Drawing Bitmaps

There is a built in microSD card slot into the breakout, and we can use that to load bitmap images! You will need a microSD card formatted FAT16 or FAT32 (they almost always are by default).

It's really easy to draw bitmaps. We have a library for it, Adafruit_ImageReader, which can be installed through the Arduino Library Manager (Sketch→Include Library→Manage Libraries…). Enter “imageread” in the search field and the library is easy to spot:

Let's start by downloading this image of a lily:

Copy lily128.bmp into the base directory of a microSD card and insert it into the microSD socket in the breakout.

Two more wires are required to interface with the onboard SD card.

You'll need to connect up the MISO pin to the SPI MISO line on your microcontroller. On Arduino Uno/Duemilanove/328-based, thats Digital 12. On Mega's, its Digital 50 and on Leonardo/Due its ICSP-1 (See SPI Connections for more details)

Also, CCS pin to Digital 4 on your Arduino as well. You can change this pin later, but stick with this for now.

You may want to try the SD library examples before continuing, especially one that lists all the files on the SD card

Open the File→examples→Adafruit ImageReader Library→BreakoutST7735 - 128x128 example

In the example, find the following section of code:

Download: file
// Load full-screen BMP file 'rgbwheel.bmp' at position (0,0) (top left).
// Notice the 'reader' object performs this, with 'tft' as an argument.
Serial.print(F("Loading rgbwheel.bmp to screen..."));
stat = reader.drawBMP("/rgbwheel.bmp", tft, 0, 0);
reader.printStatus(stat);   // How'd we do?

On the line with reader.drawBMP() change "/rgbwheel.bmp" to "/lily128.bmp".

After that, upload it to your Arduino. When the Arduino restarts, you should see the flower as below!

To make new bitmaps, make sure they are less than 128 by 128 pixels and save them in 24-bit BMP format! They must be in 24-bit format, even if they are not 24-bit color as that is the easiest format for the Arduino. You can rotate images using the setRotation() procedure

You can draw as many images as you want - dont forget the names must be less than 8 characters long. Just copy the BMP drawing routines below loop() and call

bmpDraw(bmpfilename, x, y);

For each bitmap. They can be smaller than 128x128 and placed in any location on the screen.

This guide was first published on Sep 05, 2014. It was last updated on Sep 05, 2014. This page (Drawing Bitmaps) was last updated on Oct 13, 2019.