NanoPi NEO Air使用十二：使用自带的fbtft驱动点亮SPI接口TFT屏幕，ST7789V
上节自己编写spi驱动来点亮spi接口的小屏幕，其实Linux内核里已经提供spi接口小屏的设备驱动，即内核中已经自带了此类驱动，名字为fbtft。本节就来使用它。
引脚
240x240分辨率，1.3寸，主控为ST7789VW。
与开发板的引脚连接确定如下：
| 功能 | IO |
|---|---|
| GND | Pin6 |
| 5V | Pin2 |
| LCD_RESET | Pin7-PG11 |
| LCD_DC | Pin22-PA1 |
| SPICLK | Pin23-PC2 |
| SPIMOSI | Pin19-PC0 |
从开发板的引脚图发现，开发板使用的SPI0。
修改设备树
打开/home/ql/linux/H3/linux/arch/arm/boot/dts/sun8i-h3-nanopi.dtsi，找到spi0节点，修改为如下：
&spi0 {
/* needed to avoid dtc warning */
#address-cells = <1>;
#size-cells = <0>;
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&spi0_pins &spi0_cs_pins>;
cs-gpios = <&pio 2 3 GPIO_ACTIVE_HIGH>, <&pio 0 6 GPIO_ACTIVE_HIGH>; /*SPI-CS:PC3 and PA6*/
pitft: pitft@0{
compatible = "sitronix,st7789vw";
reg = <0>;
status = "okay";
spi-max-frequency = <50000000>;
rotate = <0>;
fps = <33>;
buswidth = <8>;
dc-gpios = <&pio 0 1 GPIO_ACTIVE_HIGH>; /* PA1 */
reset-gpios = <&pio 6 11 GPIO_ACTIVE_HIGH>; /* PG11 */
led-gpios = <&pio 0 0 GPIO_ACTIVE_LOW>; /* PA0 */
debug = <0x0>;
};
};
&pio {
leds_npi: led_pins {
pins = "PA10";
function = "gpio_out";
};
pinctrl_testTFTRes: testTFTRes_pins {
pins = "PG11";
function = "gpio_out";
};
pinctrl_testTFTDc: testTFTDc_pins {
pins = "PA1";
function = "gpio_out";
};
pinctrl_testTFTBk: testTFTBk_pins {
pins = "PA0";
function = "gpio_out";
};
spi0_cs_pins: spi0_cs_pins {
pins = "PC3", "PA6";
function = "gpio_out";
};
};
关闭HDMI，否则设备默认HDMI输出，tft黑屏
&hdmi {
//status = "okay";
status = "disable";
};
&hdmi_out {
hdmi_out_con: endpoint {
remote-endpoint = <&hdmi_con_in>;
};
};
&sound_hdmi {
//status = "okay";
status = "disable";
};
修改驱动文件
打开/home/ql/linux/H3/linux/drivers/staging/fbtft/路径，看下有没有fb_st7789vw.c文件，如果有下面的步骤就可以忽略了。
如果没有，那么新建一个fb_st7789vw.c文件，把下面内容复制进去，保存。
/*
* FB driver for the ST7789V LCD Controller
*
* Copyright (C) 2015 Dennis Menschel
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
#include 在Makefile中添加obj-$(CONFIG_FB_TFT_ST7789VW) += fb_st7789vw.o
在Kconfig中添加
config FB_TFT_ST7789VW
tristate "FB driver for the ST7789VW LCD Controller"
depends on FB_TFT
help
This enables generic framebuffer support for the Sitronix ST7789VW
display controller. The controller is intended for small color
displays with a resolution of up to 240x240 pixels.
Say Y if you have such a display that utilizes this controller.
编译
到menuconfig中使能此驱动
make menuconfig ARCH=arm CROSS_COMPILE=arm-linux-
Device Drivers --->
[*] Staging drivers --->
<*> Support for small TFT LCD display modules --->
<*> FB driver for the ST7789VW LCD Controller
# 编译内核、设备树
make zImage dtbs ARCH=arm CROSS_COMPILE=arm-linux-
# 网络更新内核
scp arch/arm/boot/zImage [email protected]:/boot
# 网络更新设备树
scp arch/arm/boot/dts/sun8i-h3-nanopi-neo-air.dtb [email protected]:/boot
实际效果
命令行
上面的步骤做完了，重启就会有如下画面
我们一直使用SecureCRT作为Linux开发板终端，开发板通过串口和SecureCRT进行通信。现在我们已经驱动起来 LCD 了，所以可以设置 LCD 作为终端，也就是开发板使用自己的显示设备作为自己的终端，然后接上键盘就可以直接在开发板上敲命令了。
我们就拥有了两套终端，一个是基于串口的 SecureCRT，一个就是我们开发板的 LCD屏幕，但是为了方便调试，我们以后还是以 SecureCRT 为主。我们可以通过下面这一行命令向LCD 屏幕输出“hello linux！”
echo hello linux > /dev/tty1
播放视频
sudo apt install mplayer # 安装mplayer
mplayer 1.mp4 -vo fbdev
运行QT
下面的指令都要切换root执行
apt-get update && apt-get install git
git clone https://github.com/friendlyarm/matrix.git
cd matrix/demo/nanopi-status
./build.sh
./run.sh /dev/fb_st7789vw
轻量级界面
sudo apt install xfce4
startx
让屏幕旋转180度
如果要让屏幕旋转180度，首先修改设备树：
&spi0 {
/* needed to avoid dtc warning */
#address-cells = <1>;
#size-cells = <0>;
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&spi0_pins &spi0_cs_pins>;
cs-gpios = <&pio 2 3 GPIO_ACTIVE_HIGH>, <&pio 0 6 GPIO_ACTIVE_HIGH>; /*SPI-CS:PC3 and PA6*/
pitft: pitft@0{
compatible = "sitronix,st7789vw";
reg = <0>;
status = "okay";
spi-max-frequency = <50000000>;
rotate = <180>;
fps = <33>;
buswidth = <8>;
dc-gpios = <&pio 0 1 GPIO_ACTIVE_HIGH>; /* PA1 */
reset-gpios = <&pio 6 11 GPIO_ACTIVE_HIGH>; /* PG11 */
led-gpios = <&pio 0 0 GPIO_ACTIVE_LOW>; /* PA0 */
debug = <0x0>;
};
};
drivers/staging/fbtft/fb_st7789vw.c驱动中的set_var函数会生效，修改相应寄存器
如果这个时候直接测试，会发现屏幕有偏移，屏幕只有上部分有显示。
因此还需要修改下面函数来纠正：
static void set_addr_win(struct fbtft_par *par, int xs, int ys, int xe, int ye)
{
switch(par->info->var.rotate)
{
case 0: xs+=0;xe+=0;ys+=0;ye+=0;
break;
// case 90: xs+=0;xe+=0;ys+=53;ye+=53;
// break;
case 180: xs+=0;xe+=0;ys+=80;ye+=80;
break;
// case 270: xs+=0;xe+=0;ys+=53;ye+=53;
// break;
default :
break;
}
write_reg(par, MIPI_DCS_SET_COLUMN_ADDRESS,
xs >> 8, xs & 0xFF, xe >> 8, xe & 0xFF);
write_reg(par, MIPI_DCS_SET_PAGE_ADDRESS,
ys >> 8, ys & 0xFF, ye >> 8, ye & 0xFF);
write_reg(par, MIPI_DCS_WRITE_MEMORY_START);
}
旋转90度和270度不知道需不需要纠偏，等以后用到再说。