arduino tft lcd 240x320 sd display bmp brands

I"m working on a project which uses a Elegoo 2.8" 240x320 TFT LCD display hardwired (breakout) to a Mega2560 Pro (mini) board. Everything works as expected, but the bmp image display draws extremely slowly on the screen, taking about 21 seconds to reveal, every time. My project displays several lines of text over top of the image, and also drives a 24 LED NeoPixel ring, which all work perfectly. I load the BMP upon power up as a background image one time, which takes 21 seconds, then everything works with very good speed thereafter. I"ve stripped my code down to only include the necessary lines to load and display the BMP. It"s pretty much the example code which came with the screen. Are there any obvious errors or changes I can make to improve the drawing speed of the image? Here is my code:

Hello, this tutorial is a follow up of the 2 other ones about the 2.4″ TFT LCD Shield with Arduino UNO, so the first one was about Interfacing and fixing the touch function problem also inverted axis, then the second one was about using simple function to draw different shapes and how to create a touch button to activate some functions…

But today we’re about the reading of images from SD card and showing them on the screen, first don’t forget to plug your SD card with your computer and format it as FAT32 then transfert your images don’t forget that they should be “BMP” format, Bitmaps 24 !! To have a correct image the resolutions should be 240*320, little explanation:

So you can chose whatever suits you, either change the screen rotation or the image rotation on your PC… then remeber or copy the image name and that’s it, plug your SD card in the shield.

Anyway now I commented that line, beacuse I am not interested in speed right now. But now the problem seems to be the programation code. the error message is as follows: ( I am using Arduino 1.8.7)

C:\Users\ADMIRAL\Videos\arduino\Libraries\Adafruit_ILI9341_AS\examples\ILI9341_draw_bitmap_v2\ILI9341_draw_bitmap_v2.ino:101:37: warning: ISO C++ forbids converting a string constant to "char*" [-Wwrite-strings]

C:\Users\ADMIRAL\Videos\arduino\Libraries\Adafruit_ILI9341_AS\examples\ILI9341_draw_bitmap_v2\ILI9341_draw_bitmap_v2.ino:106:42: warning: ISO C++ forbids converting a string constant to "char*" [-Wwrite-strings]

C:\Users\ADMIRAL\Videos\arduino\Libraries\Adafruit_ILI9341_AS\examples\ILI9341_draw_bitmap_v2\ILI9341_draw_bitmap_v2.ino:118:39: warning: ISO C++ forbids converting a string constant to "char*" [-Wwrite-strings]

C:\Users\ADMIRAL\Videos\arduino\Libraries\Adafruit_ILI9341_AS\examples\ILI9341_draw_bitmap_v2\ILI9341_draw_bitmap_v2.ino:121:42: warning: ISO C++ forbids converting a string constant to "char*" [-Wwrite-strings]

C:\Users\ADMIRAL\Videos\arduino\Libraries\Adafruit_ILI9341_AS\examples\ILI9341_draw_bitmap_v2\ILI9341_draw_bitmap_v2.ino:151:40: warning: ISO C++ forbids converting a string constant to "char*" [-Wwrite-strings]

C:\Users\ADMIRAL\Videos\arduino\Libraries\Adafruit_ILI9341_AS\examples\ILI9341_draw_bitmap_v2\ILI9341_draw_bitmap_v2.ino:163:39: warning: ISO C++ forbids converting a string constant to "char*" [-Wwrite-strings]

C:\Users\ADMIRAL\Videos\arduino\Libraries\Adafruit_ILI9341_AS\examples\ILI9341_draw_bitmap_v2\ILI9341_draw_bitmap_v2.ino:176:37: warning: ISO C++ forbids converting a string constant to "char*" [-Wwrite-strings]

C:\Users\ADMIRAL\Videos\arduino\Libraries\Adafruit_ILI9341_AS\examples\ILI9341_draw_bitmap_v2\ILI9341_draw_bitmap_v2.ino:183:38: warning: ISO C++ forbids converting a string constant to "char*" [-Wwrite-strings]

C:\Users\ADMIRAL\Videos\arduino\Libraries\Adafruit_ILI9341_AS\examples\ILI9341_draw_bitmap_v2\ILI9341_draw_bitmap_v2.ino:188:38: warning: ISO C++ forbids converting a string constant to "char*" [-Wwrite-strings]

C:\Users\ADMIRAL\Videos\arduino\Libraries\Adafruit_ILI9341_AS\examples\ILI9341_draw_bitmap_v2\ILI9341_draw_bitmap_v2.ino:193:38: warning: ISO C++ forbids converting a string constant to "char*" [-Wwrite-strings]

C:\Users\ADMIRAL\Videos\arduino\Libraries\Adafruit_ILI9341_AS\examples\ILI9341_draw_bitmap_v2\ILI9341_draw_bitmap_v2.ino:198:38: warning: ISO C++ forbids converting a string constant to "char*" [-Wwrite-strings]

C:\Users\ADMIRAL\Videos\arduino\Libraries\Adafruit_ILI9341_AS\examples\ILI9341_draw_bitmap_v2\ILI9341_draw_bitmap_v2.ino:205:39: warning: ISO C++ forbids converting a string constant to "char*" [-Wwrite-strings]

C:\Users\ADMIRAL\Videos\arduino\Libraries\Adafruit_ILI9341_AS\examples\ILI9341_draw_bitmap_v2\ILI9341_draw_bitmap_v2.ino:210:39: warning: ISO C++ forbids converting a string constant to "char*" [-Wwrite-strings]

C:\Users\ADMIRAL\Videos\arduino\Libraries\Adafruit_ILI9341_AS\examples\ILI9341_draw_bitmap_v2\ILI9341_draw_bitmap_v2.ino:215:39: warning: ISO C++ forbids converting a string constant to "char*" [-Wwrite-strings]

C:\Users\ADMIRAL\Videos\arduino\Libraries\Adafruit_ILI9341_AS\examples\ILI9341_draw_bitmap_v2\ILI9341_draw_bitmap_v2.ino:220:39: warning: ISO C++ forbids converting a string constant to "char*" [-Wwrite-strings]

C:\Users\ADMIRAL\Videos\arduino\Libraries\Adafruit_ILI9341_AS\examples\ILI9341_draw_bitmap_v2\ILI9341_draw_bitmap_v2.ino: In function "void drawBMP(char*, int, int, boolean)":

C:\Users\ADMIRAL\Videos\arduino\Libraries\Adafruit_ILI9341_AS\examples\ILI9341_draw_bitmap_v2\ILI9341_draw_bitmap_v2.ino:267:40: warning: converting to non-pointer type "int" from NULL [-Wconversion-null]

C:\Users\ADMIRAL\Videos\arduino\Libraries\Adafruit_ILI9341_AS\examples\ILI9341_draw_bitmap_v2\ILI9341_draw_bitmap_v2.ino: In function "void drawRAW(char*, int16_t, int16_t, int16_t, int16_t)":

C:\Users\ADMIRAL\Videos\arduino\Libraries\Adafruit_ILI9341_AS\examples\ILI9341_draw_bitmap_v2\ILI9341_draw_bitmap_v2.ino:377:40: warning: converting to non-pointer type "int" from NULL [-Wconversion-null]

C:\Users\ADMIRAL\Videos\arduino\Libraries\Adafruit_ILI9341_AS\examples\ILI9341_draw_bitmap_v2/ILI9341_draw_bitmap_v2.ino:355: undefined reference to `FatFile::close()"

C:\Users\ADMIRAL\Videos\arduino\Libraries\Adafruit_ILI9341_AS\examples\ILI9341_draw_bitmap_v2/ILI9341_draw_bitmap_v2.ino:338: undefined reference to `FatFile::read(void*, unsigned int)"

The Shield TFT is usually supplied with an SD card module to store data or images. Touchscreen LCDs to display images and create graphical user interfaces. In this tutorial, we use the Kuman TFT 2.8″ shield (very similar to the 3.5″ shield) and we will see how to interface with the microSD card.

The shield is placed directly on an Arduino UNO or Mega board. The shield uses almost all the pins of the Arduino UNO. Make sure you don’t use the same ones for other modules. The SD card module of the TFT shield uses the SPI bus and selector pin 10.

The main interest of the MicroSD module on the TFT shield is to be able to store images in order to display them on the screen. If you don’t have a bitmap image at hand, you can download the one we use in this example.

We will create a button for each file and with the help of the previous function we will display the images contained in the SD card when we press the corresponding button.

Once the code is uploaded, a menu will appear with a button for each file contained on the SD card. If you press a button, the corresponding bitmap image will be displayed on the screen. If you press the screen again you will return to the main menu.

A 2.4” TFT LCD module consists of a bright backlight (4 white LEDs) and a colourful 240X320 pixels display. It also features individual RGB pixel control giving a much better resolution than the black and white displays. A resistive touch screen comes pre-installed with the module as a bonus and hence you can easily detect your finger presses anywhere on the screen.

This mode is generally used when speed is not the priority. It is very easy to port to different microcontrollers. In SPI mode, microSD card socket can be used on the same SPI bus. It sends one bit at a time, hence it is slower than the 8-bit mode which sends all the bits in parallel.

The TFT comes with an auto-reset circuit which gets active on every breakout. However, a user can reset the module using this pin also, in case setup is not resetting clean.

The TFT comes with an auto-reset circuit which gets active on every breakout. However, a user can reset the module using this pin also, in case setup is not resetting clean.

Resistive Touch Pins – Y+, X+, Y-, and X- are the 4 resistive touch pins which require analog pins to read and determine touch pins. Their overlay is fixed at the top of the module which makes them electrically separate from the TFT. They can be used is 8-bit as well as SPI mode.

The 2.4” TFT LCD module supports many modes. However, two of them are very popular among users – “SPI mode” and “8-bit mode”. The display contains pins on both sides required for a mode and a user can switch easily between them by simply rewiring the display. It should be noted that only one mode can be used at a time.

The 74LVX245 chip is responsible for interfacing the display with MCU/MPU; it provides fast level shifting so that the user can work on both the logic levels. All the pins are 3.5V logic level compatible. However, if there is an output, the level goes at 3.3V.

A 2.4” TFT module has a very flexible usage. It is compatible with all your DIY projects where you want to add a bright, colourful, and touchscreen enabled display.