Matrix - 2'8 SPI TFT

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1 Introduction

  • The Matrix - 2'8 SPI TFT module is a 2.8" TFT LCD with resistive touch. It uses the ST7789S IC and the XPT2046 resistive IC. The LCD's resolution is 320 * 240 and communicates via SPI.
  • Here is the spec:
LCD Dimension 2.8"
Display Area 57.6mm * 43.2mm
Driver IC ST7789S
Resolution 320 * 240(RGB)
Interface SPI
Supply Voltage 5V
Backlight Voltage 5V
Touch Resistive, Tempered glass LCD

2 Features

  • PCB dimension(mm):

File:Matrix-SPI TFT PCB.png

  • Pin Description:
Pin Description
GND Ground
5V Supply Voltage 5V
LED_EN Backlight
LCD_RESET Reset
LCD_D/C LCD data/command selection
LCD_CS LCD chip selection
SPICLK SPI clock
SPIMOSI SPI MOSI
SPIMISO SPI MISO
T_CS Touch chip selection
T_IRQ Touch IRQ

3 Basic Device Operation

4 Download Matrix Source Code

All the matrix modules' code samples are open source. They are maintained on GitHub - https://github.com/friendlyarm/matrix.git
Each branch in this hub contains the matrix modules' code samples for a board that the matrix modules can work with。

  • The nanopi branch contains the matrix modules' code samples for the NanoPi
  • The nanopi2 branch contains the matrix modules' code samples for the NanoPi 2
  • the tiny4412 branch contains the matrix modules' code samples for the Tiny4412
  • the raspberrypi branch contains the matrix modules' code samples for the RaspberryPi

Please follow the steps below to get the source code:
Install the git utility on a PC running Ubuntu14.04

$ sudo apt-get install git

Clone the matrix code from GitHub

$ git clone https://github.com/friendlyarm/matrix.git

If this is successful a "matrix" directory will be generated, which will contain all the matrix modules' code samples.

5 Connect to NanoPi 2

5.1 Hardware Connection

Please refer to the following connection diagram to connect the Matrix-2'8 SPI_TFT to the NanoPi 2:
Matrix-2'8_SPI_TFT_nanopi2

Connection Details:

Matrix-2'8_SPI_TFT NanoPi 2
GND Pin6
5V Pin2
LED_EN Pin11
LCD_RESET Pin7
LCD_D/C Pin22
LCD_CS Pin24
SPICLK Pin23
SPIMOSI Pin19
SPIMISO Pin21
T_CS Pin26
T_IRQ Pin18

5.2 Compile Test Program

Please login the matrix hub and enter the nanopi2 branch

$ cd matrix
$ git checkout nanopi2

Compile the Matrix code

$ make CROSS_COMPILE=arm-linux- clean
$ make CROSS_COMPILE=arm-linux-
$ make CROSS_COMPILE=arm-linux- install

Note: please make sure to install the cross compiler "arm-linux-gcc-4.9.3" on your PC, which is used to compile files for the NanoPi 2.
Generated library files are under the "install/lib" directory. The test program is under the "install/usr/bin" directory.
The modules are under the "modules" directory. The driver's source code is in github: https://github.com/friendlyarm/linux-3.4.y.git

5.3 Load Driver

Please insert a TF card which is flashed with Debian to a Linux host and mount its boot and rootfs sections.
We assume the rootfs is mounted to /media/rootfs then please run the following commands to copy the driver, library and test program to the card.

$ cp modules /media/rootfs/ -r
$ cp install/lib/* /media/rootfs/lib/ -d
$ cp install/usr/bin/* /media/rootfs/usr/bin/

Insert this TF card to your NanoPi 2, power on and run the following commands to load the driver

$ cd /modules
$ insmod fbtft_device.ko name=matrix-st7789s gpios=dc:97,reset:60,cs:94
$ insmod matrix_ads7846.ko

"fbtft_device" is the LCD's driver. "matrix_ads7846" is the touch driver. If they are successfully loaded the LCD will be cleared and reset.

5.4 Test LCD Display

Please run the following commands to set the display device to the Matrix-2'8_SPI_TFT:

$ sudo FRAMEBUFFER=/dev/fb-st7789s startx &

"&" schedules the program to run background and you will see the following messages:

Log file: "/var/log/Xorg.2.log"

Here the message shows that the X window's DISPLAY value is 2.

5.5 Calibrate Touch

Please run the following commands to calibrate touch:

$ DISPLAY=:2.0 xinput_calibrator

After you click on the four points highlighted on the LCD you will get calibration done and observe the following messages:

Section "InputClass" 
        Identifier      "calibration" 
        MatchProduct    "ADS7846 Touchscreen" 
        Option  "Calibration"   "196 3825 3887 358" 
        Option  "SwapAxes"      "0" 
EndSection

Save these calibration data to the "/usr/share/X11/xorg.conf.d/99-calibration.conf" file and reboot the system your touch will be ready to go.

6 Connect to NanoPi

6.1 Preparations

Please install a Debian on a NanoPi and an appropriate cross compiler on a PC. Please refer to wiki:NanoPi
Compile a NanoPi kernel. Note: please use the kernel's source code from the nanopi-v4.1.y-matrix branch.

$ git clone https://github.com/friendlyarm/linux-4.x.y.git
$ cd linux-4.x.y
$ git checkout nanopi-v4.1.y-matrix
$ make nanopi_defconfig
$ touch .scmversion
$ make

6.2 Hardware Connection

Please refer to the following connection diagram to connect the Matrix-SPI_TFT to the NanoPi
Matrix-SPI_TFT_nanopi

Connection Details:

Matrix-SPI_TFT NanoPi

6.3 Load Driver

Power on the NanoPi and run the following command in Debian's terminal to load drivers:

$ modprobe fbtft_device name=matrix-spi_tft gpios=dc:161,reset:162,cs:163
$ modprobe matrix_ads7846

The "fbtft_device" module is the driver for the ili9341 chip and the "matrix_ads7846" module is the driver for the xpt2046 chip.

6.4 Install Package

Please run the following commands in Debian's terminal to install "qtembedded" and "matrix-tslib"

$ apt-get update
$ apt-get install qtembedded
$ apt-get install matrix-tslib

The "qtembedded" library is what qt applications rely on and the "matrix-tslib" library is what screen calibration relies on.

6.5 Run Test Program

Start Qt applications

$ . /usr/bin/matrix-setqt4env
$ /usr/local/Trolltech/QtEmbedded-4.8.5-arm/examples/tetrix -qws

The matrix-setqt4env script sets the environmental variables which Qt and tslib rely on. If it is run on a platform for the first time a screen calibration GUI will be launched. Users need to go through a five-point calibration process to calibrate the screen. The tetrix application is a game developed in Qt4.

7 Connect to Tiny4412

8 Connect to RaspberryPi

9 Connect to Arduino

10 Resources

11 Update Log

11.1 Feb-24-2016

  • Added the driver's source code location in Section 5.2

11.2 Feb-25-2016

  • Added details for Sections 1 and 2