Battery level measurement with Olimexino 32U4

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Hi,

Just a simple question... is there any way for measuring the battery level with Olimexino 32U4? I have a datalogging system developed which is powered with D batteries and I guess there is some built-in solution to monitor their level.

The other option, of course, is using one of the analog inputs for that purpose but I hope there is a direct way to get the level without adding other elements....

Thanks in advance!