Shifting a 2.7V digital signal to Arduino logical levels?
Arduino inputs must meet  the specified logic levels for margin.

VIL &lt;= 0.3Vcc max
VIH >= 0.7Vcc min

Thus the input square wave must be >= 0.4Vcc  and for 5V , or 0.4 * 5 = 2.0 Vpp    and you have 2.7V with 0.7V margin.

Alternatively you may AC couple to input with R bias to Vcc/2.

There are lots of level shifter solutions for 2.7V to 5V.

Rev B.






simulate this circuit &ndash; Schematic created using CircuitLab


assuming noise free supply and signal.