“This is a graphics library for the family of small colour TFT displays based on the ST7735 and ST7789 driver chips. These are really nice displays; bright, colourful, available in a variety of useful sizes, and available at low cost from suppliers like Adafruit, AliExpress, or Banggood
This library allows you to plot points, draw lines, draw filled rectangles, and plot text with an optional scale factor. I’ve included a demo histogram-plotting program that adjusts itself to fit each of the displays I’ve supported.
Unlike most other TFT display libraries this one doesn’t require a memory buffer, allowing it to be run on any processor down to an ATtiny85. The displays require four pins to drive the display, leaving one pin free on an ATtiny85 to interface to another device, such as a temperature sensor. If you need more pins choose a larger chip, such as the ATtiny84; see Using the library with other AVR chips at the end of the article for information about how to convert the code for different chips.
I started developing this library for another project that I hope to write about at a later date; in the meantime I thought it would be useful to write it up as a stand-alone article.
I’ve published a library for a colour OLED display in a previous article: Colour Graphics Library. The main difference between the colour TFT displays and the colour OLED displays is that the TFT displays are not self-illuminating, and so need a backlight; they therefore have a slightly higher power consumption. However, they are exceedingly cheap, and they are available in larger sizes than the colour OLED displays.
I wrote an initial version of this library in uLisp, my Lisp interpreter for microcontrollers, which made it easy to experiment with different approaches. I then converted it to C to run on an ATtiny85. I can publish the uLisp version if anyone’s interested.”