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6.5物联网RK3399项目开发实录-驱动开发之LCD显示屏使用（wulianjishu666）

news 2025/7/9 15:36:10

90款行业常用传感器单片机程序及资料【stm32,stc89c52,arduino适用】

链接：https://pan.baidu.com/s/1M3u8lcznKuXfN8NRoLYtTA?pwd=c53f
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LCD使用

简介

AIO-3399J开发板外置了两个LCD屏接口，一个是EDP，一个是LVDS，接口对应板子上的位置如下图：

_images/lcd_interface.jpg

LVDS屏

DTS配置

引脚配置

AIO-3399J的SDK有LVDS DSI的DTS文件：kernel/arch/arm64/boot/dts/rockchip/rk3399-firefly-aio-lvds.dts，从该文件中我们可以看到以下语句：

/ {model = "AIO Board lvds (Android)";compatible = "rockchip,android", "rockchip,rk3399-firefly-lvds", "rockchip,rk3399";test-power {status = "okay";};...&dsi {status = "okay";dsi_panel: panel {compatible ="simple-panel-dsi";reg = <0>;//ddc-i2c-bu//power-supply = <&vcc_lcd>;//pinctrl-0 = <&lcd_panel_reset &lcd_panel_enable>;backlight = <&backlight>;/*enable-gpios = <&gpio1 1 GPIO_ACTIVE_LOW>;reset-gpios = <&gpio4 29 GPIO_ACTIVE_LOW>;*/dsi,flags = <(MIPI_DSI_MODE_VIDEO | MIPI_DSI_MODE_VIDEO_BURST | MIPI_DSI_MODE_LPM | MIPI_DSI_MODE_EOT_PACKET)>;dsi,format = <MIPI_DSI_FMT_RGB888>;//bus-format = <MEDIA_BUS_FMT_RGB666_1X18>;dsi,lanes = <4>;dsi,channel = <0>;enable-delay-ms = <35>;prepare-delay-ms = <6>;unprepare-delay-ms = <0>;disable-delay-ms = <20>;size,width = <120>;size,height = <170>;status = "okay";...power_ctr: power_ctr {rockchip,debug = <0>;lcd_pwr_en: lcd-pwr-en {gpios = <&gpio3 16 GPIO_ACTIVE_HIGH>;pinctrl-names = "default";pinctrl-0 = <&lcd_panel_pwr_en>;rockchip,delay = <10>;};lcd_rst: lcd-rst {gpios = <&gpio2 27 GPIO_ACTIVE_HIGH>;pinctrl-names = "default";pinctrl-0 = <&lcd_panel_reset>;rockchip,delay = <6>;};};...&pinctrl {lcd-panel {lcd_panel_reset: lcd-panel-reset {rockchip,pins = <2 27 RK_FUNC_GPIO &pcfg_pull_down>;};lcd_panel_pwr_en: lcd-panel-pwr-en {rockchip,pins = <3 16 RK_FUNC_GPIO &pcfg_pull_down>;};};
};

这里定义了LCD的电源控制引脚：

lcd_pwr_en:(GPIO3_C0)GPIO_ACTIVE_HIGH
lcd_rst:(GPIO2_D3)GPIO_ACTIVE_HIGH

都是高电平有效，具体的引脚配置请参考《GPIO》一节。

配置背光

AIO-3399J开发板外置了一个背光接口用来控制屏幕背光，如下图所示：

_images/lcd_back_light.jpg

在DTS文件：kernel/arch/arm64/boot/dts/rockchip/rk3399-firefly-core.dtsi中配置了背光信息，如下：

/ {compatible = "rockchip,rk3399-firefly-core", "rockchip,rk3399";backlight: backlight {status = "disabled";compatible = "pwm-backlight";pwms = <&pwm0 0 25000 0>;brightness-levels = <0   1   2   3   4   5   6   78   9  10  11  12  13  14  1516  17  18  19  20  21  22  2324  25  26  27  28  29  30  3132  33  34  35  36  37  38  3940  41  42  43  44  45  46  4748  49  50  51  52  53  54  5556  57  58  59  60  61  62  6364  65  66  67  68  69  70  7172  73  74  75  76  77  78  7980  81  82  83  84  85  86  8788  89  90  91  92  93  94  9596  97  98  99 100 101 102 103104 105 106 107 108 109 110 111112 113 114 115 116 117 118 119120 121 122 123 124 125 126 127128 129 130 131 132 133 134 135136 137 138 139 140 141 142 143144 145 146 147 148 149 150 151152 153 154 155 156 157 158 159160 161 162 163 164 165 166 167168 169 170 171 172 173 174 175176 177 178 179 180 181 182 183184 185 186 187 188 189 190 191192 193 194 195 196 197 198 199200 201 202 203 204 205 206 207208 209 210 211 212 213 214 215216 217 218 219 220 221 222 223224 225 226 227 228 229 230 231232 233 234 235 236 237 238 239240 241 242 243 244 245 246 247248 249 250 251 252 253 254 255>;default-brightness-level = <200>;
};

pwms属性：配置PWM，范例里面默认使用pwm0，25000ns是周期(40 KHz)。LVDS需要加背光电源控制脚，在kernel/arch/arm64/boot/dts/rockchip/rk3399-firefly-aio-lvds.dts中可以看到以下语句：

&backlight {status = "okay";enable-gpios = <&gpio1 1 GPIO_ACTIVE_HIGH>;brightness-levels = < 150 151152 153 154 155 156 157 158 159160 161 162 163 164 165 166 167168 169 170 171 172 173 174 175176 177 178 179 180 181 182 183184 185 186 187 188 189 190 191192 193 194 195 196 197 198 199200 201 202 203 204 205 206 207208 209 210 211 212 213 214 215216 217 218 219 220 221 222 223224 225 226 227 228 229 230 231232 233 234 235 236 237 238 239240 241 242 243 244 245 246 247248 249 250 251 252 253 254 255>;
};

因此使用时需修改DTS文件。

brightness-levels属性：配置背光亮度数组，最大值为255，配置暗区和亮区，并把亮区数组做255的比例调节。比如范例中暗区是255-221，亮区是220-0。 default-brightness-level属性：开机时默认背光亮度，范围为0-255。具体请参考kernel中的说明文档：kernel/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt

配置显示时序

与EDP屏不同，LVDS屏的 Timing 写在DTS文件中，在kernel/arch/arm64/boot/dts/rockchip/rk3399-firefly-aio-lvds.dts中可以看到以下语句：

disp_timings: display-timings {native-mode = <&timing0>;timing0: timing0 {clock-frequency = <80000000>;hactive = <768>;vactive = <1024>;hsync-len = <20>;   //20, 50hback-porch = <130>; //50, 56hfront-porch = <150>;//50, 30vsync-len = <40>;vback-porch = <130>;vfront-porch = <136>;hsync-active = <0>;vsync-active = <0>;de-active = <0>;pixelclk-active = <0>;};}
}

时序属性参考下图：

_images/lcd_sequence.jpg

Init Code

lvds屏上完电后需要发送初始化指令才能使之工作。初始化指令需要以下工具文档生成，下载TC358764_5_774_5XBG_DSI-LVDS_Tv11p_nm_1280x800.xls

如何配置LVDS panel-init-sequence

以1280x800单lvds为例: 首先打开TC358764_5_774_5XBG_DSI-LVDS_Tv11p_nm_1280x800.xls

选择页面”Timing Parameters_SYNC_EVENT”，按照LVDS屏的时序填入LVDS timing黄色单元,一般只需填入以下单元即可。

HPW / HBPR / HDISPR / HFPR 分别对应 hsync-len / hback-porch / hactive / hfront-porch
VPW / VBPR / VDISPR / VFPR 分别对应 vhsync-len / vback-porch / vactive / vfront-porch

LVDS timing填入完成后还需配置常规参数

_images/parameter.png

1.根据LVDS屏规格书确认LVDS Link和LVDS output format并选择屏的参数。
2.计算LVDS clock(蓝色单元无法写入，需要黄色单元自动计算得出)，需要填入DSI Clock(HOST), Pixel Clock Source, Pixel Clock Divider。计算公式如下:DSI Clock/Pixel Clock Source/Pixel Clock Divider=LVDS Clock

填入上述黄色单元基本上完成配置，接下来选择页面”Source”即可看到转换后的Comment

_images/source.png

以上面为例”013C 00030005”，mipi command就应该是”29 02 06 3C 01 05 00 03 00”

29 : packet ID
02 : 2ms delay
06 : 6 bytes
3C 01 : address = 0x013C
00 03 00 05 : data=0x05000300

将页面source所有地址写入数据，即可完成初始化指令panel-init-sequence。

dts在kernel/arch/arm64/boot/dts/rockchip/rk3399-firefly-aio-lvds.dts中可以看到lvds的初始化指令列表：

&dsi {status = "okay";...panel-init-sequence = [29 00 06 3C 01 09 00 07 0029 00 06 14 01 06 00 00 0029 00 06 64 01 0B 00 00 0029 00 06 68 01 0B 00 00 0029 00 06 6C 01 0B 00 00 0029 00 06 70 01 0B 00 00 0029 00 06 34 01 1F 00 00 0029 00 06 10 02 1F 00 00 0029 00 06 04 01 01 00 00 0029 00 06 04 02 01 00 00 0029 00 06 50 04 20 01 F0 0329 00 06 54 04 32 00 B4 0029 00 06 58 04 80 07 48 0029 00 06 5C 04 0A 00 19 0029 00 06 60 04 38 04 0A 0029 00 06 64 04 01 00 00 0029 01 06 A0 04 06 80 44 0029 00 06 A0 04 06 80 04 0029 00 06 04 05 04 00 00 0029 00 06 80 04 00 01 02 0329 00 06 84 04 04 07 05 0829 00 06 88 04 09 0A 0E 0F29 00 06 8C 04 0B 0C 0D 1029 00 06 90 04 16 17 11 1229 00 06 94 04 13 14 15 1B29 00 06 98 04 18 19 1A 0629 02 06 9C 04 33 04 00 00];panel-exit-sequence = [05 05 01 2805 78 01 10];...
};

命令格式以及说明可参考以下附件： Rockchip DRM Panel Porting Guide.pdf

kernel 发送指令可以看到在kernel/drivers/gpu/drm/panel/panel-simple.c文件中的操作：

static int panel_simple_enable(struct drm_panel *panel)
{struct panel_simple *p = to_panel_simple(panel);int err;if (p->enabled)return 0;DBG("enter\n");if (p->on_cmds) {err = panel_simple_dsi_send_cmds(p, p->on_cmds);if (err)dev_err(p->dev, "failed to send on cmds\n");}if (p->desc && p->desc->delay.enable) {DBG("p->desc->delay.enable=%d\n", p->desc->delay.enable);msleep(p->desc->delay.enable);}if (p->backlight) {DBG("open backlight\n");p->backlight->props.power = FB_BLANK_UNBLANK;backlight_update_status(p->backlight);}p->enabled = true;return 0;
}

u-boot

发送指令可以看到在u-boot/drivers/video/rockchip-dw-mipi-dsi.c文件中的操作：

static int rockchip_dw_mipi_dsi_enable(struct display_state *state)
{struct connector_state *conn_state = &state->conn_state;struct crtc_state *crtc_state = &state->crtc_state;const struct rockchip_connector *connector = conn_state->connector;const struct dw_mipi_dsi_plat_data *pdata = connector->data;struct dw_mipi_dsi *dsi = conn_state->private;u32 val;DBG("enter\n");dw_mipi_dsi_set_mode(dsi, DW_MIPI_DSI_VID_MODE);dsi_write(dsi, DSI_MODE_CFG, ENABLE_CMD_MODE);dw_mipi_dsi_set_mode(dsi, DW_MIPI_DSI_VID_MODE);if (!pdata->has_vop_sel)return 0;if (pdata->grf_switch_reg) {if (crtc_state->crtc_id)val = pdata->dsi0_en_bit | (pdata->dsi0_en_bit << 16);elseval = pdata->dsi0_en_bit << 16;writel(val, RKIO_GRF_PHYS + pdata->grf_switch_reg);}debug("vop %s output to dsi0\n", (crtc_state->crtc_id) ? "LIT" : "BIG");//rockchip_dw_mipi_dsi_read_allregs(dsi);return 0;
}

常见问题

1. 画面抖动闪屏

排查屏参数是否超出屏规格书限定周期，排查屏时钟大小。”Timing Parameters_SYNC_EVENT”所有参数变动必须和comment同步调整。

2. 颜色显示异常

尝试同步调整color mapping或者lvds timing。

NOTE: 页面”How to use”有详细步骤，其他参数说明可以参考文档”页面”菜单。