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f6ecf80ebb
The documentation grew one page at a time, so the tree follows the
history of who wrote what and not the shape of NuttX. Scheduling is
spread over three places, a driver page can sit above the subsystem
that owns it, and the front page lists everything at the same level.
That is a lot to face when all you want to know is where the scheduler
lives.
This change files every page under the code it describes. It is a move,
not a rewrite: outside the ten pages named below, every page keeps the
text that is already in master, and no page's text is deleted.
What it does:
* Groups the table of contents into nine chapters.
* Moves the OS subsystems under os/: scheduling, memory, drivers,
filesystem, networking, IPC, interrupts, libs, time.
* Renames the platform pages to the names the source tree uses, and
derives their tags from the tree instead of by hand.
* Splits guides/ by subject.
* Adds Documentation/redirects.py, with a rule for every page that left
its old path, so old URLs keep working. The redirect page also carries
a link's #anchor across to the new page.
Ten pages have text that is new or rewritten. Nine of them are the
landing page of a chapter, which has to exist for the new structure:
index the front page
os/index OS Design
os/scheduling/index Scheduling
os/interrupts/index Interrupts
os/ipc/index IPC
os/time/index Time and timers
about/index About
developing/index Developing NuttX
ReleaseNotes/index Release notes
The tenth is os/libs/libbuiltin, the only page here with technical
content: libs/libbuiltin/ had no page at all. Five SVG diagrams come
with these pages, hand-written XML with no editor metadata.
Nothing outside Documentation/ is touched.
How it was checked:
* Sphinx builds with -W: no warnings, and no document left outside a
toctree.
* A script, offered in the PR, proves the narrow claim this rests on.
For every page outside the ten named above it erases what a move
touches -- link target, path, tag line, toctree block, table border --
from the whole old text and the whole new text, and requires the two
to be byte for byte identical. It also requires every sentence of a
deleted page to turn up somewhere, and every page that left its old
path to have a redirect, from a URL that existed, to where its content
went. It exits non-zero and names the page if any of that is not true,
and it tests added pages too, so forgetting to declare one cannot make
it pass.
* An independent audit checked 133 factual claims on these ten pages
against the tree, one shell command per claim: 130 confirmed, 1
refuted and fixed here, 2 not checkable.
* tools/checkpatch.sh is clean over the range.
The diff is large because moving a page changes every link that points
to it. Most of it is pure renames, and board pages that gained one tag
line.
Assisted-by: Claude:claude-opus-5
83 lines
3.6 KiB
Markdown
83 lines
3.6 KiB
Markdown
NuttX-6.5
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=========
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The 72nd release of NuttX, Version 6.5, was made on June 21, 2011
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and is available for download from the SourceForge website. The
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6.5 release is all about support for the Atmel 8-bit AVR family.
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I have been interested in the AVR family for some time but because
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of the severe SRAM constraints and because of the availability of
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many tiny schedulers for the AVR, it has not been "on the radar
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screen." However, I have recently become interested because of
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interest expressed by members of the forum and because of the
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availability of newer, larger capacity AVR parts (that I don't have
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yet).
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This release corresponds with SVN release number: r3730
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This release includes support for the following AVR boards. As
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with any initial support for new architectures, there are some
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incomplete areas and a few caveats that need to be stated. Here
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they are, ordered from the least to the most complete:
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* SoC Robotics Amber Web Server (ATMega128).
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This port of NuttX to the Amber Web Server from SoC Robotics
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(http://www.soc-robotics.com/index.htm). Is only partially in
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place. The Amber Web Server is based on an Atmel ATMega128
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(128K FLASH but only 4K of SRAM).
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STATUS: Work on this port has stalled due to toolchain issues. It
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is complete, but untested.
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* Micropendous 3 AT9USB647
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This port of NuttX to the Opendous Micropendous 3 board. The
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Micropendous3 may be populated with an AT90USB646, 647, 1286,
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or 1287. See http://code.google.com/p/opendous/. I have only
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the AT90USB647 version for testing. This version has very
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limited memory resources: 64K of FLASH and 4K of SRAM.
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STATUS: The basic port was released in NuttX-6.5. This basic
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port consists only of a "Hello, World!!" example that demonstrates
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initialization of the OS, creation of a simple task, and serial
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console output. The tiny SRAM limits what you can do with the
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AT90USB647 (see issues below).
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* PJRC Teensy++ 2.0 AT9USB1286
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This is a port of NuttX to the PJRC Teensy++ 2.0 board. This
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board was developed by PJRC (http://pjrc.com/teensy/). The
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Teensy++ 2.0 is based on an Atmel AT90USB1286 MCU with 128K
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of FLASH and 8K of SRAM; a little more room to move than the
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AT90USB647.
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STATUS: The basic port was released in NuttX-6.5. This basic
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port consists of a "Hello, World!!" example and also slightly
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simplified NuttShell (NSH) configuration (see the NSH User Guide
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at https://nuttx.apache.org/docs/latest/components/nsh/index.html).
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An SPI driver and a USB device driver exist for the AT90USB as
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well as a USB mass storage configuration. However, this
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configuration is not fully debugged as of the NuttX-6.5 release.
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AVR-specific issues. The basic AVR port is solid and biggest issue
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for using AVR is its tiny SRAM memory and its Harvard architecture.
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Because of the Harvard architecture, constant data that resides to
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flash is inaccessible using "normal" memory reads and writes (only
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SRAM data can be accessed "normally"). Special AVR instructions
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are available for accessing data in FLASH, but these have not been
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integrated into the normal, general purpose OS.
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Most NuttX test applications are console-oriented with lots of
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strings used for printf and debug output. These strings are all
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stored in SRAM now due to these data accessing issues and even the
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smallest console-oriented applications can quickly fill a 4-8K
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memory. So, in order for the AVR port to be useful, one of two
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things would need to be done:
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1. Don't use console applications that required lots of strings.
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The basic AVR port is solid and your typical deeply embedded
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application should work fine.
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2. Create a special version of printf that knows how to access
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strings that reside in FLASH (or EEPROM).
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