How to connect two arduino board, one connect to keypad and one connect to lcd

[DaveX]

@vayne

i have a project to make something with 2 arduino board. So i want to make keypad password with lcd, can someone help me how to connect arduino 1 board that connect to keypad, and the other one that connect to lcd ?

Maybe start by making a plain keypad example work on one arduino, and a plain LCD example work on the other, and then consider what you want to communicate. Simplest would be to check the password on the keypad arduino and then send only a 1-bit LOCKED/UNLOCKED signal to the LCD arduino. If you want more features than that, you need to send more data, and it is much more complicated.

If you want the LCD Arduino to parse some serial and act, perhaps look into some of these erial communication and parsing examples:

@DaveX

Communication

• ASCII Table tutorial
  • Simulation -- Prints a table of characters in decimal, hex, octal, and binary.
• Create a LED Dimmer tutorial
  • (communicates in Binary with processing, not simulated)
• Create a Graph with Processing tutorial
  • (communicates in Binary with processing, not simulated)
• MIDI Note Player
  tutorial
  • (Writes MIDI codes to the serial port, not simulated)
• Use Multiple Serial Ports on the Arduino Mega
  tutorial
• Physical Pixel tutorial
• Read ASCII String tutorial
  • Simulation parses 3 integers from Serial to drive an RGB led.
• Serial Call and Response (handshaking) tutorial
• Serial Call and Response (handshaking) with ASCII-encoded output tutorial
  • Simulation -- Reports sensor data to Serial when prompted.
• SerialEvent tutorial
  • Simulation -- Demonstrates serialEvent() to collect a line without blocking. (could use serialAvailable())
  • See also: Serial Input Basics - updated and @nickgammon on Serial
• SerialPassthrough tutorial
• Virtual Color Mixer tutorial

@DaveX

Non-Arduino Serial communication simulations:

Serial Input Basics by @Robin2

• Example 1 -- Receiving single characters.
• Example 2 -- Receive several chars with an end marker.
• Example 3 -- Receive with start- and end-markers
• Example 4 -- Receiving a single number from the Serial Monitor
• Example 5 -- Receiving and parsing several pieces of data
• Example 6 -- Program to receive binary data

How to process incoming serial data without blocking by @nickgammon

• Example 1: Non-blocking line buffering -- Non-blocking line buffering
• Example 2: Serial parsing state machine -- state-machine for parsing commands. E.g. R4500S80G3

Misc

• Serial parsing RPN/Postfix:
• pcRead by @gcjr -- one-character parsing diagnostic/control tool (w/ Simulation).
• Good Forum thread on parsing a line into tokens with strtok()
• My adaptations of @nickgammon's state-machine parser into a switch-case single-letter post-fix parser for commands and numbers. E.g. 4500R 80S 3G or '123 24 /p`:
  • V1: Simple RPN number and command parsing and
  • V2: RPN 4 function calculator+commands
  • V3: Serial control of Stepper speed, acceleration and motion control with RPN calc -- Use Serial to control a stepper with real-time adjustment of Acceleration, Maximum speed and Position, with 4-function calculator.
• txtZyme (github) with Wokwi sim of txtZyme modified for Stepper Motor