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Fixme.ch:OldWiki/Magnetic Cards

719 bytes added, 00:51, 2 May 2015
=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.[https://www.raspberrypi.org/forums/viewtopic.php?f=2&t=5219]

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


=Liens divers=

http://bit.ly/lf1XQY

http://bit.ly/lE5NaZ
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