MarlinFirmware/Marlin

[FR] button multiplexing

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#22,726 opened on Sep 7, 2021

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C: User InterfaceT: Feature Requestgood first issue

Description

Is your feature request related to a problem? Please describe.

Button support has been added recently, but most motherboards don't have many pins free. Multiplexing will allow more buttons to be operated.

Are you looking for hardware support?

No response

Describe the feature you want

In the button configuration, I would like to be able to set the pins that support the buttons multiplexing. Like in the table below with pin names and button behaviour.

Screenshot_1

Additional context

No response

Contributor guide

Tech stack
cpp
Domain
backend
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
C++ programminghardware multiplexing basicsMarlin firmware structure
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30
Research direction
Start by understanding the existing button configuration code in Marlin's 'Marlin/src/module/endstops.h' or similar files. Review how pins are currently assigned and how button events are handled. Then design a multiplexing scheme that allows multiple buttons to share pins through a matrix or multiplexer IC. Look at how Marlin handles other multiplexed inputs like thermistors for reference. Finally, implement the configuration options (e.g., pin names and behavior table) and update the documentation.