- Name: ST7789_TFT
- Description:
- C++ Library for a TFT SPI LCD, ST7789 Driver
- Dynamic install-able Raspberry Pi C++ library.
- Inverse colour, rotate, sleep modes supported.
- Graphics + print class included.
- 24 bit colour , 16 bit color, bi-color Bitmaps & sprites supported.
- Hardware and Software SPI
- Dependency: lgpio Library
- NB The Spidev buffer size setting must be larger than biggest buffer the code will attempt to write If not you will get 'Error 99'. See Notes section for more details.
- Make sure SPI is enabled in your computers configuration.
- Author: Gavin Lyons
In the example files. There are 3 sections in "Setup()" function where user can make adjustments to select for SPI type used, and screen size.
- USER OPTION 1 GPIO/SPI TYPE
- USER OPTION 2 SCREEN SECTION
- USER OPTION 3 SPI SETTINGS
This library supports both Hardware SPI and software SPI. The SetupGPIO function is overloaded(2 off one for HW SPI the other for SW SPI). The parameters set for SetupGPIO define which is used.
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 InitScreenSize sets them.
InitSPI function is overloaded(2 off, one for HW SPI the other for SW SPI).
| parameter | default value | note | SPi type |
|---|---|---|---|
| HWSPI_DEVICE | 0 | A SPI device, >= 0. which SPI interface to use , ls /dev/spi* | Hardware |
| HWSPI_CHANNEL | 0 | A SPI channel, >= 0. Which Chip enable pin to use usually 0 or 1 | Hardware |
| HWSPI_SPEED | 1000000 | The speed of serial communication in bits per second. | Hardware |
| HWSPI_FLAGS | 0 | mode 0 for this device | Hardware |
| GPIO_CHIP_DEVICE | 0 | gpio chip device >= 0, check ls/dev/gpiochip* | both |
| SWSPI_CommDelay | 0 | uS delay for GPIO | software |
The user can adjust if having reliability issues with SW SPI in some setups. This is a microsecond delay in SW SPI GPIO loop. It is set to 0 by default, Increasing it will slow down SW SPI further.
In example folder: the main.cpp files contain 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. Hello world can be setup for software or hardware SPI by changing "HardwareSPI" at top of file.
| # | example file name | Description |
|---|---|---|
| 1 | hello_world | Basic use case |
| 2 | text_graphic_functions | Text,graphics & function testing |
| 3 | bitmap_Tests | bitmap |
| 4 | framerate_test | Frame rate per second (FPS) |
| 5 | demos | Various demos |
For functions that accept a 16 bit color value. There is list of pre-defined colors in the 'colors' folder in doc.
Advanced screen buffer mode. There is advanced buffer mode where the code writes to a global screen buffer instead of the VRAM of display. It is off by default more details at readme, which is in the 'doc' folder at link.
Tested and developed on:
- Size 1.69 inch IPS color TFT LCD
- Resolution: 240 (H) RGB x280 (V)
- Control chip: st7789v2
- Display area 27.972 (H) x 32.634 (V)
- Panel size 30.07 (H) x37.43 (V) x1.56 (d)
- Logic voltage 3.3V
Connections as setup in main.cpp test file.
| TFT PinNum | Pindesc | RPI HW SPI | RPI SW SPI |
|---|---|---|---|
| 1 | LED | VCC | VCC |
| 2 | SS/CS | SPI_CE0 | GPIO21 |
| 3 | DC | GPIO24 | GPIO24 |
| 4 | RESET | GPI025 | GPIO25 |
| 5 | SDA | SPI_MOSI | GPIO5 |
| 6 | SCLK | SPI_CLK | GPIO6 |
| 7 | VCC | VCC | VCC |
| 8 | GND | GND | GND |
- Connect LED backlight pin 1 thru a resistor to VCC.
- This is a 3.3V logic device do NOT connect the I/O logic lines to 5V logic device.
- Pick any GPIO you want for SW SPI, for HW SPI: reset and DC lines are flexible.
- User can select SPI_CE0 or SPI_CE1 for HW SPI
- Backlight control is left to user.
The display initialisation requires an offset calculation which differs for different size and resolution displays. This is in the code(Function AdjustWidthHeight()) but the many different size displays are not available for testing or dealt with. If using a display other than 240x320(the default and size of ST7789 VRAM) and if user finds they cannot address all screen or their data is offset. Try Setting the pixel width and height of your screen to 240X320 and do not write as much as possible to the part of the Video RAM you cannot see. For example if you have a 240X280 display in 0 degree rotation
- Set pixel Width = 240 and pixel height = 320
- Do not write to the missing 40 pixels in the Y-axis, you still can but it is inefficient.