Diagram SOlution

Generally for connecting an LCD display to an Arduino using 7 strands, it usually breaks the leg that has any projects that remain few ports to be used. But there is a way, using an IC 74LS164 (8-bit serial shift register), a resistor and a diode, but its not just hardware, you have to use a library.

This Arduino library for connection of 2-wire or 3-wire using HD44780 compatible LCD display via shiftregisters. This circuit is considered "deprecated", but its worth testing.