上节使用fbtft来驱动SPI接口TFT屏幕，但是是编译进内核的方式。
本节再来测试下编译成模块的用法。
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，把上节添加的节点注释掉，避免干扰本节的测试。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 = <96000000>;
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";
};
编辑Device
根据Linux统一设备模型思想：Device提供硬件信息描述，Driver提供使用硬件信息的方法。
我们打开 /kernel/driver/staging/fbtft/fbtft_device.c文件，看到
static struct fbtft_device_display displays[] = {
{
.name = "adafruit18",
.spi = &(struct spi_board_info) {
.modalias = "fb_st7735r",
.max_speed_hz = 32000000,
.mode = SPI_MODE_0,
.platform_data = &(struct fbtft_platform_data) {
.display = {
.buswidth = 8,
.backlight = 1,
},
.gamma = ADAFRUIT18_GAMMA,
}
}
}, {
.name = "adafruit18_green",
.spi = &(struct spi_board_info) {
.modalias = "fb_st7735r",
.max_speed_hz = 4000000,
.mode = SPI_MODE_0,
.platform_data = &(struct fbtft_platform_data) {
.display = {
.buswidth = 8,
.backlight = 1,
.fbtftops.set_addr_win =
adafruit18_green_tab_set_addr_win,
},
.bgr = true,
.gamma = ADAFRUIT18_GAMMA,
}
}
}, {
......................省略
上面的结构体描述了大量的显示屏信息，我们在最后面仿造前面的，加上ST7789VW屏幕的描述
}, {
.name = "qlexceltft", //你自己取，后面加载模块的时候要用
.spi = &(struct spi_board_info) {
.modalias = "fb_st7789vW", //匹配显示屏的名字
.max_speed_hz = 96000000, //最大SPI速率
.mode = SPI_MODE_0, //spi的模式
.bus_num=0, //使用SPI0
.chip_select = 0, //使用SPI0的CS0管脚
.platform_data = &(struct fbtft_platform_data) {
.display = {
.buswidth = 8, //8位总线
.backlight = 1, //有背光
},
// .bgr = true,
.gpios = (const struct fbtft_gpio []) {
{ "reset", 203 }, //PG11 reset占用的管脚号
{ "dc", 1 }, //PA1 dc占用的管脚号
{ "led", 0 }, //PA0 背光占用的管脚号
},
}
}
}
添加Driver
接着我们修改位于统一设备模型中的driver
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 <linux/bitops.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <video/mipi_display.h>
#include <linux/gpio.h>
#include "fbtft.h"
#define DRVNAME "fb_st7789vw"
#define DEFAULT_GAMMA \
"D0 04 0D 11 13 2B 3F 54 4C 18 0D 0B 1F 23\n" \
"D0 04 0C 11 13 2C 3F 44 51 2F 1F 1F 20 23"
/**
* enum st7789v_command - ST7789V display controller commands
*
* @PORCTRL: porch setting
* @GCTRL: gate control
* @VCOMS: VCOM setting
* @VDVVRHEN: VDV and VRH command enable
* @VRHS: VRH set
* @VDVS: VDV set
* @VCMOFSET: VCOM offset set
* @PWCTRL1: power control 1
* @PVGAMCTRL: positive voltage gamma control
* @NVGAMCTRL: negative voltage gamma control
*
* The command names are the same as those found in the datasheet to ease
* looking up their semantics and usage.
*
* Note that the ST7789V display controller offers quite a few more commands
* which have been omitted from this list as they are not used at the moment.
* Furthermore, commands that are compliant with the MIPI DCS have been left
* out as well to avoid duplicate entries.
*/
enum st7789v_command {
PORCTRL = 0xB2,
GCTRL = 0xB7,
VCOMS = 0xBB,
LCMCTRL = 0xC0,
VDVVRHEN = 0xC2,
VRHS = 0xC3,
VDVS = 0xC4,
VCMOFSET = 0xC5,
FRCTRL2 = 0xC6,
PWCTRL1 = 0xD0,
PVGAMCTRL = 0xE0,
NVGAMCTRL = 0xE1,
};
#define MADCTL_BGR BIT(3) /* bitmask for RGB/BGR order */
#define MADCTL_MV BIT(5) /* bitmask for page/column order */
#define MADCTL_MX BIT(6) /* bitmask for column address order */
#define MADCTL_MY BIT(7) /* bitmask for page address order */
/**
* init_display() - initialize the display controller
*
* @par: FBTFT parameter object
*
* Most of the commands in this init function set their parameters to the
* same default values which are already in place after the display has been
* powered up. (The main exception to this rule is the pixel format which
* would default to 18 instead of 16 bit per pixel.)
* Nonetheless, this sequence can be used as a template for concrete
* displays which usually need some adjustments.
*
* Return: 0 on success, < 0 if error occurred.
*/
static int init_display(struct fbtft_par *par)
{
/* turn off sleep mode */
write_reg(par, MIPI_DCS_EXIT_SLEEP_MODE);
mdelay(120);
write_reg(par, MIPI_DCS_SET_ADDRESS_MODE, 0x0);
write_reg(par, MIPI_DCS_SET_PIXEL_FORMAT, MIPI_DCS_PIXEL_FMT_16BIT);
write_reg(par, PORCTRL, 0x0C, 0x0C, 0x00, 0x33, 0x33);
write_reg(par, GCTRL, 0x35);
write_reg(par, VCOMS, 0x19);
write_reg(par, LCMCTRL, 0x2C);
write_reg(par, VDVVRHEN, 0x01);
write_reg(par, VRHS, 0x12);
write_reg(par, VDVS, 0x20);
write_reg(par, FRCTRL2, 0x0F);
write_reg(par, PWCTRL1, 0xA4, 0xA1);
write_reg(par, MIPI_DCS_ENTER_INVERT_MODE);
write_reg(par, MIPI_DCS_SET_DISPLAY_ON);
return 0;
}
static void set_addr_win(struct fbtft_par *par, int xs, int ys, int xe, int ye)
{
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);
}
/**
* set_var() - apply LCD properties like rotation and BGR mode
*
* @par: FBTFT parameter object
*
* Return: 0 on success, < 0 if error occurred.
*/
static int set_var(struct fbtft_par *par)
{
u8 madctl_par = 0;
if (par->bgr)
madctl_par |= MADCTL_BGR;
switch (par->info->var.rotate) {
case 0:
break;
case 90:
madctl_par |= (MADCTL_MV | MADCTL_MY);
break;
case 180:
madctl_par |= (MADCTL_MX | MADCTL_MY);
break;
case 270:
madctl_par |= (MADCTL_MV | MADCTL_MX);
break;
default:
return -EINVAL;
}
write_reg(par, MIPI_DCS_SET_ADDRESS_MODE, madctl_par);
return 0;
}
/**
* set_gamma() - set gamma curves
*
* @par: FBTFT parameter object
* @curves: gamma curves
*
* Before the gamma curves are applied, they are preprocessed with a bitmask
* to ensure syntactically correct input for the display controller.
* This implies that the curves input parameter might be changed by this
* function and that illegal gamma values are auto-corrected and not
* reported as errors.
*
* Return: 0 on success, < 0 if error occurred.
*/
static int set_gamma(struct fbtft_par *par, u32 *curves)
{
int i;
int j;
int c; /* curve index offset */
/*
* Bitmasks for gamma curve command parameters.
* The masks are the same for both positive and negative voltage
* gamma curves.
*/
static const u8 gamma_par_mask[] = {
0xFF, /* V63[3:0], V0[3:0]*/
0x3F, /* V1[5:0] */
0x3F, /* V2[5:0] */
0x1F, /* V4[4:0] */
0x1F, /* V6[4:0] */
0x3F, /* J0[1:0], V13[3:0] */
0x7F, /* V20[6:0] */
0x77, /* V36[2:0], V27[2:0] */
0x7F, /* V43[6:0] */
0x3F, /* J1[1:0], V50[3:0] */
0x1F, /* V57[4:0] */
0x1F, /* V59[4:0] */
0x3F, /* V61[5:0] */
0x3F, /* V62[5:0] */
};
for (i = 0; i < par->gamma.num_curves; i++) {
c = i * par->gamma.num_values;
for (j = 0; j < par->gamma.num_values; j++)
curves[c + j] &= gamma_par_mask[j];
write_reg(
par, PVGAMCTRL + i,
curves[c + 0], curves[c + 1], curves[c + 2],
curves[c + 3], curves[c + 4], curves[c + 5],
curves[c + 6], curves[c + 7], curves[c + 8],
curves[c + 9], curves[c + 10], curves[c + 11],
curves[c + 12], curves[c + 13]);
}
return 0;
}
/**
* blank() - blank the display
*
* @par: FBTFT parameter object
* @on: whether to enable or disable blanking the display
*
* Return: 0 on success, < 0 if error occurred.
*/
static int blank(struct fbtft_par *par, bool on)
{
if (on)
write_reg(par, MIPI_DCS_SET_DISPLAY_OFF);
else
write_reg(par, MIPI_DCS_SET_DISPLAY_ON);
return 0;
}
static struct fbtft_display display = {
.regwidth = 8,
.width = 240,
.height = 240,
.gamma_num = 2,
.gamma_len = 14,
.gamma = DEFAULT_GAMMA,
.fbtftops = {
.init_display = init_display,
.set_addr_win = set_addr_win,
.set_var = set_var,
.set_gamma = set_gamma,
.blank = blank,
},
};
FBTFT_REGISTER_DRIVER(DRVNAME, "sitronix,st7789vw", &display);
MODULE_ALIAS("spi:" DRVNAME);
MODULE_ALIAS("platform:" DRVNAME);
MODULE_ALIAS("spi:st7789vw");
MODULE_ALIAS("platform:st7789vw");
MODULE_DESCRIPTION("FB driver for the ST7789VW LCD Controller");
MODULE_AUTHOR("FriendlyElec");
MODULE_LICENSE("GPL");
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 --->
将FB driver for the ST7789VW LCD Controller和Module to for adding FBTFT devices选择成模块
# 编译内核、设备树、模块
make zImage dtbs modules ARCH=arm CROSS_COMPILE=arm-linux-
# 网络更新内核
scp arch/arm/boot/zImage root@192.168.0.101:/boot
# 网络更新设备树
scp arch/arm/boot/dts/sun8i-h3-nanopi-neo-air.dtb root@192.168.0.101:/boot
# 网络上传模块
scp drivers/staging/fbtft/fbtft_device.ko root@192.168.0.101:/lib/modules/4.14.111/
scp drivers/staging/fbtft/fb_st7789vw.ko root@192.168.0.101:/lib/modules/4.14.111/
上电测试
上电后，切换root，加载模块
insmod fbtft_device.ko name=qlexceltft busnum=0 cs=0 rotate=0 debug=7
insmod fb_st7789vw.ko
insmod fbtft_device.ko后面的参数解释如下：
- name：fbtft_device里你自己设置的
- busnum：用于指定使用第几个spi控制器
- CS：SPI的第几个CS片选线
- rotate：屏幕翻转角度
- debug：数字越大，调试的时候打印的信息越多，debug的时候可以设置为7.
执行成功的话屏幕应该点亮了，通过lsmod命令就能看到模块已被加载，在/dev目录下，会产生fb0设备，如果执行失败，可以通过dmesg | grep "fb" 来查看内核日志，分析具体原因，一般都是由于参数错了导致；
设置开机自动加载模块
1、在st7735s.ko fbtft_device.ko 驱动模块目录下（/lib/modules/4.x.x/kernel/driver/staging/fbtft）执行sudo depmod -A 生成map文件。
2、编辑文件 /etc/modules，添加如下：
fb_st7735s
fbtft_device
3、新建配置文件 /etc/modprobe.d/fbtft.conf，内容如下：
options fbtft_device name=qlexceltft busnum=0 gpios=reset:3,dc:17 rotate=90 custom=1 height=128 width=128
4、上面 3 步完成后重启，应该就可以看到屏幕被点亮并显示了 console，说明驱动被自动加载了