How to automatically flash Arduino using HEX firmware located on a microSD card?

Question

Arduino

Prompt articles with ready-made examples of using a microSD card as a container for updating Arduino firmware. I think it should happen like this:
1. Arduino starts or restarts.
2. Finds update.hex on the memory card
3. Updated, deletes the file.
4. Reboot again.
If there is no update file, the main program starts.
Appeal to the habra community, write such an article, if it does not exist yet, I think it will be very useful.
Thank you.

Answer 1

https://github.com/thseiler/embedded/tree/master/a...
this is a bootloader for arduino that supports downloading firmware from an SD card and, as usual, via a serial port (via USB) also supports