/ST7735_TFT_RPI

Library for TFT SPI LCD, ST7735 Driver, Raspberry Pi C++.

Primary LanguageC++GNU General Public License v3.0GPL-3.0

Donate

ig

Table of contents

Overview

  • Name: ST7735_TFT_RPI
  • Description:
  1. C++ Library for a TFT SPI LCD, ST7735 Driver
  2. Dynamic install-able Raspberry Pi C++ library.
  3. Inverse colour, rotate, sleep, idle & vertical scroll modes supported.
  4. 8 fonts
  5. Graphics + print class included.
  6. 24 bit colour , 16 bit color & bi-color Bitmaps supported.
  7. Hardware and Software SPI
  8. Dependency: bcm2835 Library
  • Author: Gavin Lyons
  • Port of my PIC library at github link.
  • Created: May 2021
  • Developed on
    1. Raspberry PI 3 model b
    2. C++ g++ (Raspbian 8.3.0-6+rpi1) 8.3.0
    3. Raspbian 10 Buster OS , armv7l Linux 5.10.63-v7
    4. bcm2835 Library 1.68

Installation

  1. Make sure SPI bus is enabled on your raspberry PI

  2. Install the dependency bcm2835 Library if not installed (at time of writing latest version is 1.68.)

  3. Download the STT735_TFT_RPI library

    • Open a Terminal in a folder where you want to download,build & test library
    • Run following command to download from github.
curl -sL https://codeload.github.com/amrka/ST7735_TFT_RPI/tar.gz/refs/tags/1.6 | tar xz
  1. Install library. Run "make" to run the makefile to install library, it will be installed to usr/lib and usr/include
cd ST7735_TFT_RPI-1.6
sudo make

Test

  1. Next step is to test TFT and installed library with the included main.cpp test example file. Wire up your TFT. Next enter the example folder and run the makefile in THAT folder, This second makefile builds the examples file using the just installed library, and creates a test exe file in "bin". Make run will use "sudo" as the bcm2835 requires root permissions by default see here for details you should now see the test routines in that file running on the display. The example file is setup by default for a 128x128 red tab TFT.
cd example/
make
make run
  1. There are three examples files. The default example file is Tests. To decide which one the makefile(In examples folder) builds simply edit "SRC" variable at top of the makefile. In the "User SRC directory Option Section" at top of file. Pick an example "SRC" directory path and ONE ONLY.
# example file name Desc
1 src/Tests Tests text , fonts, bitmap ,functions
2 src/Hello_world basic use case
3 src/Frame_rate_test FPS speed testing

Software

API

The API (application programming interface) documentation is at link hosted on github pages and generated by Doxygen.

URL

USER OPTIONS

In the example files. There are 3 sections in "Setup()" function where user can make adjustments to select for SPI type used, PCB type used and screen size.

  1. USER OPTION 1 GPIO/SPI TYPE
  2. USER OPTION 2 SCREEN SECTION
  3. USER OPTION 3 PCB_TYPE, SPI SPEED , SPI_CE_PIN

USER OPTION 1 SPI TYPE / GPIO

This library supports both Hardware SPI and software SPI. The parameters set for TFTSetupGPIO define which is used, by default its Hardware. to switch between the two: set SCLK, SDIN and CS to -1 for HW SPI set them to valid GPIO numbers for SW SPI. HW SPI is far faster and more reliable than SW SPI If user is having reliability issues with SW SPI in some setups. The user can adjust the TFT_HIGHFREQ_DELAY setting in ST7735_TFT.h file, this is a microsecond delay in SW SPI loop. It is set to 0 by default, Increasing it will slow down SW SPI further.

USER OPTION 2 Screen size + Offsets

User can adjust screen pixel height, screen pixel width and x & y screen offsets. These offsets can be used in the event of screen damage or manufacturing errors around edge such as cropped data or defective pixels. The function TFTInitScreenSize sets them.

USER OPTION 3 PCB Version, SPI SPEED , SPI_CE_PIN

TFTInitPCBType method

  1. Param1 PCB_TYPE

In the main.cpp in USER OPTION 3 PCB_TYPE select your display type. By passing an enum type to function TFTInitPCBType. Default is "TFT_ST7735R_Red". There are 4 types of the ST7735 TFT display supported. If your display works but RGB colors are inverted you may have chosen wrong display type.

Number Description Enum label Tested
1 ST7735B controller TFT_ST7735B n/a
2 ST7735R Green Tab TFT_ST7735R_Green n/a
3 ST7735R Red Tab TFT_ST7735R_Red RED PCB v1.1, 1.44, 128x128 pixels
4 ST7735S Black Tab TFT_ST7735S_Black RED PCB v1.2, 1.8, 128 x 160 pixels
  1. Param2 SPI_Speed (HW SPI Only)

Here the user can pass the SPI Bus freq in Hertz, Maximum 125 Mhz , Minimum 30Khz, The default in file is 8Mhz If you set to 0 .Speed is set to bcm2835 constant BCM2835_SPI_CLOCK_DIVIDER_32. If using SW spi, ignore.

  1. Param3 SPI_CE_PIN (HW SPI Only)

Which Chip enable pin to use two choices. If using SW spi, ignore. * SPICE0 = 0 * SPICE1 = 1

Files

In example folder: The Main.cpp file contains tests showing library functions. A bitmap data file contains data for bi-color bitmaps and icons tests. The color bitmaps used in testing are in bitmap folder, 3 16-bit and 3 24-bit images.

There are two makefiles

1. At root directory builds and installs library at a system level.
2. Example directory builds example file + installed library to an executable.

Fonts

8 fonts available :

num name size xbyy ASCII range
1 Default 5x8 Full Extended ASCII 0x00 - 0xFF
2 Thick 7x8 ASCII 0x20 - 0x5A , no lowercase letters
3 Seven segment 4x8 ASCII 0x20 - 0x7A
4 Wide 8x8 ASCII 0x20 - 0x5A , no lowercase letters
5 Tiny 3x8 ASCII 0x20 - 0x7A
6 Homespun 7x8 ASCII 0x20 - 0x7A
7 Big Nums 16x32 ASCII 0x2E-0x3A , Numbers + : . only
8 Med Nums 16x16 ASCII 0x2E-0x3A , Numbers + : . only

The fonts 1-6 are byte high(at text size 1) scale-able fonts, The large numerical Fonts, 7 & 8 cannot be scaled.

Bitmap

There are four functions to support drawing bitmaps

Function Name Colour support Pixel size Note
TFTdrawIcon bi-colour 8 x(0-127) Data vertically addressed
TFTdrawBitmap bi-colour 2048 bytes max Data horizontally addressed
TFTdrawBitmap16 16 bit color 565 BMP files 32K max ------
TFTdrawBitmap24 24 bit color BMP files 48K max Converted by software to 16-bit color
  1. Bitmap size in kiloBytes = (screenWidth * screenHeight * bitsPerPixel)/(1024 * 8)
  2. Pixel size column assumes 128 by 128 screen.

Hardware

Connections as setup in main.cpp test file.

TFT PinNum Pindesc RPI HW SPI RPI SW SPI
1 LED VCC VCC
2 SCLK SPI_CLK GPIO5
3 SDA SPI_MOSI GPIO6
4 A0/DC GPIO24 GPIO24
5 RESET GPI025 GPIO25
6 SS/CS SPI_CE0 GPIO8
7 GND GND GND
8 VCC VCC VCC
  1. Connect LED backlight pin 1 thru a 150R/220R ohm resistor to 3.3/5V VCC.
  2. This is a 3.3V logic device do NOT connect the I/O logic lines to 5V logic device.
  3. You can connect VCC to 5V if there is a 3.3 volt regulator on back of TFT module.
  4. Pick any GPIO you want for SW SPI for HW SPI: reset and DC lines are flexible.
  5. User can select SPI_CE0 or SPI_CE1 for HW SPI wiring
  6. Backlight control is left to user.

Output

Output of some of the test routine's. Left to right, top to bottom.

  1. Different defined colors at default font size 1. Full 16 bit colour 565 available
  2. Different sizes of default font. Size 2 3 4 & 5 shown.
  3. Different Fonts at font size 2, fonts 1-5. Are these fonts are scale-able, font 6 not shown.
  4. Shapes
  5. More Shapes!
  6. Bitmap (bi-color) A background and a foreground.
  7. Clock Demo showing icons, small bitmaps and font 7 "BigNums"
  8. 24-bit color bitmap test image
  9. 16-bit color bitmap test image

pic pic1