ZedBoard Linux开发 ---- OLED驱动详解

http://blog.163.com/thinki_cao/blog/static/8394487520143193932495/

ZedBoard上有一个128x32的OLED，默认情况下启动Digilent OOB Design的镜像之后显示的是“Digilent”的logo，不过既然能显示logo，那么也就是说其实在Digilent
Linux中已经提供了Linux的驱动，那么这就是一个很好的学习资料。在ZedBoard自带的SD卡镜像中，oled的驱动是作为模块驱动在启动时加载的，脚本如下：

zynq> cat /usr/bin/load_oled                                                       #!/bin/sh                                                                          insmod /lib/modules/`uname -r`/pmodoled-gpio.ko;                                                                                                                      if [ -c /dev/zed_oled ]; then                                                              cat /root/logo.bin > /dev/zed_oled;                                        fi;

可以看到，加载驱动也就是简单地insmod ko文件，此时会在/dev目录下自动生成zed_oled设备节点（这是由于zedboard的ramdisk移植了mdev，可以理解为嵌入式版的udev，解释到此为止，有兴趣的可以去搜搜udev），同时还提供了一个脚本来卸载该模块，此时oled上就会全屏清空，脚本如下：

zynq> cat /usr/bin/unload_oled                                                     #!/bin/sh                                                                          rmmod pmodoled-gpio /lib/modules/`uname -r`/pmodoled-gpio.ko;

所以在zedboard的getting started文档中就有这样一个demo，不过在新版的digilent内核中（我的是3.6）oled驱动已经被编译到内核中去了，所以load/unload操作没有效果，不过既然cat /root/logo.bin > /dev/zed_oled有效，那么我们也可以试试其他bin文件是否有效，经过一番摸索，最终明白了zedboard上的oled是从右往左扫描，从上往下扫描，一共四行。由于从图片转bin文件的软件linux下实在难找，所以最终我只能使用了Img2Lcd（还好电脑里面装了wine
:-) ），具体的配置如下图中Img2Lcd所示(注意图片大小是128x32）：



注意左下角两个打勾的选项，一个是从右往左扫描，另一个是字节内像素数据反序，最后保存成.bin格式的即可。下面我们启动ZedBoard Linux之后，将.bin二进制文件通过nfs拷贝过来，再用cat xxx.bin > /dev/zed_oled，那么就可以看到oled上面的图像发生了变化：



接下来的事情，大家依葫芦画瓢就好:-)

这里简要介绍内核中的驱动，驱动的源码位于linux-digilent/drivers/pmods/pmodoled-gpio.c，首先注册pmodoled-gpio平台设备驱动，通过设备树中展开的平台设备进行匹配从而跳转到.probe函数，在该函数中再注册spi驱动以及添加spi设备，通过spi总线匹配之后调用spi驱动的.probe函数，最终在该函数中我们可以找到熟悉的cdev_init,cdev_add,alloc_chrdev_region,class_create以及device_create等函数，那么到这里基本上驱动就可以分析完毕了，有兴趣的可以写一个C程序进行操作，以加深对驱动程序的理解，下面我给出一个最简单的demo来结束本篇博客：

#include <stdio.h>#include <stdlib.h>#include <sys/types.h>#include <fcntl.h>#include <unistd.h>unsigned char dis_buf[128*4]={0};const unsigned char gImage_logo_aa[512] = { /* 0X82,0X01,0X80,0X00,0X20,0X00, */0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X80,0X80,0X80,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X80,0X80,0X80,0X80,0X80,0X80,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X80,0X80,0X80,0X80,0X80,0X80,0X80,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X80,0XC0,0XC0,0X00,0X00,0X00,0X00,0XE0,0XE0,0X00,0X00,0X00,0X00,0X80,0X80,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0XC0,0XC0,0XC0,0XC0,0XC0,0XC0,0XC0,0XC0,0XC0,0XC0,0XC0,0X00,0X00,0XC0,0XC0,0XC0,0XC0,0XC0,0XC0,0XC0,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0XE0,0XE0,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0XFF,0XFF,0XFF,0X00,0X00,0X00,0X00,0X06,0X07,0X03,0X01,0X01,0X01,0X01,0X01,0X03,0X03,0X07,0X1E,0XFC,0XF8,0XE0,0X00,0X00,0X00,0X00,0X07,0X03,0X83,0X81,0X81,0XC1,0XC1,0XC3,0XE3,0XFF,0XFE,0X7C,0X00,0X00,0X00,0X00,0X00,0X18,0X18,0X1B,0X1B,0X19,0X18,0X18,0X18,0X18,0X18,0X19,0X1F,0XFE,0XF8,0X98,0X18,0X18,0X1F,0X1F,0X1C,0X00,0X00,0X00,0X00,0X00,0X00,0X80,0X8F,0X8C,0X88,0X88,0XF8,0XF8,0XC8,0X88,0X8C,0X8F,0X8F,0X00,0X00,0X3F,0X3F,0X30,0X30,0X30,0XF0,0XF0,0X00,0X00,0X00,0X00,0X00,0X00,0XC0,0XF0,0X7C,0X0C,0X00,0X00,0X00,0X00,0XFF,0XFF,0X00,0X00,0X00,0X00,0X3C,0XFC,0XE0,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0XFF,0XFF,0XFF,0X00,0X00,0X00,0X00,0XC0,0XC0,0X80,0X00,0X00,0X00,0X00,0X00,0X80,0X80,0XC0,0XF0,0X7F,0X3F,0X0F,0X00,0X00,0X00,0X7C,0XFF,0XFF,0XC7,0X83,0X03,0X03,0X01,0X01,0X01,0X80,0X80,0XC0,0X00,0X00,0X00,0X00,0X00,0X00,0X03,0X0F,0X1F,0X3B,0XF3,0XE3,0XC3,0XC3,0XE3,0X73,0X3B,0X1F,0X07,0X0F,0X1E,0X38,0X70,0XE0,0XC0,0X80,0X00,0X00,0X00,0X00,0X00,0X3F,0XBF,0XB0,0X30,0X30,0XFF,0XFF,0X30,0X30,0X30,0X3F,0X3F,0X00,0X00,0XFC,0XFC,0X04,0X04,0X04,0X07,0X07,0X00,0X00,0X00,0X00,0X78,0X7F,0X0F,0X01,0X00,0X00,0X00,0X00,0X00,0X00,0XFF,0XFF,0X00,0X00,0X00,0X00,0X00,0X01,0X0F,0X3F,0X78,0X60,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X03,0X03,0X03,0X00,0X00,0X00,0X00,0X00,0X01,0X01,0X03,0X03,0X03,0X03,0X03,0X03,0X01,0X01,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X01,0X01,0X03,0X03,0X03,0X03,0X03,0X03,0X03,0X01,0X01,0X00,0X00,0X00,0X00,0X04,0X0C,0X0C,0X06,0X06,0X07,0X03,0X03,0X01,0X01,0X03,0X03,0X06,0X06,0X0E,0X0C,0X0C,0X0C,0X00,0X00,0X01,0X03,0X01,0X00,0X00,0X00,0X0E,0X0F,0X07,0X06,0X06,0X06,0X07,0X0F,0X0C,0X0C,0X0C,0X0C,0X0C,0X0C,0X00,0X03,0X0F,0X0E,0X0C,0X0C,0X0C,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X0F,0X0F,0X0C,0X0C,0X0C,0X0C,0X0C,0X00,0X00,0X00,0X00,0X00,0X00,0X00,};int main(){  int fd = open("/dev/zed_oled",O_RDWR);  int i=0;  if( fd == -1){    printf("Can't open zed_oled device!\n");    return 0;  }  else{    printf("/dev/zed_oled open success!\n");  }    for(i=0;i<128*4;i++){      dis_buf[i]=0;    }        for(i=0; i<128*4 ; i++){      dis_buf[i]=gImage_logo_aa[i];    }    write(fd,dis_buf,128*4);
return 0;
}

pmodoled的驱动是很好的学习资料，有兴趣的读者可以互相交流