84 lines
3.6 KiB
Groff
84 lines
3.6 KiB
Groff
|
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 corresponds with SVN release number: r3730
|
||
|
|
|
||
|
|
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
|
||
|
|
(128K FLASH but only 4K 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: 64K of FLASH and 4K 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 128K
|
||
|
|
of FLASH and 8K 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 https://nuttx.apache.org/docs/latest/components/nsh/index.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 4-8K
|
||
|
|
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).
|