Neza-D1开发板学习之SPI-LCD灯篇

[xfdr0805]

1. Neza-D1开发板芯片很强，但是没有引出RGB接口，板上引出了HDMI与MIPI接口，没引出RGB接口，手里的RGB接口的屏用不上了，扩展IO上有引出SPI1接口，看了一下尺寸，刚好可以放的下2.8”的SPI屏幕，正好手里有以前剩下的屏幕，就画了一块扩展板(可惜芯片是BGA封装，即使我能画出来，也没本事焊上啊！)，驱动芯片是ili9341 4线SPI，又加了一个触摸芯片上去，如下图
   
2. 设备树配置

    lcd_ili9341@0 {
		#address-cells = <1>;
		#size-cells = <1>;
		compatible = "ilitek,ili9341";
		reg = <0>;
		spi-max-frequency = <32000000>;
		rotation = <0>;
		spi-cpol;
		spi-cpha;
		rgb;
		fps = <30>;
		buswidth = <8>;
		txbuflen = <32768>;
		reset-gpios = <&pcf8574 6 GPIO_ACTIVE_LOW>;
		dc-gpios = <&pcf8574 7 GPIO_ACTIVE_LOW>;
		/*backlight = <&backlight>;*/
		led-gpios = <&pcf8574 5 GPIO_ACTIVE_HIGH>;
		status = "okay";
    };

3. 在内核打开small lcd support选项

   [] Staging drivers --->
   <> Support for small TFT LCD display modules --->3
   <*> FB driver for the ILI9341 LCD Controller

4. 系统启动log

    [    2.670067] fbtft_of_value: buswidth = 8
    [    2.674512] fbtft_of_value: backlight = 39
    [    2.679097] fbtft_of_value: fps = 30
    [    2.683098] fbtft_of_value: txbuflen = 32768
    [    2.691259] GPT:Primary header thinks Alt. header is not at the end of the disk.
    [    2.699560] GPT:625184 != 7774207
    [    2.703265] GPT:Alternate GPT header not at the end of the disk.
    [    2.709981] GPT:625184 != 7774207
    [    2.713688] GPT: Use GNU Parted to correct GPT errors.
    [    2.719480]  mmcblk0: p1 p2 p3 p4
    [    2.987837] random: fast init done
    [    3.036258] graphics fb1: fb_ili9341 frame buffer, 240x320, 150 KiB video memory, 32 KiB buffer memory, fps=31, spi1.0 at 32 MHz

5. 这里有一点需要注意，我们使用的GPIO是通过PCF8574扩展出来的，对IO读写操作时可能会导致休眠，因此不能在中断函数里使用，我们需要简单的修改一下驱动文件，用一个宏定义即可,如果不修改操作一次IO，就会出现一堆警告

   #define gpio_set_value gpio_set_value_cansleep

6. 进系统里可以查看是否有对应设备

    # ls /dev/fb*
    /dev/fb0  /dev/fb1
    测试屏幕
    # cat /dev/urandom > /dev/fb1
    cat: write error: No space left on device
    清屏
    # cat /dev/zero > /dev/fb1
    cat: write error: No space left on device
    显示图片
    # fbv image1.jpg