Fixme.ch:OldWiki/Magnetic Cards

=Raspberry pi (CMOS <- TTL level voltage attenuation)=

The "level converter" in this case is only needed to convert from 5V to 3V3 levels, and can consist of a simple voltage divider. the 3V3 level from a CMOS output needs no conversion for most 5V inputs.

You can create a simple attenuator to 3V by using a top 2K2 (2.2k) and a bottom 3K3 resistor, it will work even at high speeds, because the GPIO input is high impedance and its capacitance is relatively low, so the signal isn't degraded much.

2K2 5V in ——/////—+— 3V out 3K3 | GND —–/////—-

=Liens divers=

http://bit.ly/lf1XQY

http://bit.ly/lE5NaZ