Matrix - 2'8 SPI Key TFT

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1 Introduction

• Matrix-2'8_SPI_Key_TFT模块是一款2.8英寸的TFT 触摸LCD，模块采用ST7789S驱动IC和XPT2046电阻式触摸IC，屏幕分辨率为320*240，采用SPI控制接口，模块还包含3个独立按键，可根据需要自定义功能。
• 详细规格如下所示：

LCD尺寸	2.8寸
显示区域	57.6mm*43.2mm
驱动IC	ST7789S
分辨率	320*240（RGB）
接口方式	SPI
工作电压	5V
背光电压	5V
触摸屏类型	电阻式，钢化玻璃触摸屏

模块上电默认打开背光，可通过置低LED_EN引脚关闭背光。如果需要关闭上电打开背光，只需要拿到电路板上的R12电阻，再通过置高LED_EN引脚打开背光；

2 Features

• PCB dimension(mm):

• Pin Description:

Pin	Description	Pin	Description
1	VDD_3.3V	2	VDD_5V
3	NC	4	VDD_5V
5	NC	6	GND
7	LCD_RESET	8	NC
9	GND	10	NC
11	LED_EN	12	NC
13	KEY_1	14	GND
15	KEY_2	16	KEY_3
17	VDD_3.3V	18	T_IRQ
19	SPI_MOSI	20	GND
21	SPI_MISO	22	LCD_D/C
23	SPI_CLK	24	LCD_CS
25	GND	26	T_CS

4 Connect to NanoPi 2

4.1 Hardware Connection

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

Connection Details:

Matrix-2'8_SPI_Key_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

4.2 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

4.3 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.

4.4 Test LCD Display

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

4.5 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.

5 Connect to NanoPi

5.1 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

5.2 Hardware Connection

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

Connection Details:

Matrix-2'8 SPI_TFT	NanoPi

5.3 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 st7789s chip and the "matrix_ads7846" module is the driver for the xpt2046 chip.

5.4 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.

5.5 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.

10 Update Log

10.1 Feb-24-2016

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