在Raspberry Pi Zero W中配置TFT LCD Framebuffer驱动

TFT LCD Framebuffer驱动配置

本文将以ILI9341 LCD为例，将详细介绍如何配置TFT LCD的Framebuffer驱动。

1、硬件准备

• Raspberry Pi Zero W开发板一个（镜像Linux内核版本为5.18.84+）
• TFT LCD 模块一个（ILI9341驱动IC）
• 连接线
• 数据线
• 面包板

TFT LCD与Raspberry Pi Zero W接线如下：

序号	TFT LCD	Raspberry PI
1	VCC	3.3V或5V
2	GND	GND
3	SCK	GPIO 11 SCLK （SPI0）
4	SDA	GPIO10 MOSI （SPI0）
5	RST	GPIO 6
6	DC	GPIO 5
7	CS	GPIO8 Chip-Enable-CE0（SPI0）

Raspberry PI Zero W的引脚如下：

2、软件配置

2.1 启用SPI驱动

在命令行中输入：

sudo raspi-config

选择3 Interface Options进入接口驱动配置页面：

选择I4 SPI Enable/disable automatic loading of SPI kernel module开启或关闭SPI驱动。

另外，如果不想在命令中配置，也可以在图形界面中配置。还可以修改/boot/config.txt文件：

将 #符号删除即可启用spi。

2.2 TFT LCD设备驱动树配置

下面将创建自定义的DTS文件。下面将创建一个名称为ili9341.dts的文件。其内容如下：

/dts-v1/;
/plugin/;

/ {
	compatible = "brcm,bcm2835";

	// Enable the SPI controller
	fragment@0 {
		target = <&spi0>;
		__overlay__ {
			status = "okay";
		};
	};

	// Enabling the SPI controller also enables spidev on cs0, so we have disable it
	fragment@1 {
		target = <&spidev0>;
		__overlay__ {
			status = "disabled";
		};
	};

	fragment@2 {
		target = <&spi0>;
		__overlay__ {
			/* needed to avoid dtc warning */
			#address-cells = <1>;
			#size-cells = <0>;

			display: display@0{
				// MIPI DBI compatible driver
				// This driver is used because it can ignore an illegal rotate value
				// and doesn't have a set_gamma() function.
				compatible = "ilitek,ili9341";
				reg = <0>; // Chip Select 0

				spi-max-frequency = <32000000>; // 32MHz

				reset-gpios = <&gpio 6 1>; // reset is active low hence the 1
				dc-gpios = <&gpio 5 0>;

				width = <320>;
				height = <240>;
				buswidth = <8>; // Most controllers use this value

				// This is a hack to prevent fb_s6d02a1.c:set_var() from issuing
				// command 0x36 after the init sequence has been applied and thus
				// changing the config.
				rotate = <1>;

				// see drivers/staging/fbtft/fb_ili9341.c:init_display() for how this looks in the driver
				// Command 0x36 is taken from the fb_ili9341.c:set_var() function.
				init = <0x1000001
					0x2000005
					0x1000028
					0x10000cf 0x00 0x83 0x30
					0x10000ed 0x64 0x03 0x12 0x81
					0x10000e8 0x85 0x01 0x79
					0x10000cb 0x39 0x2c 0x00 0x34 0x02
					0x10000f7 0x20
					0x10000ea 0x00 0x00
					0x10000c0 0x26
					0x10000c1 0x11
					0x10000c5 0x35 0x3e
					0x10000c7 0xbe
					0x100003a 0x55
					0x1000036 0x28
					0x10000b1 0x00 0x1b
					0x1000026 0x01
					0x10000f2 0x08
					0x1000026 0x01
					0x10000e0 0x1f 0x1a 0x18 0x0a 0x0f 0x06 0x45 0x87 0x32 0x0a 0x07 0x02 0x07 0x05 0x00
					0x10000e1 0x00 0x25 0x27 0x05 0x10 0x09 0x3a 0x78 0x4d 0x05 0x18 0x0d 0x38 0x3a 0x1f
					0x10000b7 0x07
					0x10000b6 0x0a 0x82 0x27 0x00
					0x1000011
					0x2000064
					0x1000029
					0x2000064>;

				debug = <0x4000000>; // print init commands to the kernel log
			};
		};
	};
};

请根据自己的接线修改引脚：

• reset-gpios：LCD 的RES引脚
• dc-gpios：LCD的DC引脚

init为LCD的初始化指令。

编译DTS

在命令行中，执行如下命令：

dtc -o ili9341.dtbo ili9341.dts

将编译好的dtbo文件复制到/boot/overlays/：

sudo cp ili9341.dtbo /boot/overlays/

配置overlays

打开/boot/config.txt文件，在文件末尾添加如下内容：

dtoverlay=ili9341

保存并重新启动系统。在系统启动完成后，在命令行执行命令：

dmesg

可以看到TFT的Framebuffer内核日志信息：

[   40.657276] fbtft: module is from the staging directory, the quality is unknown, you have been warned.
[   40.911475] fb_ili9341: module is from the staging directory, the quality is unknown, you have been warned.
[   41.314042] SPI driver fb_ili9341 has no spi_device_id for ilitek,ili9341
[   41.314487] fb_ili9341 spi0.0: fbtft_property_value: width = 320
[   41.314532] fb_ili9341 spi0.0: fbtft_property_value: height = 240
[   41.314562] fb_ili9341 spi0.0: fbtft_property_value: buswidth = 8
[   41.314594] fb_ili9341 spi0.0: fbtft_property_value: debug = 67108864
[   41.314620] fb_ili9341 spi0.0: fbtft_property_value: rotate = 1
[   41.457358] cfg80211: Loading compiled-in X.509 certificates for regulatory database
[   41.515507] fb_ili9341 spi0.0: init: write_register:
[   41.515554] fb_ili9341 spi0.0: buf[0] = 01
[   41.515705] fb_ili9341 spi0.0: init: msleep(5)
[   41.547050] fb_ili9341 spi0.0: init: write_register:
[   41.547097] fb_ili9341 spi0.0: buf[0] = 28
[   41.549533] fb_ili9341 spi0.0: init: write_register:
[   41.549576] fb_ili9341 spi0.0: buf[0] = CF
[   41.549607] fb_ili9341 spi0.0: buf[1] = 00
[   41.549628] fb_ili9341 spi0.0: buf[2] = 83
[   41.549649] fb_ili9341 spi0.0: buf[3] = 30
[   41.550784] fb_ili9341 spi0.0: init: write_register:
[   41.550821] fb_ili9341 spi0.0: buf[0] = ED
[   41.550848] fb_ili9341 spi0.0: buf[1] = 64
[   41.550868] fb_ili9341 spi0.0: buf[2] = 03
[   41.550888] fb_ili9341 spi0.0: buf[3] = 12
[   41.550907] fb_ili9341 spi0.0: buf[4] = 81
[   41.551978] fb_ili9341 spi0.0: init: write_register:
[   41.552019] fb_ili9341 spi0.0: buf[0] = E8
[   41.552045] fb_ili9341 spi0.0: buf[1] = 85
[   41.552067] fb_ili9341 spi0.0: buf[2] = 01
[   41.552088] fb_ili9341 spi0.0: buf[3] = 79
[   41.556254] fb_ili9341 spi0.0: init: write_register:
[   41.556350] fb_ili9341 spi0.0: buf[0] = CB
[   41.556382] fb_ili9341 spi0.0: buf[1] = 39
[   41.556404] fb_ili9341 spi0.0: buf[2] = 2C
[   41.556424] fb_ili9341 spi0.0: buf[3] = 00
[   41.556444] fb_ili9341 spi0.0: buf[4] = 34
[   41.556464] fb_ili9341 spi0.0: buf[5] = 02
[   41.558014] fb_ili9341 spi0.0: init: write_register:
[   41.558055] fb_ili9341 spi0.0: buf[0] = F7
[   41.558083] fb_ili9341 spi0.0: buf[1] = 20
[   41.559167] fb_ili9341 spi0.0: init: write_register:
[   41.559208] fb_ili9341 spi0.0: buf[0] = EA
[   41.559236] fb_ili9341 spi0.0: buf[1] = 00
[   41.559257] fb_ili9341 spi0.0: buf[2] = 00
[   41.561600] fb_ili9341 spi0.0: init: write_register:
[   41.561643] fb_ili9341 spi0.0: buf[0] = C0
[   41.561672] fb_ili9341 spi0.0: buf[1] = 26
[   41.561848] fb_ili9341 spi0.0: init: write_register:
[   41.561904] fb_ili9341 spi0.0: buf[0] = C1
[   41.561935] fb_ili9341 spi0.0: buf[1] = 11
[   41.566661] fb_ili9341 spi0.0: init: write_register:
[   41.566706] fb_ili9341 spi0.0: buf[0] = C5
[   41.566736] fb_ili9341 spi0.0: buf[1] = 35
[   41.566757] fb_ili9341 spi0.0: buf[2] = 3E
[   41.569197] fb_ili9341 spi0.0: init: write_register:
[   41.569236] fb_ili9341 spi0.0: buf[0] = C7
[   41.569267] fb_ili9341 spi0.0: buf[1] = BE
[   41.569440] fb_ili9341 spi0.0: init: write_register:
[   41.569465] fb_ili9341 spi0.0: buf[0] = 3A
[   41.569489] fb_ili9341 spi0.0: buf[1] = 55
[   41.571529] fb_ili9341 spi0.0: init: write_register:
[   41.571572] fb_ili9341 spi0.0: buf[0] = 36
[   41.571600] fb_ili9341 spi0.0: buf[1] = 28
[   41.580923] fb_ili9341 spi0.0: init: write_register:
[   41.580969] fb_ili9341 spi0.0: buf[0] = B1
[   41.580998] fb_ili9341 spi0.0: buf[1] = 00
[   41.581019] fb_ili9341 spi0.0: buf[2] = 1B
[   41.588734] fb_ili9341 spi0.0: init: write_register:
[   41.588781] fb_ili9341 spi0.0: buf[0] = 26
[   41.588811] fb_ili9341 spi0.0: buf[1] = 01
[   41.633770] fb_ili9341 spi0.0: init: write_register:
[   41.633816] fb_ili9341 spi0.0: buf[0] = F2
[   41.633847] fb_ili9341 spi0.0: buf[1] = 08
[   41.636043] fb_ili9341 spi0.0: init: write_register:
[   41.636086] fb_ili9341 spi0.0: buf[0] = 26
[   41.636116] fb_ili9341 spi0.0: buf[1] = 01
[   41.669646] fb_ili9341 spi0.0: init: write_register:
[   41.669691] fb_ili9341 spi0.0: buf[0] = E0
[   41.669720] fb_ili9341 spi0.0: buf[1] = 1F
[   41.669740] fb_ili9341 spi0.0: buf[2] = 1A
[   41.669759] fb_ili9341 spi0.0: buf[3] = 18
[   41.669779] fb_ili9341 spi0.0: buf[4] = 0A
[   41.669800] fb_ili9341 spi0.0: buf[5] = 0F
[   41.669819] fb_ili9341 spi0.0: buf[6] = 06
[   41.669838] fb_ili9341 spi0.0: buf[7] = 45
[   41.669857] fb_ili9341 spi0.0: buf[8] = 87
[   41.669877] fb_ili9341 spi0.0: buf[9] = 32
[   41.669897] fb_ili9341 spi0.0: buf[10] = 0A
[   41.669918] fb_ili9341 spi0.0: buf[11] = 07
[   41.669938] fb_ili9341 spi0.0: buf[12] = 02
[   41.669958] fb_ili9341 spi0.0: buf[13] = 07
[   41.669977] fb_ili9341 spi0.0: buf[14] = 05
[   41.669997] fb_ili9341 spi0.0: buf[15] = 00
[   41.683625] fb_ili9341 spi0.0: init: write_register:
[   41.683670] fb_ili9341 spi0.0: buf[0] = E1
[   41.683788] fb_ili9341 spi0.0: buf[1] = 00
[   41.683815] fb_ili9341 spi0.0: buf[2] = 25
[   41.683838] fb_ili9341 spi0.0: buf[3] = 27
[   41.683859] fb_ili9341 spi0.0: buf[4] = 05
[   41.683879] fb_ili9341 spi0.0: buf[5] = 10
[   41.683899] fb_ili9341 spi0.0: buf[6] = 09
[   41.683919] fb_ili9341 spi0.0: buf[7] = 3A
[   41.683939] fb_ili9341 spi0.0: buf[8] = 78
[   41.683958] fb_ili9341 spi0.0: buf[9] = 4D
[   41.683977] fb_ili9341 spi0.0: buf[10] = 05
[   41.683998] fb_ili9341 spi0.0: buf[11] = 18
[   41.684019] fb_ili9341 spi0.0: buf[12] = 0D
[   41.684038] fb_ili9341 spi0.0: buf[13] = 38
[   41.684059] fb_ili9341 spi0.0: buf[14] = 3A
[   41.684079] fb_ili9341 spi0.0: buf[15] = 1F
[   41.693430] fb_ili9341 spi0.0: init: write_register:
[   41.693474] fb_ili9341 spi0.0: buf[0] = B7
[   41.693504] fb_ili9341 spi0.0: buf[1] = 07
[   41.707164] fb_ili9341 spi0.0: init: write_register:
[   41.707209] fb_ili9341 spi0.0: buf[0] = B6
[   41.707240] fb_ili9341 spi0.0: buf[1] = 0A
[   41.707261] fb_ili9341 spi0.0: buf[2] = 82
[   41.707283] fb_ili9341 spi0.0: buf[3] = 27
[   41.707303] fb_ili9341 spi0.0: buf[4] = 00
[   41.719204] fb_ili9341 spi0.0: init: write_register:
[   41.719250] fb_ili9341 spi0.0: buf[0] = 11
[   41.721594] fb_ili9341 spi0.0: init: msleep(100)
[   41.833878] fb_ili9341 spi0.0: init: write_register:
[   41.833925] fb_ili9341 spi0.0: buf[0] = 29
[   41.834076] fb_ili9341 spi0.0: init: msleep(100)

在设备目录中，我们将可以看到有两个framebuffer设备文件，fb0，fb1，其中fb1就是我们的TFT LCD的Framebuffer设备。

从内核日志输出可以知道，fb_ili9341已经启动。结果如下：