See how we can improve the error messages in bootloader

[peerst]

When mounting fails we only get a timeout message.

This is caused by the RTEMS media listener which waits for a SD card and then calls a callback.
Currently its unknown how we can differentiate between a timeout to detect a SD card and a mount error due to e.g. wrong filesystem types.

This needs some research or possibly extension to RTEMS media listener probably.