Prep for 6.5 release

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@3730 42af7a65-404d-4744-a932-0658087f49c3

ReleaseNotes

@@ -1901,4 +1901,83 @@ This release also includes some completed but untest functionality.
       testing.  Unfortunately, testing will be delayed due to tool issues.
     * Support for the NXP LPC315x MCUs.
 
-Additional miscellaneous enhancements and bug fixes to task_delete(), recvfrom(), and other changes as noted in the ChangeLog.
+Additional miscellaneous enhancements and bug fixes to task_delete(), recvfrom(),
+and other changes as noted in the ChangeLog.
+
+nuttx-6.5
+^^^^^^^^^
+
+The 72nd release of NuttX, Version 6.5, was made on June 21, 2011 and is
+available for download from the SourceForge website.  The 6.5 release
+is all about support for the Atmel 8-bit AVR family.  I have been
+interested in the AVR family for some time but because of the severe
+SRAM constraints and because of the availability of many tiny schedulers
+for the AVR, it has not been "on the radar screen."  However, I have
+recently become interested because of interest expressed by members of
+the forum and because of the availability of newer, larger capacity AVR
+parts (that I don't have yet).
+
+This release includes support for the following AVR boards.  As with any
+initial support for new architectures, there are some incomplete areas
+and a few caveats that need to be stated.  Here they are, ordered from
+the least to the most complete:
+
+    * SoC Robotics Amber Web Server (ATMega128).
+
+      This port of NuttX to the Amber Web Server from SoC Robotics
+      (http://www.soc-robotics.com/index.htm).  Is only partially in place.
+      The Amber Web Server is based on an Atmel ATMega128 (128Kb FLASH
+      but only 4Kb of SRAM).
+
+      STATUS: Work on this port has stalled due to toolchain issues.  It
+      is complete, but untested.
+
+    * Micropendous 3 AT9USB647
+
+      This port of NuttX to the Opendous Micropendous 3 board. The
+      Micropendous3 may be populated with an AT90USB646, 647, 1286, or
+      1287.  See http://code.google.com/p/opendous/. I have only the
+      AT90USB647 version for testing.  This version has very limited
+      memory resources: 64Kb of FLASH and 4Kb of SRAM.
+
+      STATUS: The basic port was released in NuttX-6.5.  This basic port
+      consists only of a "Hello, World!!" example that demonstrates
+      initialization of the OS, creation of a simple task, and serial
+      console output.  The tiny SRAM limits what you can do with the
+      AT90USB647 (see issues below).
+
+    * PJRC Teensy++ 2.0 AT9USB1286
+
+      This is a port of NuttX to the PJRC Teensy++ 2.0 board.  This board
+      was developed by PJRC (http://pjrc.com/teensy/). The Teensy++ 2.0 is
+      based on an Atmel AT90USB1286 MCU with 128Kb of FLASH and 8Kb of SRAM;
+      a little more room to move than the AT90USB647.
+
+      STATUS:  The basic port was released in NuttX-6.5.  This basic port
+      consists of a "Hello, World!!" example and also slightly simplified
+      NuttShell (NSH) configuration (see the NSH User Guide at
+      http://www.nuttx.org/NuttShell.html).
+
+      An SPI driver and a USB device driver exist for the AT90USB as well
+      as a USB mass storage configuration.  However, this configuration is not
+      fully debugged as of the NuttX-6.5 release.
+
+AVR-specific issues.  The basic AVR port is solid and biggest issue for using
+AVR is its tiny SRAM memory and its Harvard architecture.  Because of the
+Harvard architecture, constant data that resides to flash is inaccessible using
+"normal" memory reads and writes (only SRAM data can be accessed "normally").
+Special AVR instructions are available for accessing data in FLASH, but these
+have not been integrated into the normal, general purpose OS.
+
+Most NuttX test applications are console-oriented with lots of strings used
+for printf and debug output.  These strings are all stored in SRAM now due to
+these data accessing issues and even the smallest console-oriented applications
+can quickly fill a 4-8Kb memory.  So, in order for the AVR port to be useful,
+one of two things would need to be done:
+
+1. Don't use console applications that required lots of strings.  The basic
+   AVR port is solid and your typical deeply embedded application should work
+   fine.
+
+2. Create a special version of printf that knows how to access strings that
+   reside in FLASH (or EEPROM).