt3 public. This allows the
    application code to reset data toggling on interrupt pipes.

* Release 2006-07-18

  - Added an #if !defined __ASSEMBLER__ to the warning in usbdrv.h. This fixes
    an assembler error.
  - usbDeviceDisconnect() takes pull-up resistor to high impedance now.

* Release 2007-02-01

  - Merged in some code size improvements from usbtiny (thanks to Dick
    Streefland for these optimizations!)
  - Special alignment requirement for usbRxBuf not required any more. Thanks
    again to Dick Streefland for this hint!
  - Reverted to "#warning" instead of unused static variables -- new versions
    of IAR CC should handle this directive.
  - Changed Open Source license to GNU GPL v2 in order to make linking against
    other free libraries easier. We no longer require publication of the
    circuit diagrams, but we STRONGLY encourage it. If you improve the driver
    itself, PLEASE grant us a royalty free license to your changes for our
    commercial license.

* Release 2007-03-29

  - New configuration option "USB_PUBLIC" in usbconfig.h.
  - Set USB version number to 1.10 instead of 1.01.
  - Code used USB_CFG_DESCR_PROPS_STRING_DEVICE and
    USB_CFG_DESCR_PROPS_STRING_PRODUCT inconsistently. Changed all occurrences
    to USB_CFG_DESCR_PROPS_STRING_PRODUCT.
  - New assembler module for 16.5 MHz RC oscillator clock with PLL in receiver
    code.
  - New assembler module for 16 MHz crystal.
  - usbdrvasm.S contains common code only, clock-specific parts have been moved
    to usbdrvasm12.S, usbdrvasm16.S and usbdrvasm165.S respectively.

* Release 2007-06-25
