If your 3.3V device inputs are not 5V tolerant and your 5V inputs lack 3.3V compatible thresholds then sadly you won’t be able to interface them across voltage levels without a shifter circuit.

If your arrangement is different, or you’re experiencing a problem, you will want a level shifter circuit. At their simplest, two N-FETs like 2N7002 will do wonders. If you want smaller PCB ...

All this leads to significant increases in power consumption and die size. The proposed circuit is a single supply level shifter to translate the signal from one power domain to another power domain.