Read LAST_FATAL_ERROR.md

You will find and interpret the `LAST_FATAL_ERROR.md` file on an atfs device's boot partition.

This page only applies when you deploy to an SD-card device.

If the file exists, remove the card and put it in any Mac, Windows, or Linux computer. The boot partition, labelled atfs-boot, uses plain FAT32, so it opens like any USB stick. You need no special software. Open LAST_FATAL_ERROR.md in any text editor. It reads as plain text, with a small block of details at the top.

• The file keeps only the latest issue. If the device has failed more than once, you see the most recent failure only.
• The device deletes the file automatically once it runs successfully for a short time after a restart. If the file returns after that, a new fault has occurred.
• The timestamp field is often incorrect, and says so itself. These boards have no battery-backed clock, so each board reads the date as 1970 until it reaches the internet and corrects itself. The uptime field (how long the device had run) and the boot field (which boot attempt this was) stay accurate regardless. They are the more useful numbers if you want to tell “died instantly” from “ran for days first”.

The block at the top of the file names an error_code. Look it up in the atfs error codes reference first. If you do not find it there, check the system error codes reference.