<blockquote>
<blockquote>
<p>I'm not familiar with STM32, but googling around seems to indicate that it has the ability to be woken up from the UART. If that is the case then it is something that should be addressed by the periph implementation.</p>
</blockquote>
<p>This usually loses the first byte, which may or may not be acceptable.</p>
</blockquote>
<p>Is that due to taking too long to wake up and clear the receive buffer or is it actually a documented hardware limitation? I don't think I've ever had to tolerate that problem on any platform, but it's possible I've avoided it by shortening the wakeup sequence.</p>
<p>I recall some time ago moving the main oscillator startup to a later point and making it conditional, but I don't remember if that was for the uart or just to avoid wasting power for xtimer overflow wakeups which come very frequently on EFM32.</p>

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