a6b45dd471
RGBTO8 shifted each component up before masking:
(((uint8_t)(r) << 5) & 0xe0)
The cast is promoted to int before the shift, so the mask keeps bits 5:7
of the shifted value, which are bits 0:2 of r. The macro therefore
encoded the three least significant bits of red and green and the two
least significant bits of blue, rather than the most significant.
This disagrees with RGBTO16 in the same file, which correctly takes the
high bits, and with RGB8RED/RGB8GREEN/RGB8BLUE immediately below it,
which are documented as the inverse transformation but read the result
as high bits.
All in-tree callers pass full 8-bit components, so all were affected:
RGBTO8(39, 64, 139) in apps/examples/nxterm, intended as midnight blue,
evaluates to 0xe3 -- full red plus full blue, i.e. magenta.
Take the high bits instead, so that RGBTO8 matches RGBTO16 and the
RGB8xxx macros become its true inverse.
Tested on a RISC-V LiteX/VexRiscv target with an 8bpp RGB332 frame
buffer, and with a host round-trip check over all 256 representable
colours.
Assisted-by: Claude:claude-opus-5
Signed-off-by: William Byatt <william@byatt.io>
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| .github | ||
| arch | ||
| audio | ||
| binfmt | ||
| boards | ||
| cmake | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| dummy | ||
| fs | ||
| graphics | ||
| include | ||
| libs | ||
| mm | ||
| net | ||
| openamp | ||
| pass1 | ||
| sched | ||
| syscall | ||
| tools | ||
| video | ||
| wireless | ||
| .asf.yaml | ||
| .codespell-ignore-lines | ||
| .codespellrc | ||
| .editorconfig | ||
| .gitignore | ||
| .gitmessage | ||
| .pre-commit-config.yaml | ||
| .yamllint | ||
| AUTHORS | ||
| CMakeLists.txt | ||
| CONTRIBUTING.md | ||
| INVIOLABLES.md | ||
| Kconfig | ||
| LICENSE | ||
| Makefile | ||
| NOTICE | ||
| README.md | ||
| ReleaseNotes | ||
Apache NuttX is a real-time operating system (RTOS) with an emphasis on standards compliance and small footprint. Scalable from 8-bit to 64-bit microcontroller environments, the primary governing standards in NuttX are POSIX and ANSI standards. Additional standard APIs from Unix and other common RTOSs (such as VxWorks) are adopted for functionality not available under these standards, or for functionality that is not appropriate for deeply-embedded environments (such as fork()).
For brevity, many parts of the documentation will refer to Apache NuttX as simply NuttX.
Getting Started
First time on NuttX? Read the Getting Started guide! If you don't have a board available, NuttX has its own simulator that you can run on terminal.
Documentation
You can find the current NuttX documentation on the Documentation Page.
Alternatively, you can build the documentation yourself by following the Documentation Build Instructions.
The old NuttX documentation is still available in the Apache wiki.
Supported Boards
NuttX supports a wide variety of platforms. See the full list on the Supported Platforms page.
Contributing
If you wish to contribute to the NuttX project, read the Contributing guidelines for information on Git usage, coding standard, workflow and the NuttX principles.
License
The code in this repository is under either the Apache 2 license, or a license compatible with the Apache 2 license. See the License Page for more information.