Thank you Swatantra and KeroGit, I gave my approval on the github :-)
Would these devkits work for runtime testing?
1. AVR128DA48 CURIOSITY NANO EVALUATION KIT
https://www.microchip.com/en-us/development-tool/DM164151
2. AVR128DB48 CURIOSITY NANO EVALUATION KIT
https://www.microchip.com/en-us/development-tool/EV35L43A
--
CeDeROM, SQ7MHZ, http://www.tomek.cedro.info
On Thu, Oct 29, 2026 at 3:46 PM Swatantra
<[email protected]> wrote:
>
> Hello Kerogit,
> I have rebased the AVR DA/DB software interrupt emulation patch series
> (`avrdx_swint`) onto latest master and submitted the Pull Request on your
> behalf:
> https://github.com/apache/nuttx/pull/21129
>
> All commit authorship, DCO sign-offs, and checkpatch requirements have been
> verified.
>
> Best regards,
> Swatantra
>
> On Wed, 28 Oct 2026 at 05:11, <[email protected]> wrote:
>
> > Hello,
> >
> > I noticed that the previous phase got merged - thanks to everyone
> > involved. Step 3 is support for software interrupt emulation, branch
> > name is avrdx_swint. Documentation builds without conflicts and
> > checkpatch reports all checks pass for every changed source code file.
> >
> > ============================
> >
> > AVR: software interrupt emulation
> >
> > ## Summary
> >
> > This patch adds emulated software interrupt functionality to AVR DA/DB
> > architecture. The chip itself does not have any software interrupt and
> > the suggested way to implement one is to manipulate an I/O pin
> > configured to trigger a hardware interrupt. The implementation can serve
> > multiple users at the same time and also supports sharing the hardware
> > interrupt of the I/O port with other users.
> >
> > There is no in-tree user of this functionality yet, intended use is a
> > follow-up patch series that adds driver for WS2812 programmable LED.
> >
> > ## Impact
> >
> > **New feature**: software interrupt emulation for AVR DA/DB family
> >
> > **Impact on user**: none, new code is not enabled by default. Other AVR
> > families are not supported and not affected.
> >
> > **Impact on build**: new Kconfig options related to the new feature,
> > none otherwise
> >
> > **Impact on documentation**: zero latency interrupts guide updated
> > (mentions software interrupt emulation as a way to "get back into the
> > game")
> >
> > No impact on hardware, security or compatibility
> >
> > ## Testing
> >
> > I confirm that changes are verified on local setup and works as
> > intended:
> > * Build Host(s): Linux, AMD, GCC avr-gcc 14.2
> > * Target(s): AVR DA/DB, tested on breadxavr
> >
> > Tested with the (not yet merged) WS2812 driver which uses this
> > functionality to notify the OS that the data transmission performed by
> > the zero latency interrupt handler is finished.
> >
> > Other than that - Documentation tested by make html, changed source code
> > files tested with checkpatch.sh
> >
> > ## PR verification Self-Check
> >
> > * [x] This PR introduces only one functional change.
> > * [x] I have updated all required description fields above.
> > * [x] My PR adheres to Contributing
> > [Guidelines](https://github.com/apache/nuttx/blob/master/CONTRIBUTING.md)
> > and
> > [Documentation](
> > https://nuttx.apache.org/docs/latest/contributing/index.html)
> > (git commit title and message, coding standard, etc).
> > * [ ] My PR is still work in progress (not ready for review).
> > * [x] My PR is ready for review and can be safely merged into a
> > codebase.
> >
> > ============================
> >
> >
> > On 2026-10-16 18:20, Swatantra wrote:
> > > Hi, No worries at all. Aspell definitely generates a lot of false
> > > positives
> > > with embedded hardware terminology, and Sphinx's autosectionlabel
> > > extension
> > > is notorious for flagging duplicate headings across sections.
> > >
> > > That's the beauty of pair-shepherding—catching those CI quirks together
> > > makes the upstream submission smooth.
> > >
> > > The force-pushed commit is now building cleanly in GitHub Actions CI. I
> > > will keep an eye on the review progress with Alin and the maintainers
> > > and
> > > keep you posted here.
> > >
> > > Best regards,
> > > Swatantra Yadav
> > >
> > > On Fri, 16 Oct 2026 at 21:39, <[email protected]> wrote:
> > >
> > >> Hi, thanks for posting the patches and for the fixes. I am
> > >> spellchecking
> > >> the commits as well but there is lot of noise (aspell doesn't like the
> > >> word datasheet, let alone AVR) so it's unfortunately easy to miss
> > >> something. And sorry about the duplicate label, I tested that document
> > >> with make html and found and fixed 2 of those warnings but it did not
> > >> occur to me that this label needs to be fixed in earlier patch than
> > >> where I did it.
> > >>
> > >> On 2026-10-16 17:00, Swatantra wrote:
> > >> > Hi Kerogit,
> > >> >
> > >> > I have submitted your Phase 2 series (Zero Latency Interrupt Handlers)
> > >> > as a
> > >> > pull request on GitHub:
> > >> >
> > >> > PR: https://github.com/apache/nuttx/pull/20706
> > >> >
> > >> > Details of the submission:
> > >> > - Rebased cleanly on top of the latest apache/nuttx master (which
> > >> > includes
> > >> > merged PR #20677).
> > >> > - Fixed a minor documentation typo ("overriden" -> "overridden") in
> > >> > zerolatencyinterrupts.rst so that GitHub Actions CI checks (codespell)
> > >> > pass
> > >> > cleanly.
> > >> > - Preserved your original author attribution and DCO sign-off
> > >> > exclusively
> > >> > across all 4 commits.
> > >> > - Validated with checkpatch.sh and cvt2utf (0 errors, 0 warnings).
> > >> >
> > >> >
> > >> > Best regards,
> > >> > Swatantra Yadav
> > >> >
> > >> > On Fri, 16 Oct 2026 at 18:08, <[email protected]> wrote:
> > >> >
> > >> >> Hello, thanks, I see it merged, next step is zero latency interrupt
> > >> >> handling in branch named avrdx_zerolatency_intr. It rebased cleanly
> > on
> > >> >> current master branch. PR description is:
> > >> >>
> > >> >> ============================
> > >> >>
> > >> >> AVR: support for zero latency interrupt handlers
> > >> >>
> > >> >> ## Summary
> > >> >>
> > >> >> This patch series provides support for so-called zero latency
> > >> >> interrupts
> > >> >> as described in
> > >> >>
> > >> >>
> > >>
> >
https://nuttx.apache.org/docs/latest/guides/concurrency/zerolatencyinterrupts.html
> > >> >> . These can be used for driver code that needs the interrupt handler
> > >> >> to
> > >> >> run with as little overhead as possible (for example because it is
> > >> >> latency sensitive, runs very often etc.) This series does not add any
> > >> >> in-tree user, that is a topic of a planned follow-up (driver for
> > >> >> WS2812
> > >> >> programmable LED.)
> > >> >>
> > >> >> This support is only added for DA/DB family of AVR chips.
> > >> >>
> > >> >> There are also some fixes of interrupt vectors table (incorrectly
> > >> >> numbered vectors as a result of duplicates) and Kconfig option
> > naming.
> > >> >> In addition to that, interupt vectors are renamed (for DA/DB family
> > >> >> only) to be able to override them with custom code written in C (and
> > >> >> compiled with GCC which expects __vector prefix in the name.)
> > >> >>
> > >> >> ## Impact
> > >> >>
> > >> >> New feature is added: zero latency interrupts that override regular
> > >> >> interrupt routine with a custom code completely independent on the
> > >> >> rest
> > >> >> of the operating system.
> > >> >>
> > >> >> There is no impact on existing users, all new code is off by default.
> > >> >> No
> > >> >> impact on other architectures nor other AVR families either.
> > >> >>
> > >> >> Impact on build - some Kconfig options are renamed from HAS_ to
> > >> >> preferred HAVE_ form. This renaming only touches existing Kconfig
> > >> >> options that are referred to by newly added Kconfig options (ie. the
> > >> >> new
> > >> >> option depends on the existing one.) All of the renamed options are
> > >> >> selected automatically based on chip in use so this change should
> > have
> > >> >> no impact on existing configurations.
> > >> >>
> > >> >> Impact on documentation - the guide linked in the summary is updated
> > >> >> to
> > >> >> describe specifics of the AVR implementation.
> > >> >>
> > >> >> No impact on hardware, security or compatibility.
> > >> >>
> > >> >> ## Testing
> > >> >>
> > >> >> I confirm that changes are verified on local setup and works as
> > >> >> intended:
> > >> >> * Build Host: Linux, AMD, GCC - avr-gcc 14.2
> > >> >> * Target: AVR DA/DB, tested on breadxavr board
> > >> >>
> > >> >> To test that the interrupt vector renaming did not affect other AVR
> > >> >> families, mega1284p-xplained:nsh was built and disassembly compared.
> > >> >> There was no change.
> > >> >>
> > >> >> The feature was first tested by rudimentary application that
> > >> >> controlled
> > >> >> WS2812 programmable LED outside of the OS and then by a new driver
> > for
> > >> >> that LED using ws2812 example application from nuttx-apps.
> > >> >>
> > >> >> ## PR verification Self-Check
> > >> >>
> > >> >> * [x] This PR introduces only one functional change.
> > >> >> * [x] I have updated all required description fields above.
> > >> >> * [x] My PR adheres to Contributing
> > >> >> [Guidelines](
> > >> https://github.com/apache/nuttx/blob/master/CONTRIBUTING.md)
> > >> >> and
> > >> >> [Documentation](
> > >> >> https://nuttx.apache.org/docs/latest/contributing/index.html)
> > >> >> (git commit title and message, coding standard, etc).
> > >> >> * [ ] My PR is still work in progress (not ready for review).
> > >> >> * [x] My PR is ready for review and can be safely merged into a
> > >> >> codebase.
> > >> >>
> > >> >> ============================
> > >> >>
> > >> >> On 2026-10-15 07:41, Swatantra wrote:
> > >> >> > Hi Kerogit, Alin,
> > >> >> >
> > >> >> > I have opened the Pull Request for Step 1 on GitHub on behalf of
> > >> >> > Kerogit:
> > >> >> > https://github.com/apache/nuttx/pull/20677
> > >> >> >
> > >> >> > All 4 commits preserve Kerogit's original authorship and DCO
> > >> sign-offs,
> > >> >> > rebased cleanly onto current master, and checked with nxstyle.
> > >> >> > As discussed, we will proceed step-by-step: once this PR is
> > reviewed
> > >> >> > and
> > >> >> > merged, we can proceed with Step 2 (Zero Latency Interrupts).
> > >> >> >
> > >> >> > Best regards,
> > >> >> > Swatantra Yadav
> > >> >> >
> > >> >> > On Thu, 15 Oct 2026 at 03:15, <[email protected]> wrote:
> > >> >> >
> > >> >> >> Hello,
> > >> >> >>
> > >> >> >> thanks to everyone for the offers. First part of the series is
> > ready
> > >> >> >> in
> > >> >> >> the Git repository, branch is named avrdx_fixes_13.1. The PR
> > >> >> >> description
> > >> >> >> is below. I'll be looking at Github and if any question arise, I
> > will
> > >> >> >> answer them here.
> > >> >> >>
> > >> >> >> And just in case - since you mention splitting the patches into
> > >> >> >> individual PRs. If you mean breaking the branch into 4 separate
> > >> >> >> branches, I would advise against that. The features more or less
> > >> >> >> depend
> > >> >> >> on each other (software interrupt emulation changes file added by
> > the
> > >> >> >> zero latency interrupts, WS2812 uses both of these features etc.)
> > so
> > >> >> >> trying to split them up is most likely going to end with git
> > >> conflicts
> > >> >> >> and code that does not build. That's why I was planning to merge
> > this
> > >> >> >> in
> > >> >> >> step-by-step fashion.
> > >> >> >>
> > >> >> >> The filled PR template:
> > >> >> >>
> > >> >> >> ============================
> > >> >> >>
> > >> >> >> AVR DA/DB: fix for build failure and other smaller fixes
> > >> >> >>
> > >> >> >> ## Summary
> > >> >> >>
> > >> >> >> This patch series fixes build failure for AVR DA/DB family and
> > adds
> > >> >> >> some
> > >> >> >> other smaller fixes.
> > >> >> >>
> > >> >> >> The build failure was caused by patch series that added
> > >> >> >> LIBC_ATOMIC_IRQ
> > >> >> >> Kconfig option during 13.1 development. Commit 4ca2256a9bee
> > selects
> > >> >> >> this
> > >> >> >> option by default for AVR chips but not for the DA/DB family,
> > causing
> > >> >> >> a
> > >> >> >> build failure (atomic functions are missing.) The first patch of
> > this
> > >> >> >> series simply adds missing "select LIBC_ATOMIC_IRQ" for this
> > family
> > >> as
> > >> >> >> well.
> > >> >> >>
> > >> >> >> Other than that, version 13.1 added a performance regression which
> > >> >> >> manifested as dropped bytes in USART peripheral during receive
> > (with
> > >> >> >> heavy round-robin preemptive scheduling load.) The regression was
> > >> >> >> bisected to commit b32712d0a2 that fixes some bugs (which were
> > >> >> >> affecting
> > >> >> >> AVR DA/DB default build as well) but apparently adds more
> > >> >> >> time-consuming
> > >> >> >> work to context switch with interrupts disabled. The patch for
> > this
> > >> >> >> simply documents this possibility in the USART driver description.
> > >> >> >>
> > >> >> >> The remaining patches fix unused variable warning, make (very
> > >> >> >> unlikely)
> > >> >> >> board initialization error more visible and reorder manipulation
> > with
> > >> >> >> stack pointer during context restore to do it in the way
> > (presumably)
> > >> >> >> intended by the chip manufacturer.
> > >> >> >>
> > >> >> >> ## Impact
> > >> >> >>
> > >> >> >> After the patch is applied, it is again possible to build the
> > code.
> > >> >> >> Other than that, there is no impact on existing code/users.
> > >> >> >>
> > >> >> >> The stack pointer reordering change is done in file shared with
> > other
> > >> >> >> AVR families - #ifdef blocks are used to cause no change for them
> > >> >> >>
> > >> >> >> ## Testing
> > >> >> >>
> > >> >> >> I confirm that changes are verified on local setup and work as
> > >> >> >> intended:
> > >> >> >> * Build Host: Linux, AMD, GCC-AVR 14.2
> > >> >> >> * Target: AVR (AVR128DA28), breadxavr:nsh
> > >> >> >>
> > >> >> >> Testing logs before change:
> > >> >> >>
> > >> >> >> ```
> > >> >> >> $ tools/configure.sh -l breadxavr:nsh
> > >> >> >> $ make -j16
> > >> >> >> ...
> > >> >> >> avr-ld: .../nuttx.git/staging/libsched.a(sem_destroy.o): in
> > function
> > >> >> >> `.L3':
> > >> >> >> sem_destroy.c:(.text.nxsem_destroy+0x46): undefined reference to
> > >> >> >> `__atomic_load_4'
> > >> >> >> ...
> > >> >> >> ```
> > >> >> >>
> > >> >> >> Testing logs after change:
> > >> >> >>
> > >> >> >> ```
> > >> >> >> $ tools/configure.sh -l breadxavr:nsh
> > >> >> >> $ make -j16
> > >> >> >> Register: nsh
> > >> >> >> Register: sh
> > >> >> >> LD: nuttx
> > >> >> >> Memory region Used Size Region Size %age Used
> > >> >> >> flash: 56377 B 128 KB 43.01%
> > >> >> >> sram: 780 B 16 KB 4.76%
> > >> >> >> eeprom: 0 B 512 B 0.00%
> > >> >> >> rodata: 606 B 4 KB 14.79%
> > >> >> >> CP: nuttx.hex
> > >> >> >> CP: nuttx.asm
> > >> >> >> ```
> > >> >> >>
> > >> >> >> To verify that the stack pointer change did not affect other AVR
> > >> >> >> families, mega1284p-xplained:nsh was built before and after the
> > >> >> >> change.
> > >> >> >> The resulting binary was identical (with the exception of version
> > >> >> >> string.)
> > >> >> >>
> > >> >> >> Header and source files were checked by checkpatch with no issues
> > >> >> >> found,
> > >> >> >> spelling checked with aspell.
> > >> >> >>
> > >> >> >> ## PR verification Self-Check
> > >> >> >>
> > >> >> >> * [x] This PR introduces only one functional change.
> > >> >> >> * [x] I have updated all required description fields above.
> > >> >> >> * [x] My PR adheres to Contributing
> > >> >> >> [Guidelines](
> > >> >> https://github.com/apache/nuttx/blob/master/CONTRIBUTING.md)
> > >> >> >> and
> > >> >> >> [Documentation](
> > >> >> >> https://nuttx.apache.org/docs/latest/contributing/index.html)
> > >> >> >> (git commit title and message, coding standard, etc).
> > >> >> >> * [ ] My PR is still work in progress (not ready for review).
> > >> >> >> * [x] My PR is ready for review and can be safely merged into a
> > >> >> >> codebase.
> > >> >> >>
> > >> >> >> ============================
> > >> >> >>
> > >> >> >> On 2026-10-14 18:20, Abhishek Mishra wrote:
> > >> >> >> > Hi,
> > >> >> >> >
> > >> >> >> > I'd be happy to help split the patches into individual PRs and
> > >> work on
> > >> >> >> > getting them merged. Please let me know how you'd like to
> > >> coordinate.
> > >> >> >> >
> > >> >> >> > Best regards,
> > >> >> >> > Abhishek
> > >> >> >> >
> > >> >> >> > On Wed, Oct 14, 2026 at 9:09 PM Alin Jerpelea <
> > [email protected]>
> > >> >> >> > wrote:
> > >> >> >> >
> > >> >> >> >> please prepare the first patches and I will handle them
> > >> >> >> >>
> > >> >> >> >> Best regards
> > >> >> >> >> Alin J
> > >> >> >> >>
> > >> >> >> >> On Wed, 14 Oct 2026, 16:37 Alin Jerpelea, <[email protected]>
> > >> >> wrote:
> > >> >> >> >>
> > >> >> >> >> > Hi,
> > >> >> >> >> >
> > >> >> >> >> > I can lend a hand tomorrow
> > >> >> >> >> >
> > >> >> >> >> > Thanks for your message
> > >> >> >> >> >
> > >> >> >> >> > Best regards
> > >> >> >> >> > Alin
> > >> >> >> >> >
> > >> >> >> >> > On Wed, 14 Oct 2026, 11:18 Felipe Moura Oliveira, <
> > >> >> >> [email protected]>
> > >> >> >> >> > wrote:
> > >> >> >> >> >
> > >> >> >> >> >> Hello,
> > >> >> >> >> >>
> > >> >> >> >> >> I am away from my desk for the next few days. If no one
> > offers
> > >> to
> > >> >> >> help
> > >> >> >> >> by
> > >> >> >> >> >> this weekend, I will reach out to you so I can help you with
> > >> this.
> > >> >> >> >> >>
> > >> >> >> >> >> Regards,
> > >> >> >> >> >>
> > >> >> >> >> >>
> > >> >> >> >> >> *--Felipe Moura de Oliveira*
> > >> >> >> >> >> Linkedin <
> > https://www.linkedin.com/in/felipe-oliveira-75a651a0
> > >> >
> > >> >> >> >> >>
> > >> >> >> >> >> On Wed, 14 Oct 2026 at 10:48 <[email protected]> wrote:
> > >> >> >> >> >>
> > >> >> >> >> >> > Hello,
> > >> >> >> >> >> >
> > >> >> >> >> >> > I would like to ask someone to help me merge some patches
> > for
> > >> >> the
> > >> >> >> AVR
> > >> >> >> >> >> > architecture, DA/DB family. I have a series ready with
> > some
> > >> >> fixes
> > >> >> >> and
> > >> >> >> >> >> > some new features. Same as before, I don't have a Github
> > >> account
> > >> >> >> so I
> > >> >> >> >> am
> > >> >> >> >> >> > looking for someone who could open pull requests
> > >> >> >> >> >> >
> > >> >> >> >> >> > The series as a whole is available in my "nuttx.git"
> > >> repository
> > >> >> at
> > >> >> >> >> >> > git.kerogit.eu accessible through HTTP/S. The relevant
> > >> branch
> > >> >> is
> > >> >> >> >> named
> > >> >> >> >> >> > avrdx_ws2812_upstream .
> > >> >> >> >> >> >
> > >> >> >> >> >> > In its current form, the branch is not suitable for
> > merging
> > >> - it
> > >> >> >> would
> > >> >> >> >> >> > be more than one feature per one PR which is against the
> > >> >> >> contributing
> > >> >> >> >> >> > rules. My plan is, if someone decides to help, to split
> > the
> > >> >> series
> > >> >> >> >> into
> > >> >> >> >> >> > steps and merge these steps one by one. After one step is
> > >> >> merged, I
> > >> >> >> >> >> > would rebase the remainder on current master branch and
> > >> provide
> > >> >> >> next
> > >> >> >> >> >> > step. I also plan to prepare text to be filled in the PR
> > form
> > >> >> >> >> >> > (essentialy doing as much as possible to make the job
> > easier
> > >> for
> > >> >> >> the
> > >> >> >> >> >> > person who will interact with Github.)
> > >> >> >> >> >> >
> > >> >> >> >> >> > There are four features:
> > >> >> >> >> >> >
> > >> >> >> >> >> > 1. fixes - build failure introduced between 13.0 and 13.1,
> > >> >> >> documenting
> > >> >> >> >> >> > performance regression between these versions and some
> > minor
> > >> >> stuff
> > >> >> >> >> >> > 2. zero latency interrupt support -
> > >> >> >> >> >> >
> > >> >> >> >> >> >
> > >> >> >> >> >>
> > >> >> >> >>
> > >> >> >>
> > >> >>
> > >>
> >
https://nuttx.apache.org/docs/latest/guides/concurrency/zerolatencyinterrupts.html
> > >> >> >> >> >> > 3. software interrupt emulation
> > >> >> >> >> >> > 4. lower half for WS2812 driver
> > >> >> >> >> >> >
> > >> >> >> >> >> > Thanks
> > >> >> >> >> >> >
> > >> >> >> >> >>
> > >> >> >> >> >
> > >> >> >> >>
> > >> >> >>
> > >> >>
> > >>
> >
