嵌入式Linux：LCD背光电路记录（V3s）

• Uboot配置
• 适配mangopi

到处都是知识点！

背光芯片：

• PT4101
• PT4103
• LP3380
• SY7201

Licheepi背光电路原理图
Cherrypi背光电路原理图

mangopi背光电路原理图

PB引脚系列系列

在licheepi的uboot里面有相关配置：
路径：u-boot-3s-current/configs/LicheePi_Zero_800x480LCD_defconfig

CONFIG_ARM=y
CONFIG_ARCH_SUNXI=y
# CONFIG_ARMV7_NONSEC is not set
CONFIG_MACH_SUN8I_V3S=y
CONFIG_DRAM_CLK=360
CONFIG_DRAM_ZQ=14779
CONFIG_VIDEO_LCD_MODE="x:800,y:480,depth:18,pclk_khz:33000,le:87,ri:40,up:31,lo:13,hs:1,vs:1,sync:3,vmode:0"
CONFIG_VIDEO_LCD_BL_PWM="PB4"
# CONFIG_VIDEO_LCD_BL_PWM_ACTIVE_LOW is not set
CONFIG_DEFAULT_DEVICE_TREE="sun8i-v3s-licheepi-zero"
# CONFIG_CONSOLE_MUX is not set
CONFIG_SPL=y
CONFIG_CMD_BOOTMENU=y
# CONFIG_CMD_IMLS is not set
CONFIG_CMD_MEMINFO=y
# CONFIG_CMD_FLASH is not set
# CONFIG_CMD_FPGA is not set
# CONFIG_NETDEVICES is not set
CONFIG_OF_LIBFDT_OVERLAY=y

这里只定义了：CONFIG_VIDEO_LCD_BL_PWM="PB4"

官方的固件，电压点测量：

• C136：19.09v
• LCD_BL_EN(R119)：3.26v
• LCD_PWM0(R117)：0.7v

Lichee的固件

• C136：4.99v
• LCD_BL_EN(R119)：0v
• LCD_PWM0(R117)：2.62v

怪不得点不亮

于是我修改了一下licheepi的uboot的配置文件

CONFIG_ARM=y
CONFIG_ARCH_SUNXI=y
# CONFIG_ARMV7_NONSEC is not set
CONFIG_MACH_SUN8I_V3S=y
CONFIG_DRAM_CLK=360
CONFIG_DRAM_ZQ=14779
CONFIG_VIDEO_LCD_MODE="x:800,y:480,depth:18,pclk_khz:33000,le:87,ri:40,up:31,lo:13,hs:1,vs:1,sync:3,vmode:0"
CONFIG_VIDEO_LED_BL_EN="PB4"
CONFIG_VIDEO_LCD_BL_PWM="PB2"
# CONFIG_VIDEO_LCD_BL_PWM_ACTIVE_LOW is not set
CONFIG_DEFAULT_DEVICE_TREE="sun8i-v3s-licheepi-zero"
# CONFIG_CONSOLE_MUX is not set
CONFIG_SPL=y
CONFIG_CMD_BOOTMENU=y
# CONFIG_CMD_IMLS is not set
CONFIG_CMD_MEMINFO=y
# CONFIG_CMD_FLASH is not set
# CONFIG_CMD_FPGA is not set
# CONFIG_NETDEVICES is not set
CONFIG_OF_LIBFDT_OVERLAY=y

屏幕亮了！

• C136：19.09v
• LCD_BL_EN(R119)：3.26v
• LCD_PWM0(R117)：0.7v