Hab gerade gelesen, dass die AVRs interne Begrenzungsdioden haben. Diese werden bei Vcc+0,5V bzw -0,5V leitend, zusammen mit einem genügend großen Vorwiederstand kann man also fast jedes Signal direkt auf den Pin geben.

MfG

Zitat Zitat von Eine Atmel Appnote
"To protect the device from voltages above VCC and below GND, the AVR
has internal clamping diodes on the I/O pins. The diodes are connected
from the pins to VCC and GND and keep all input signals within the
AVR’s operating voltage.
Any voltage higher than VCC + 0.5V will be forced down to VCC + 0.5V
(0.5V is the voltage drop over the diode) and any voltage below GND -
0.5V will be forced up to GND - 0.5V.
By adding a large resistor in series, these diodes can be used to
convert a high voltage
sinus signal down to a low voltage square wave signal, with amplitude
within the AVR’s
operating voltage ± 0.5V. The diodes will thus clamp the high voltage
signal down to the
AVR’s operating voltage."