invalid header: 0xffffffff
What it looks like
rst:0x1 (POWERON_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT) invalid header: 0xffffffff invalid header: 0xffffffff
What it means
The bootloader looked for firmware and found none it could use. 0xffffffff is erased flash. The message repeats because the ROM keeps retrying.
Likely causes
- The flash is empty, for example after an erase or a failed upload.
- A .bin written at the wrong offset, such as an application image written at 0x0 instead of 0x10000.
- A flash mode or size setting that does not match the board.
How to fix it
- Upload again from the Arduino IDE, or flash the merged image at offset 0x0 with esptool.
- When flashing by hand, write the bootloader, partition table and app at their own offsets, or use a merged binary at 0x0.
- Try Tools > Flash Mode: DIO if QIO does not boot.
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