This repository contains a fast low level Arduino Uno compatible graphics library for the 160x128 pixel 16-bit color TFT LCD display that uses the ST7735R chip. It was written as a programming exercise after realizing that the built-in "Adafruit" TFT library that Arduino ships with is very slow. I wanted to display some slideshow images on the TFT using an Arduino, but unfortunately the built-in libraries take about 2.9 seconds(!) to draw a single 160x128 image on the screen from the SD card. With this library, it is possible to draw an image in about 188 milliseconds, which is a considerable 15.2x performance increase! The aim of this code is to squeeze every individual clock cycle out of the drawing routines to see how fast it is possible to drive the ST7735R display. If you can improve the code here, please let me know.
This library offers (almost) drop-in replacements for most built-in TFT library methods, and comes with the following functions:
- Draw batches of individual pixels with a sequence of
ST7735R_BeginPixels(),ST7735R_Pixel()andST7735R_EndDraw()functions. - Fill solid rectangles with the
ST7735R_FillRect()function. - Stream rectangles of custom content with a sequence of
ST7735R_BeginRect(),ST7735R_PushPixel()andST7735R_EndDraw()functions. - Draw horizontal lines with the function
ST7735R_HLine()and vertical lines with the functionST7735R_VLine(). - Draw arbitrary sloped lines with the function
ST7735R_Line(). - Draw hollow circles with the function
ST7735R_Circle(). - Draw filled circles with the function
ST7735R_FilledCircle(). - Draw 1-bit monochrome sprites from PROGMEM with the function
ST7735R_DrawMonoSprite(). - Draw text stored in PROGMEM with the function
ST7735R_DrawText(). One font file"monaco_font.h"is provided, create more with thettffont_to_cppheader.pytool. - Draw 24-bit bottom-up .bmp images with the functions
LoadBMPImage(),SDCard_GetFileStartingBlock()andST7735R_DrawBMP(). (requires hacking of the built-in SD card library to enable raw FAT32 block streaming). - Draw pre-prepared raw 16-bit images (files formatted with suffix .565) with the functions
SDCard_GetFileStartingBlock()andST7735R_Draw565(). (requires hacking of the built-in SD card library to enable raw FAT32 block streaming). Use the python toolimage_to_rgb565.pyto convert images to this format.
The library has only been used on an Arduino Uno with 8MHz hardware SPI mode, and contains several assumptions that might not hold when transferring the configuration to other setups. Don't use blindly without understanding the internals of the code!
- The display: http://www.arduino.cc/en/Guide/TFT (bought from http://www.verkkokauppa.com/fi/product/30873/dsgrv/Arduino-1-77-TFT-LCD-Screen-naytto-Arduino-kehitysalustoille)
- Wiring instructions at http://www.arduino.cc/en/Guide/TFTtoBoards
- Data sheet at http://www.adafruit.com/datasheets/ST7735R_V0.2.pdf
- Atmel AVR 8 bit instruction set documentation: http://www.atmel.com/images/doc0856.pdf
- Requires manual pin to port+bit mapping configuration. This is useful: http://pighixxx.com/unov3pdf.pdf
Unless otherwise stated in individual files, all code is released to public domain. Do whatever you wish with it. This repository is a result of some recreational hacking activity, rather than a mission to build a stable and maintained library, so expect the maturity to be as such.
The files Testx_yyyyy.h implement different test rendering patterns for the library. To run one of these tests, open the file ST7735R.ino in the Arduino IDE, and uncomment the appropriate #include "Testx_yyyyy.h" lines to build that test. Configure the file accordingly. In order for the default configuration to work, you must run on Arduino Uno and have the pins connected according to the order recommended here: http://www.arduino.cc/en/Guide/TFTtoBoards . Otherwise edit the #defines at the top of the files ST7735R_TFT.h and SDCardBlockRead.h.
This test measures rectangle filling performance, and compares the Arduino TFT::background() method to its replacement function ST7735R_FillRect() in this library.
This test measures the performance of drawing multiple small rectangles, and compares the Arduino TFT::point() method to ST7735R_FillRect() in this library.
This test is a comparison of the Arduino TFT::text() function against the ST7735R_DrawText() function in this library.
This test measures the performance of drawing individual pixels with TFT::point() against the ST7735R_Pixel() function in this library. In this library, individual pixel rendering is batched, and must be enclosed between a block of calls to the functions ST7735R_BeginPixels() and ST7735R_EndDraw().
This test draws arbitrarily slanted lines using either the Arduino function TFT::line(), or the function ST7735R_Line() in this library.
In this sample, a slideshow of full screen .bmp images are rendered with the functions TFT::loadImage + TFT::image, or with the functions LoadBMPImage(SDCard_GetFileStartingBlock(filename)) and ST7735R_DrawBMP().
This test demonstrates how a custom prepared file format can be used to accelerate imare rendering even further. The functions SDCard_GetFileStartingBlock() and ST7735R_Draw565() are used here.
This sample code draws small polyline segments and compares the tradeoff of rendering individual points versus lines.
This test demonstrates the rendering of hollow circles, either using the built-in TFT::circle() function (with the noFill option), or the function ST7735R_Circle() found in this library.
This test demonstrates the rendering of solid filled circles, either using the built-in TFT::circle() function (with the noStroke option), or the function ST7735R_FilledCircle() from in this library.
Toggle the #define USE_ARDUINO_TFT in ST7735R.ino to compare performance between the built-in Arduino "Adafruit" TFT library and this library. Each test measures the total time to render per frame in microseconds. That gives several data points to compare the performance of this library against the built-in library.
| Test | Adafruit | This library | Relative |
|---|---|---|---|
| Test1_FillScreen | 105752 µsecs | 54072 µsecs | -48.9% |
| Test2_Blocks | 524184 µsecs | 20480 µsecs | -96.0% |
| Test3_WanderingText | 218328 µsecs | 28556 µsecs | -86.9% |
| Test4_Starfield | 68302 µsecs | 25670 µsecs | -62.4% |
| Test5_Lines | 592560 µsecs | 61460 µsecs | -89.6% |
| Test6_DrawBMP | 2858852 µsecs | 318028 µsecs | -88.9% |
| Test7_Draw565 | N/A | 187820 µsecs | - |
| Test8_HilbertCurve | 576948 µsecs | 324492 µsecs | -43.8% |
| Test9_HypnoCircle | 915260 µsecs | 111356 µsecs | -87.8% |
| Test10_FilledCircle | 2082480 µsecs | 933720 µsecs | -55.2% |
Overall the data shows that one can expect a performance increase from 2x to 10x by bypassing the built-in TFT library.