How to use Matrix Keypad

Overview

A matrix keyboard can be used as an input device in different applications.

Use cases:

• Keypad in handheld devices.
• Access control systems, for keying in ID number and password, etc.
• Low-end point of sale terminals which are not equipped with touch screen interface.
• and many more..

This tutorial demonstrates how to interface 4x4 matrix keypad with Toradex module & Iris Carrier Board V1.1 A.

Schematic diagram

Image of keypad used:

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Schematic diagram:

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Demo application in C

• Download demo code from the Download Section.
• Build and deploy the application.
• Navigate to My Device > Program Files > matrixkeypad_demo and run the application matrixkeypad_demo.exe.

Demo application in CSharp

• Demo application can be downloaded from the Download Section.
• Navigate to Solution Explorer in visual studio > Right Click on Solution > Properties > Devices.
• Uncheck "Deploy the Latest version of the .NET Compact Framework (including Service Packs)".
• Build and deploy the application on your WinCE device.
• Download and Install .NET Compact Framework directly to the FlashDisk of the device from here.
• Go to My Device > Program Files > vcsharp_matrixKeypad_demo and run the application vcsharp_matrixKeypad_demo.exe.

Following GUI will open. Press Start Scanning button to start the scanning.
A box on output window will glow with green color on pressing respective button on matrix keypad as shown below.

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Download Section

• Native C Demo - PXA/Tegra and Vybrid/iMX6.
  
• CSharp Demo   - PXA/Tegra and Vybrid/iMX6.

Note: For better results, keybd_event function can be used to keep the current status of the keys and synthesizes a keystroke. It may be useful to implement debouncing and to generate actual key strokes, allowing the matrix keyboard to behave like a regular one. This will also support auto-repeat and other typical keyboard behaviours. For more information, check this MSDN article.