ESP32 Forum

luisonoff wrote: ↑

Fri Aug 30, 2019 12:48 pm

Hello, I just wanted to share my findings about this topic of updating partition table through OTA, for future users who fight this.

I faced this problem because we wanted to change partition table from FACTORY+OTA to OTA0+OTA1, plus we wanted to expand NVS partition size.
We got several devices already installed on clients, plus our devices' case is not easy to open, so we decided to do everything thru OTA.

I read many posts about this, but I just found the same answer: it is not recommended to change partition table from active app.
But I didn't know if it was possible or not at all.
We tried and tested and I can tell you partition table update thru OTA is doable.

We used SPI Flash driver, esp_partition and esp_ota from IDF.

These are the steps we followed in order to get it done:
1. Decide what partition table we wanted for the long term, in order to not change it again if possible.
2. Compile any app with this partition table, so we can find partition.bin in the build directory.
3. Attach this partition.bin to our app, adding this file to our project folder and using COMPONENT_EMBED_FILES in component.mk.
4. Modify our code in order to create a new app version that would be used for this update.
5. Device performs OTA firmware update of this new app.
6. This app checks after boot if factory partition exists, if it exists, then it is the old partition table.
7. If the old partition table is found, app downloads to RAM this same binary from server, and copies it to the new partition using its address (does not exist yet). This partition must not overlap with the actual running partition.
8. After copy bin to memory, app erases old partition table (address 0x8000), and copies new partition table in same place.
9. Then the location of new partitions NVS, otadata, etc is erased. Make sure they do not overlap with current partition.
10. Then we restart ESP, because new partition table is not loaded until restart.
11. After restart ESP tries to start each app partition, probably some of them will fail, but at the end it will find the correct one where we copied the bin file directly.
12. Then it starts from there, checks partition table, no factory partition exists, so partition table update is finished.
13. We do one more step for correctness, after detecting that the new partition table is used, we perform a new OTA now just using the library from IDF. This OTA works ok and we are done.
14. Last we modify our app code with the new partition table and (optional) we delete every code related to this partition table update.
15. We can continue developing with new partition table and every device is updated.

TIPS:
DO THIS AT YOUR OWN RISK
TEST EVERYTHING with developing units before trying the real ones.
Before writing to flash it is necesary to erase first.
After writing partition table it is necessary to restart ESP in order to load it and be able to detect partitions.
Before restart make sure you have a correct bin written to where the new partition table expects.
Be careful not to write or erase any memory address that overlaps your current partition.
In order for all this to work, you have to change menu config option, in Components/SpiFlashDriver select Allowed in "Writing to dangerous flash regions".

These are the functions we used, just for reference:

Code: Select all

error = spi_flash_read(address, buffer, size);
error = spi_flash_erase_range(address, sizeToErasemultipleof4096);
error = spi_flash_write(address, downloadedFile, downloadedFileSize);
esp_partition_t * partition = esp_partition_find_first(ESP_PARTITION_TYPE_APP, ESP_PARTITION_SUBTYPE_ANY, "factory");
if (partition != NULL)
{
// partition factory found
}
esp_ota_set_boot_partition(partition); //we didn't use this one at all