Signals and controls
SPI-capable logic level shifter
Translate logic between 5 V and 3.3 V devices.
What it does
A translator recreates a logic signal at the destination voltage. It must support the direction, speed, and signal type of the interface.
Connections and compatibility
For the RFID example, a 74LVC125A powered at 3.3 V can buffer four Uno outputs if that exact part specifies 5 V-tolerant inputs. Tie its enables low and add a 100 nF bypass capacitor.
Choosing one
Choose a documented fast push-pull translator or a ready-made SPI translator. The common BSS138 I²C converter is not a universal replacement.
Common mistakes
Power-supply regulation and logic translation are different. Confirm both before connecting a module advertised as supporting 5 V.
Use it in a tutorial
- Using an RFID module — Read an RC522 tag identifier with correct voltage translation, and understand why a UID is not a secure key.