Bootloader OTA bug with IDF V3.0 development versions (master branch)

[ESP_Angus]

Folks,

We've just noticed a fairly subtle but serious bug in the bootloader that was present in IDF during the V3.0 development cycle, between commit 969f1bb9b (version v3.0-dev-265-g969f1bb9b) and commit 11a87ca81 (version v3.0-dev-514-g11a87ca81).

These commits are from August 15 and September 5, respectively.

The bug is in the bootloader and causes OTA to stop applying changes after 15 updates. A manual reflash of an updated bootloader is required before any more OTA updates can be made.

Normally we don't comment on bugs found on the "bleeding edge" master branch during development, but this one is a little different as it's both subtle and effects the OTA update mechanism.

The IDF master branch does undergo automated testing before it's pushed to github, but for fully tested and stable versions to use in production we strongly recommend using a stable release. (The current stable release is V2.1, V3.0 is still forthcoming.)