- 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 supported.
- Hardware and Software SPI
- Dependency: bcm2835 Library
- 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 SPEED , SPI_CE_PIN
USER OPTION 1 SPI TYPE / GPIO
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. HW SPI is far faster and more reliable than SW SPI
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 InitScreenSize sets them.
USER OPTION 3 SPI SPEED , SPI_CE_PIN
InitSPI function is overloaded(2 off, one for HW SPI the other for SW SPI).
Param 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 Although it is possible to select high speeds for the SPI interface, up to 125MHz, Don't expect any speed faster than 32MHz to work reliably. If you set to 0 .Speed is set to bcm2835 constant BCM2835_SPI_CLOCK_DIVIDER_32.
Param SPI_CE_PIN (HW SPI Only)
Which Chip enable pin to use two choices. * SPICE0 = 0 * SPICE1 = 1
Param SPI_CommDelay (SW SPI Only)
The user can adjust If user is 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 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 5 24-bit images.
| # | example file name | Desc |
|---|---|---|
| 1 | Hello_world | Basic use case |
| 2 | Text_Graphic_Functions | Tests text,graphics & function testing |
| 3 | Bitmap_Tests | bitmap |
| 4 | Frame_rate_test_bmp | Frame rate per second (FPS) bitmaps |
Tested and developed on:
- Size 1.69" 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 | GPIO8 |
| 3 | DC | GPIO24 | GPIO24 |
| 4 | RESET | GPI025 | GPIO25 |
| 5 | SDA | SPI_MOSI | GPIO6 |
| 6 | SCLK | SPI_CLK | GPIO5 |
| 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.
When using hardware SPI for multiple devices on the bus. If the devices require different SPI settings (speed of bus, bit order , chip enable pins , SPI data mode). The user must call function TFTSPIHWSettings() before each block of SPI transactions for display in order to refresh the SPI hardware settings for that device. See github issue #1.
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.