Cache disabled but cached memory region accessed
What it looks like
Guru Meditation Error: Core 0 panic'ed (Cache disabled but cached memory region accessed).
What it means
An interrupt ran while the flash cache was turned off, which happens while flash is being written (Preferences, LittleFS, SPIFFS, OTA). The handler, or something it called or read, lives in flash, so it could not be fetched.
Likely causes
- An interrupt handler without IRAM_ATTR.
- A handler that calls a function without IRAM_ATTR.
- A handler that reads a const table, which is stored in flash.
How to fix it
- Mark the handler and every function it calls IRAM_ATTR.
- Move constant data the handler reads into RAM: drop const or copy it to a RAM buffer at start-up.
- Do as little as possible in the handler: set a flag and return.
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