XL keypad (not usual 3x4 or 4x4)

Projects General Guidance
1

Hi all,

I'm trying to understand how to implement a touch matrix with about 10x30 buttons.
First of all is it possible connect a so high buttons number?
Is it the right way to do it? I see there are serial interfaces, but after that I need to develope something like a controller..

Can someone give me any suggestions?

Thanks in advance

Andrea

2

40 IO pins - use a mega and the keypad.h library.
Don't know how responsive it will be with that many, I've only used it for 4x4.

3

Hi, thanks for your answer.
I'm new of arduino: can you explain me better what does it mean?
What is a mega? 40 IO Pins?

Thank you very much.
Andrea

4

squizzatoandrea:
Hi, thanks for your answer.
I'm new of arduino: can you explain me better what does it mean?
What is a mega? 40 IO Pins?

Thank you very much.
Andrea

The Mega is another Arduino development board with a different microcontroller chip than the Uno (the most common Arduino board). The main reasons to use the Mega instead of the Uno are the larger memory (both for program and RAM) and more I/O pins.

IO or I/O stands for Input / Output pins, these are pins that can function either as inputs or outputs (depending upon how they are configuring and used in a sketch).

5

I'll loot at that version.

Thanks

Andrea

6

Also, even though the basic keypad tutorial is written for the more common 3X4 keypads, the library it uses can be set for arbitrary numbers of rows and columns since you define the specific number for both in your sketch. Just keep track of which pins you use for a specific row or column and you shouldn't have any problems.

7

I think 300 keys is too many for one matrix to sense, especially for capacitive sensors. You will have to charge/discharge each sensor and complete sensing all of them within like 50ms or so to stay responsive.

8

@liudr, Where did capacitive sensors come into play? I don't see any mention of that.

I'm treating the request as the library driving 1 of 10 columns low, and reading the rows to see if any pin was pulled low by a button being closed.
Then back high and the next column low and the rows scanned, etc.

9

CrossRoads:
@liudr, Where did capacitive sensors come into play? I don't see any mention of that.

I'm treating the request as the library driving 1 of 10 columns low, and reading the rows to see if any pin was pulled low by a button being closed.
Then back high and the next column low and the rows scanned, etc.

OP said touch matrix so I assumed cap sensing. Could be resistive sensing or just a casual use of word.

BTW, will there be two or more buttons pressed at the same time? That is the biggest problem for simple keypad libs.