7ff0b8e876
Per the RP2040 datasheet section 4.1.2.5.1, when handing a buffer to the USB controller the AVAILABLE bit must be written after the rest of the buffer-control register (length and data PID) and after a short delay, because buffer control crosses from the system clock domain into the USB clock domain. Writing everything in a single store risks the controller acting on a stale length or PID. rp2040_update_buffer_control() wrote the whole word, AVAILABLE included, in one access. Follow the sequence the datasheet (and the Pico SDK) use: write the control word with AVAILABLE cleared, wait ~12 CPU cycles, then set AVAILABLE. The delay covers system clocks up to 12x the 48 MHz USB clock. Validated on raspberrypi-pico (RP2040) as part of bringing up cdcncm; no regression on cdcacm/usbmsc. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01AHJRvWeBMTHwzpwjaUg4HW Signed-off-by: Ricard Rosson <ricard@groundbits.com> |
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| dummy | ||
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| net | ||
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| CONTRIBUTING.md | ||
| INVIOLABLES.md | ||
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| 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.