Load Config File from SD Card And Use It with a 3.5" TFT LCD Touchscreen With Arduino UNO R3/R4

Overview

This repository contains a program to read a config file from an SD Card and use the data to change the program execution on an Arduino UNO R3/R4/Mega nad a 3.5" TFT LCD Shield, as shown below -

Most 3.5" TFT LCD Touch displays use the ILI9486 Display Driver and include a resistive touchscreen. The PCB Layout & silkscreen text may vary slightly between displays. This does not change their behaviour and functionality. This repository depends on the following libraries -

• Adafruit Touch Screen Library to manage touch input
• Adafruit GFX Library for graphics primitives
• This fork of the MCUFriend KBV library to drive the display (this makes it compatible with the UNO R4)

The program has been written using PlatformIO, and has been tested on the Arduino UNO R3, Arduino UNO R4 Minima & Arduino UNO R4 WiFi.

Tip

A detailed tutorial on how to use this repository is available at https://dumblebots.com/2024/07/02/using-3-5-tft-lcd-display-with-ili9486-arduino-part-3-text-files-sd-card/. The tutorial includes a comprehensive explanation of the code and how to use it.

Building/Uploading With PlatformIO

Since this project has been written using PlatformIO by default, simply run the following commands to fetch the libraries, build the project and upload the program -

pio pkg install
pio run
pio run --target upload

Building/Uploading With Arduino IDE

Create a new sketch and copy the contents of src/main.cpp from this repository into the default .ino file. Create a new tab/file in the IDE named constants.h and copy the contents of src/constants.h from this repository into this file.

Install the Adafruit Touch Screen Library and Adafruit GFX Library from the Library Manager (under Sketch>Include Library>Manage Libraries...)

Download this repository as a ZIP file and install it by navigating to Sketch>Include Library>Add .ZIP Library, and selecting the downloaded file from the file explorer.

After this, you can Build and Upload the program as usual.

Using the Example

As soon as the program is uploaded, the display should turn black and the following message should be printed on the display -

Next, create a file called CONFIG.TXT on a FAT formatted SD Card, which will be inserted into the SD Card slot on the TFT LCD Shield. The file must contain three color codes, which will be used to draw three squares on the display. Two examples are shown below -

Example 1

Config file -

square-1-color" = f800"
"square-2-color" = "07E0"
"square-3-color" = "001F"

Result -

Example 2

Config file -

"square-1-color"  =   "fFe0" // Yellow

"square-2-color" = "7ff" // Cyan
"square-3-color"  = "F81F" // Magenta

Result -

Tip

To create your own colors, see this guide.

Troubleshooting

Some common problems and their solutions -

Problem	Solution
Display stays white after uploading program	Non-Standard Driver (not ILI9486)
Display not responding after touch	Try changing the order of the touch pins in src/constants.h file, i.e. swap the values of XP, YP, XM and YM
Compilation issues related to SPI	Update the Arduino IDE version and/or install the SPI library
Display Flickering/Arduino is reset automatically	Faulty Power Supply/Cable