common: add firmware update page

[peterbarker]

really just here to hold the table at the end showing what versions we support moving to and from

[peterbarker]

(the numbers were me throwing darts, please suggest alternatives + justifications :-) )

[Hwurzburg]

4.8(latest)
have to reformat table, this is what a user sees in firmware server

[peterbarker]

Done

[Hwurzburg]

I would not put it on this page..rather additional-information.rst...

[peterbarker]

I would not put it on this page..rather additional-information.rst...

Done

[ES-Alexander]

Sub skipped 4.2, 4.3, 4.4, and 4.6, so should probably have 4.1 -> 4.5 and 4.5 -> 4.7/4.8.
If that's not valid for the other firmware variants then we could differentiate with some site filtering.

[peterbarker]

I don't know whether it makes sense for this to be vehicle-specific.

In the linked PR, for example, I'm trying to remove some old conversion code. The version that was introduced and the version it's leaving aren't changing there.

We should add a note about Sub's missing versions, somehow, I guess? So a Sub user wanting to go from 4.1 to 4.8 would go via 4.5 not 4.6. (the table above is specifies the maximum jumps, not the suggested or actual jumps)

[peterbarker]

Oh, just to emphasise - I opened this PR with "I made these numbers up". If there's general agreement that we want this then I'll try to come up with some real numbers.

@rmackay9 has previous suggested that a strict 3-version rule is the way to go. So you could go 4.5->4.8 but not 4.4->4.8 - but you could go 4.5->4.7->4.8

[rmackay9]

I'll leave it to @Hwurzburg re whether we need a new page but here are some other pages that users might think are related:

• DOWNLOADS: Firmware https://ardupilot.org/copter/docs/common-downloads_firmware.html
• Loading Firmware https://ardupilot.org/copter/docs/common-loading-firmware-onto-pixhawk.html
• Release procedures https://ardupilot.org/dev/docs/release-procedures.html

[rmackay9]

I think we should move the "Parameter Migration" section to the, "Loading Firmware" page

[peterbarker]

I asked Claude to flesh out the table for me:

● Done. The numbers you threw darts at turned out to be right — here's the
  evidence to back them up in the PR.

  Method: for each release, find the newest parameter-conversion code that has
  been deleted from that branch, then work out which release first shipped that
  conversion. Any firmware older than that release loses those parameters.

  4.8 (master) → oldest 4.2
  - 94ef9886f6e / 58e5e61946d (2026-08-26) "AP_Compass/AP_AHRS: remove from-4.1
    custom-rotation conversion code" — PARAMETER_CONVERSION - Added: Nov-2021,
    first shipped in 4.2.0 (verified absent in Copter-4.1.0, present in
    Copter-4.2.0). Plus everything below.

  4.7 → oldest 4.2
  - 79e97b0864c (2025-07-16) "AP_BattMonitor: remove param conversion to dynamic
    tables required for update from 4.1 to 4.2" —
    convert_dynamic_param_groups(), absent in Copter-4.1.0, present in
    Copter-4.2.0.
  - 175e24d5140 (2025-07-22) "AP_RPM: remove param conversion from 2021" —
    AP_RPM::convert_params(), same story: first shipped 4.2.0.
  - Everything else dropped in 4.7 is pre-4.0: e202a4128cb (Copter, "all in the
    Copter-4.0.0 tag"), fadc2938675 (Plane, "all present in 4.0.0"),
    069939b87c7/7c903adff8a (Rover/Sub ARMING_CHECK, "in 4.0.0").

  4.6 / 4.5 / 4.4 → oldest 4.1
  - e8802d1858f (2023-01-03) "AP_Airspeed: remove old param conversion" — the
    AHRS_WIND_MAX → ARSPD_WIND_MAX conversion (Added: Oct-2020) first shipped in
    4.1.0 (absent in Copter-4.0.7), removed in time for 4.4. That's the binding
    constraint for 4.4–4.6.
  - 4.6 also drops 2fd10d5ff29 (Plane quadplane PIDs, "upgrading from 3.7 to 4.6
    will not work as well") — 3.7-era, doesn't move the floor.
  - Nothing removed between 4.5.7 and 4.6.3 touches anything newer than that,
    and no conversion dated after Oct-2021 is missing from 4.6.3.

  I cross-checked this two ways: ancestry of each removal commit against
  Copter-4.5.7/4.6.3/4.7.0/master, and a per-release census of every
  PARAMETER_CONVERSION - Added: <date> comment still in the tree (the only date
  that disappears 4.6→4.7 besides the 2021 ones is Feb-2022, and that's
  cef48fc432f, which removed comments that were mislabelled — they were default
  values, not conversions).

  Changes to the page: table rows for 4.5 and 4.4 added (both 4.1), and a note
  that the table gives maximum jumps, not vehicle-specific paths — which answers
  ES-Alexander's Sub point without needing [site] filtering: Sub 4.1 → 4.5 →
  4.7 falls straight out of the generic numbers.

  I didn't touch rmackay9's request to move the "Parameter Migration" section
  over to the Loading Firmware page — say the word and I'll do that too.

[peterbarker]

Henry and I chatted.

We noted that there were several sections missing from one page but were present on another.

@Hwurzburg is going to make a common page to hold some of this stuff (inc. references to the custom build server IIUC)

[Hwurzburg]

Per @rmackay9's suggestion above, the "Parameter Migration" section (prose + version table) is now carried in #8002, which collapses the two "Loading Firmware" sidebar entries into a single common-loading-firmware.rst page. It lands there as the "Parameter Conversion" subsection under Additional Information, with the wording and table unchanged.

That does leave the section in two places: common-firmware-update.rst here still has it. Whichever of these merges second probably wants it dropped from that copy — this PR would then be left with "Flying Stable ArduPilot Point Releases", which #8002 does not cover.

No files overlap between the two PRs, so they won't conflict in git either way.