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GC9A01A Readme

Table of contents

Overview

  • Name: GC9A01A
  • Description:
  1. C++ Library for a TFT SPI LCD, GC9A01A Driver
  2. Dynamic install-able Linux C++ library.
  3. Power modes, Invert , Scroll, Rotate, Bitmaps supported.
  4. Graphics + print class included.
  5. 24 bit colour , 16 bit color, bi-color Bitmaps & sprites supported.
  6. Hardware and Software SPI
  7. Dependency: lgpio Library
  8. 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.
  9. Make sure SPI is enabled in your computers configuration.
  10. Tested on 240x240 pixel round display.

Software

User options

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.

  1. USER OPTION 1 GPIO/SPI TYPE
  2. USER OPTION 2 SCREEN SECTION
  3. USER OPTION 3 SPI SETTINGS

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.

USER OPTION 2 Screen size

User can adjust screen pixel height, screen pixel width. The function InitScreenSize sets them.

USER OPTION 3 SPI Settings

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.

File system

In example sub folders: 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. Hello world can be setup for software or hardware SPI by changing "HardwareSPI" at top of file.

# example sub folder name Description
1 hello_world Basic use case
2 tests Tests bitmap, text,graphics & function testing
3 demos Various demos

Bitmap

Bitmap Documentation

Color codes

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

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.

Hardware

pic

Connections as setup in main.cpp test file. Connections as setup in main.cpp test file.

TFT PinNum Pindesc RPI HW SPI RPI SW SPI
1 LED VCC VCC
2 CS SPI_CE0 GPI21
3 DC GPIO24 GPIO24
4 RESET GPI025 GPIO25
5 SDA SPI_MOSI GPIO16
6 SCLK SPI_CLK GPIO20
7 VCC VCC VCC
8 GND GND GND
  1. This is a 3.3V logic device do NOT connect the I/O logic lines to 5V logic device.
  2. SW SPI pick any GPIO you like , HW SPI CEX, SCLK and SDA will be tied to SPI interface.
  3. Backlight on/off control is left to user.

Output

Demo pic

Notes

Error 99

Error 99 Documentation