====== LCD @ Core-3568J ======

===== - 硬件信息 =====

==== - LCD接口 ====

=== 模块参数 ===

分辨率：128x160  \\
驱动芯片：ST7735S \\
接口类型：SPI \\
背光电流：30mA \\
电压：3.3V \\

=== 模块接口 ===

^  pin  ^ Name ^ Feature ^
^  1  | NC  | |
^  2  | GND | |
^  3  | LED- | |
^  4  | LED+ | |
^  5  | GND  | |
^  6  | /RESET | 复位，低有效 |
^  7  | A0 | 指令/数据， L：指令，H：数据 |
^  8  | SDA | |
^  9  | SCK | |
^  10  | VCC | 电源2.8~3.3v |
^  11  | IOVCC | IO电压2.8~3.3v |
^  12  | /CS  | 片选，低有效 |
^  13  | GND | |
^  14  | NC | |


==== - 控制接口 ====

^  No  ^ 信号     ^ pin@Core-3568J  ^ pin@rk3568    ^ GPIO      ^
^  1   | /RESET  | 169             | GPIO0_A6      |           |
^  2   | /CS     | 185             | SPI0_CS0_M0   | GPIO0_C6  |
^  3   | SCK     | 175             | SPI0_CLK_M0   | GPIO0_B5  |
^  4   | SDA     | 159             | SPI0_MOSI_M0  | GPIO0_B6  |
^  5   | CD      | 173             | GPIO0_C1      |           |
^  6   | BL      | 171             | GPIO0_C3      |           |

===== - Linux驱动设计（A） =====
采用gpio-leds + spidev方式连接LCD模块，模块端口信号采用两种驱动：
  * io:  /Reset,BL,CD信号，使用gpio-leds驱动
  * spi: /CS,SCK,SDA使用spidev驱动

==== - 控制IO ====
=== - dts ===
<code>
		lcd_reset: reset {
			label = "lcd:reset";
			linux,default-trigger = "none"; 
			default-state = "on";
			gpios = <&gpio0 RK_PA6 GPIO_ACTIVE_HIGH>;
		};

		lcd_backlight: backlight {
			label = "lcd:backlight";
			linux,default-trigger = "none"; 
			default-state = "on";
			gpios = <&gpio0 RK_PC3 GPIO_ACTIVE_HIGH>;
		};

		lcd_data: data {
			label = "lcd:data";
			linux,default-trigger = "none"; 
			default-state = "on";
			gpios = <&gpio0 RK_PC1 GPIO_ACTIVE_HIGH>;
		};
</code>
添加以上3个pin的gpio-leds节点，驱动成功后的访问入口为：
  /sys/class/leds/lcd:reset
  /sys/class/leds/lcd:backlight
  /sys/class/leds/lcd:data
  
可以用命令测试这几个pin的状态：
  # backlight = 1
  echo 1 > /sys/class/leds/lcd:backlight
  # backlight = 0
  echo 1 > /sys/class/leds/lcd:backlight
==== - spidev配置 ====
修改DTS及添加驱动到内核

=== - 内核配置spidev ===

  Device Drivers ‐‐‐> 
    [*] SPI support ‐‐‐> 
       <*> Rockchip SPI controller driver
       [*] User mode SPI device driver support

=== - dts配置 ===

  * rk3568-firefly-mplayer.dtsi

添加节点spi0 
<code>
&spi0 {
    status = "okay";
    max-freq = <50000000>;
    pinctrl-0 = <&spi0m0_cs0 &spi0m0_cs0 &spi0m0_pins>;
    pinctrl-1 = <&spi0m0_cs0 &spi0m0_cs0 &spi0m0_pins_hs>;	
    spidev@0 {
        compatible = "rockchip,spidev";
        reg = <0>; // CS0
        spi-max-frequency = <5000000>;
    };
};
</code>
  * pinctrl-0/1 重写覆盖了原定义，cs脚使用 spi0m0_cs1 代替 spi0m0_cs0
  * 停用冲突的管脚: uart8,pwm7等


  
==== - Demo script ====