Initializing and using xtimer before the kernel has initialized leads to a crash (no output, corrupted stack in gdb). I verified this for the Thunderboard Sense (EFM32) target and Seeeduino Arch Pro (LPC1768). I use it exactly the same as the Mulle board (#4133).

The problem does not happen when the delay is less than the backoff. So my workaround for sleeping 1ms is sleeping 100 times 10 µs.

Use case: The Thunderboard Sense has a I2C GPIO expander that needs 1ms of wakeup time. I address this GPIO expander to enable the sensors so they get initialized before auto_init().