Unidirectional Communcation between 2 Arduino boards

original article

   I want to send many commands using just 1 wire (and ground) so I use 2 Arduino boards.
   Base schematic for unidirectional communcication between Arduino boards is

and you can test this simple mode communication using info from article Tech Thurday #005: Arduino to Arduino Serial Communication.
   For sender (transmiter) I use a keypad with LCD1602 shield (see https://www.dfrobot.com/

This shield has the schematic

   Test schematic is

and sketch for transmiter is transmiter_v0.ino and sketch for receiver is receiver_v0.ino.
   If you have v.1.1 shield you must have

and for v.1.0

   I made Unidirectional Communication between 2 Arduino boards

  The states for this system are:
- all button are free (not pushed)

- if you push SELECT button

- if you push LEFT button

- if you push RIGHT button

- if you push UP button

- if you push DOWN button