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 2019 Microchip Technology Inc.DS00003084A-page 1

TABLE OF CONTENTS

1.0Introduction .................................................................................................................................................................1

1.1SAMA5D3 Xplained Board ...............................................................................................................................2

1.2SAM Boot Assistance (SAM-BA) ......................................................................................................................2

1.3Putty Terminal Program .................................................................................................................................... 3

1.4Github Repository – maXTouch_linux ..............................................................................................................4

2.0Building the source and setting up the tools ................................................................................................................ 5

2.1Device Tree Files .............................................................................................................................................. 5

2.1.1at91-sama5d3_xplained_dm_pda4.dtsi ................................................................................................5

2.1.2at91-sama5d3_xplained_pda4.dts .......................................................................................................5

2.2Configuring the Kernel Options .........................................................................................................................5

2.3Loading the Touch Driver as a Module ............................................................................................................. 6

2.4Building the Kernel ............................................................................................................................................ 6

2.5Modifying the U-boot-env.txt File ......................................................................................................................7

2.6Programming the SAMA5D3 Xplained Board ...................................................................................................8

3.0maXTouch Linux Driver ............................................................................................................................................... 9

3.1 I2C Driver – atmel_mxt_ts.c .............................................................................................................................. 9

3.2Object-based Protocol ......................................................................................................................................9

3.3Power Up and Reset .........................................................................................................................................9

3.4Downloading the Configuration .........................................................................................................................9

3.4.1triggering configuration download with sysfs ......................................................................................10

3.4.2Automatically downloading the configuration on driver probe ............................................................10

3.5Firmware Upgrade ..........................................................................................................................................10

4.0Debugging the Driver ................................................................................................................................................12

4.1Enabling Driver Debug Messages – dev_dbg ................................................................................................12

4.2Viewing Touch Events – evtest .......................................................................................................................12

4.3Viewing Touch Events – Android getevent .....................................................................................................13

4.4Debug File System Interface – sysfs ..............................................................................................................14

4.4.1mem_access ......................................................................................................................................15

4.4.2debug_enable .....................................................................................................................................15

4.5Improved Debug Interface ..............................................................................................................................15

4.6The mxt-app Utility .......................................................................................................................................... 15

Appendix A. Revision History ..............................................................................................................................................18

1.0 INTRODUCTION

This application note introduces the maXTouch Linux driver, its features and available debug options to help developers

with driver integration. It also provides details on how to configure and build the kernel on a test platform.

The maXTouch Linux driver is designed to support the Linux input subsystem. This driver resides in the drivers/input/

touchscreendirectory of the kernel and interfaces with the hardware to generate 2D touch events to the Linux input

subsystem.

The Linux driver can be compiled as an in-built driver or as a module to be loaded after the initial kernel boot. The

application note provides details regarding function of the driver and the debug options that are available through the

touch driver along with information regarding the testing of the touch driver.

This application note assumes that the user has a Linux based PC (either actual or a virtual machine) and has basic

knowledge of the Linux OS. It also assumes basic use of Github. All testing has been done using the Ubuntu OS version

16.04. Any critical libraries or tools that need to be installed will be mentioned in this application note.

The details within this document will mainly reference the standard Linux kernel. Where possible, differences between

the Linux “distributions” (for example, Ubuntu, Android) in terms of tools, directory locations or behavior will be noted.

AN3084

Using the maXTouch Linux Driver

Produktspecifikationer