This is mostly implemented in a new ovms_partitions.{h,cpp} in ovms_ota component, with only minor extensions to ovms_ota itself. I have removed the ‘factory’ commands from ovms_ota if the new partition layout is detected at boot.

One big ‘gotcha’ I found was that we need to set CONFIG_SPI_FLASH_WRITING_DANGEROUS_REGIONS_ABORT= and CONFIG_SPI_FLASH_WRITING_DANGEROUS_REGIONS_ALLOWED=y in our sdkconfig - otherwise the partition table cannot be re-flashed.

The partition table must also be held in internal (not external SPI) RAM - which is about a 4KB overhead just for these checks.

The usual app-flash still works (and now targets the first OTA at 0x0010000, rather than factory), so this approach seems feasible and workable now. Once we are happy with this, and have a production firmware supporting this layout, I can also provide a new partitions.bin to the factory for new units to ship with.

I have a few minor enhancements to make: (a) add a ‘yes/no’ (like factory reset), (b) an option to load partition table in internal/external ram (internal only at the moment), and (c) some minor tidy-ups. I suggest then to just check it in with this basic manual functionality that can be experimented with. Absent any comments / suggestions, I should be able to commit this early in the coming week.

Regards, Mark.

P.S. OVMS v2 had to fit in 96KB of flash ;-)

On Jan 21, 2026, at 11:12 AM, Mark Webb-Johnson <mark@webb-johnson.net> wrote:
Michael,

The links are very helpful.

I have some time, and inclination to handle this (now that my new home build host is up and running and a make of OVMS from clean, with 32 cores and a fast SSD, is under 25 seconds).

real 0m24.642s

user 5m50.376s

sys 0m38.276s
We’ve already got the ‘ota copy’ command, so I will start with trying to work on manipulation of the partition table and improving the ‘ota status’ command to show partition table format and sizes.

Regards, Mark.
On 11 Jan 2026, at 5:34 PM, Michael Balzer via OvmsDev <ovmsdev@lists.openvehicles.com> wrote:
Signed PGP part
On the migration tool for changing the partition table from a running application, we're (of course) not the first having that issue.

If we're about to go that way, here is an implementation of the process:

Explanation: https://johnmu.com/2024-esp32-partition-update/

Source: https://github.com/softplus/Esp32Repartition

It's written for the Arduino IDE with the PlatformIO lib to create a UI, but the core function is straight forward and should be adaptable for us.

The implementation allows for direct manipulations of the partition table, i.e. doesn't need a prepared table blob to flash.

Using a prepared blob should be even more simple, basically just a matter of `spi_flash_erase_range()` & `spi_flash_write()` (→https://github.com/softplus/Esp32Repartition/blob/main/src/part_mgr.cpp#L297). We probably don't even need `getPartitionTableAddr()`, as our table is fixed at 0x8000.

The code needed is small. When using a blob, the table in theory uses a full flash sector of 4096 bytes, but probably doesn't fill the whole sector.

Regards,
Michael

Am 08.12.25 um 07:01 schrieb Mark Webb-Johnson via OvmsDev:
Michael, Carsten,

I think that if targeting things to cull, we would need to be balance size vs importance. For example, the RE tools mentioned is just 10KB total size. By comparison TPMS is 9KB, and web server is 538KB.

We learned with OVMS v2 that the biggest culprits in the long-run are always the vehicle modules. The core system stays pretty stable, but the space required for *all* vehicle modules grows with the number of vehicles supported.

I don’t think we can simply switch to 32MB flash, as that would abandon the existing users. We would also need to source a standard certified 32MB module (which I don’t think Espressif offer themselves).

Looking at the partition table:

# OVMS 16MB flash ESP32 Partition Table

# Name, Type, SubType, Offset, Size

nvs, data, nvs, 0x9000, 0x4000

otadata, data, ota, 0xd000, 0x2000

phy_init, data, phy, 0xf000, 0x1000

factory, app, factory, 0x10000, 4M

ota_0, app, ota_0, , 4M

ota_1, app, ota_1, , 4M

store, data, fat, , 1M

Assuming we could (and that is a big assumption given our older SDK) change that at runtime, then a possible migration path could be:

Have our code support both old and new partition table formats, and refuse to update to old format if firmware > 4MB. Get that code out into the hands of users.

Provide a migration tool for partition table:

Copy running code to factory (from ota_0 or ota_1, whichever is current).

Reboot

Change partition table (most likely replacing the entire table with a binary blob of the new format)

factory 4MB -> ota_0 same offset, 6MB size

ota_0 -> ota_1 6MB offset, 6MB size

Change boot to ota_0.

Reboot

Liase with factory so new modules use new partition format (and ship with firmware that supports it).

Wait a reasonable time for users to update before releasing any firmware > 4MB.

That would work more similarly to other more modern ESP frameworks which don’t bother with ‘factory’. It would allow us another 50% expansion. But it does run the risk of bricking (requiring espflash to recover) during the process.

But longer-term, the solution to me seems to be to allow the vehicle module code to overlay - so only the single vehicle you choose is loaded. And (absent any dynamic linking of modular code in freertos), the only straightforward way of doing that I know of is migrating vehicle support to Javascript (which comes along with a host of other advantages - most notably not having to be a C++ embedded developer to add/refine vehicle support).
Regards, Mark.
On 7 Dec 2025, at 4:39 PM, Carsten Schmiemann via OvmsDev <ovmsdev@lists.openvehicles.com> wrote:
Hi Michael,
It was to be expected that we would eventually run out of flash storage. That’s why I would immediately question whether we should detach ourselves from components that aren’t really being used. We could even start a survey or something like that.

For example, the RE tools — the idea behind them is great, but without documentation they’re not easy to use, and every time I tried to work with them, it just resulted in crashes.

Then there’s the question of who actually uses Telnet, SSH, the Duktape framework, the DBC parser, OBD2ECU, or CANopen (yes, the Twizy integration is the only one that uses it).

All great ideas, but in the end, how many users really make use of them?

The fewer active components we have to maintain, the ‘easier’ it would also be to port the code to a more current ESP-IDF version — and that would bring significant benefits such as improved networking features, including firewall capabilities and a much more stable switching between LTE and Wi-Fi. I’ve looked at llanges attempts and it’s extremely tough.

As an example, in my own custom firmware builds, I don’t enable the components (and of course not all vehicles, so not 100 percent representative) mentioned above. This requires small modifications in the code because, for example, the ESP logger is missing but referenced in another file, etc. But my firmware file is only about 2.8 MB.

Just my 2 cents

Carsten
Am 07.12.2025 um 08:57 schrieb Michael Balzer via OvmsDev <ovmsdev@lists.openvehicles.com>:
FYI: use `make size-components` to create a report on all component sizes (`make size-files` for source file level).

Unsurprisingly the webserver is on top, even with all assets precompressed already.

Top 10 components:

Per-archive contributions to ELF file:
  Archive File DRAM .data & .bss IRAM Flash code & rodata Total
libovms_webserver.a 0 255 0 134342 399846 534443
libstdc++.a 149 5640 0 141045 72513 219347
libmain.a 15 2104 0 139216 40086 181421
  libduktape.a 0 0 0 141641 20367 162008
libvehicle_renaulttwizy. 0 29 0 86517 75357 161903
libc-psram-workaround.a 1854 66 18391 118283 10943 149537
liblwip.a 17 3873 0 118366 16722 138978
libnet80211.a 938 9042 10475 92339 21900 134694
  libmbedtls.a 100 560 76 107079 26785 134600
  libvehicle_vweup.a 8 8 0 60846 43432 104294

Vehicles:

Per-archive contributions to ELF file:
  Archive File DRAM .data & .bss IRAM Flash code & rodata Total
libvehicle_renaulttwizy. 0 29 0 86517 75357 161903
  libvehicle_vweup.a 8 8 0 60846 43432 104294
libvehicle_mgev.a 156 26 0 47756 33998 81936
  libvehicle_smarteq.a 82 15 0 59267 19527 78891
  libvehicle_smarted.a 0 9 0 48481 28801 77291
libvehicle_renaultzoe_ph 4 10 0 44622 29564 74200
  libvehicle.a 0 68 0 57735 12062 69865
  libvehicle_bmwi3.a 0 2 0 33370 14357 47729
libvehicle_minise.a 9432 2 0 35360 2210 47004
libvehicle_hyundai_ioniq 176 7 0 32921 13425 46529
libvehicle_nissanleaf.a 0 3 0 35491 8941 44435
  libvehicle_kiasoulev.a 240 9 0 32508 5473 38230
  libvehicle_kianiroev.a 108 7 0 24070 4006 28191
libvehicle_mitsubishi.a 0 5 0 21645 3893 25543
libvehicle_boltev.a 0 5 0 15999 7864 23868
  libvehicle_niu_gtevo.a 4 12 0 18248 3733 21997
libvehicle_maxus_edelive 156 3 0 10713 7477 18349
libvehicle_renaultzoe.a 0 6 0 14828 2859 17693
libvehicle_maxus_euniq56 156 3 0 8363 6840 15362
libvehicle_voltampera.a 0 5 0 13221 1932 15158
libvehicle_hyundai_ioniq 0 3 0 11081 3191 14275
libvehicle_teslaroadster 0 6 0 10367 2238 12611
  libvehicle_thinkcity.a 0 3 0 6114 3449 9566
libvehicle_jaguaripace.a 0 8 0 5445 3941 9394
libvehicle_fiatedoblo.a 0 2 0 4262 2126 6390
libvehicle_teslamodels.a 0 2 0 5361 948 6311
libvehicle_toyotarav4ev. 0 2 0 5023 1255 6280
  libvehicle_maxus_t90.a 0 3 0 2567 2204 4774
  libvehicle_byd_atto3.a 0 2 0 3503 947 4452
libvehicle_energica.a 0 1 0 3319 880 4200
libvehicle_demo.a 0 2 0 3205 795 4002
libvehicle_maxus_euniq6. 0 2 0 2470 1182 3654
  libvehicle_fiat500.a 0 2 0 2838 732 3572
libvehicle_zombie_vcu.a 0 4 0 1882 1259 3145
libvehicle_mercedesb250e 0 2 0 2113 955 3070
libvehicle_zeva.a 0 2 0 2209 688 2899
  libvehicle_dbc.a 0 2 0 1278 1395 2675
libvehicle_cadillac_c2_c 0 7 0 1293 1105 2405
libvehicle_maple60s.a 0 2 0 1416 698 2116
libvehicle_chevrolet_c6_ 0 2 0 1053 1049 2104
  libvehicle_obdii.a 0 2 0 957 1007 1966
libvehicle_teslamodel3.a 0 2 0 458 713 1173
libvehicle_none.a 0 2 0 418 684 1104
  libvehicle_track.a 0 2 0 416 680 1098

Regards,
Michael

Am 06.12.25 um 10:33 schrieb Michael Balzer via OvmsDev:
Everyone,

with the latest vehicle additions, the firmware size has now grown to 4,015,328 bytes in build 3.3.005-485-gc4664881.

Our flash partitioning scheme is currently designed to provide three firmware partitions (factory, ota_0 & ota_1) of 4MB = 4,194,304 bytes each.

So we've now got 178,976 bytes = ~4% left.

Options beyond the 4 MB limit:

a) split features, e.g. vehicle support, into two or more builds

b) repartition into two firmware partitions of 6 MB each, reusing the factory partition for OTA

c) switch to an ESP32 WROOM module with 32 MB flash (possible?)

We've got some time left, new vehicles normally don't need that much space, I just wanted to raise awareness.

Regards,
Michael
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