Learning record: Character Bitmap display

2.2 LCD上顯示固定大小中英字體
需先安裝 LCD Driver，接著撰寫應用程式，導入HZK16漢字庫，將要顯示的字元，透過漢字庫，尋找到相應字元，輸出到 LCD 螢幕上。

HZK16重點摘要:

HZK16是符合GB23121UL 標準，每個漢字用16*16 BIT来表示，也就是說需要32個字元來顯示一個漢字
每個漢字由兩個字元編碼，範圍是 A1A1~FEFE，分為區碼和位碼，如圖a:
圖a所示每區有94個漢字，每區用32字元表示，所以所尋找漢字偏移量是: (94*(區碼-0xA1) +位碼-0xA1)*32

fig. a

實作:LCD上顯示中英字體

=====================================================================
show_font.c

#include <sys/mman.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <unistd.h>

#include <linux/fb.h>

#include <fcntl.h>

#include <stdio.h>

#include <string.h>

#define FONTDATAMAX 4096

static const unsigned char fontdata_8x16[FONTDATAMAX] = {

/* 0 0x00 '^@' */

0x00, /* 00000000 */

/* 1 0x01 '^A' */

0x00, /* 00000000 */

0x7e, /* 01111110 */

0x81, /* 10000001 */

0xa5, /* 10100101 */

0x81, /* 10000001 */

0xbd, /* 10111101 */

0x99, /* 10011001 */

0x81, /* 10000001 */

0x7e, /* 01111110 */

0x00, /* 00000000 */

/* 2 0x02 '^B' */

0x00, /* 00000000 */

0x7e, /* 01111110 */

0xff, /* 11111111 */

0xdb, /* 11011011 */

0xff, /* 11111111 */

0xc3, /* 11000011 */

0xe7, /* 11100111 */

0xff, /* 11111111 */

0x7e, /* 01111110 */

0x00, /* 00000000 */

.................................

/* 255 0xff '' */

0x00, /* 00000000 */

};

int fd_fb;

struct fb_var_screeninfo var;

struct fb_fix_screeninfo fix;

int screen_size;

unsigned char *fbmem;

unsigned int line_width;

unsigned int pixel_width;

unsigned char *hzkmem;

int fd_hzk16;

struct stat hzk_stat;

// display pixel

void lcd_put_pixel(int x, int y, unsigned int color)

{

unsigned char *pen_8 = fbmem+y*line_width+x*pixel_width;

unsigned short *pen_16;

unsigned int *pen_32;

unsigned int red, green, blue;

pen_16 = (unsigned short *)pen_8;

pen_32 = (unsigned int *)pen_8;

switch(var.bits_per_pixel)

{

case 8:

// 調色板

*pen_8 = color;

break;

case 16:

// 565

red = (color >> 16) & 0xff;

green = (color >> 8) & 0xff;

blue = (color >> 0) & 0xff;

color = ((red >> 3) << 11) | ((green >> 2) << 5) | (blue >> 3);

*pen_16 = color;

break;

case 32:

*pen_32 = color;

break;

default:

printf("can't surport %dbpp\n", var.bits_per_pixel);

break;

}

// input ascii

void lcd_put_ascii(int x, int y, unsigned char c)

{

unsigned char *dots = (unsigned char *)&fontdata_8x16[c*16];

int i,b;

unsigned char byte;

for(i=0; i<16; i++) // y axiel

{

byte = dots[i]; // 一個 i 表示一個 byte

for(b=7; b>=0; b--) // x axiel

{

if(byte & (1<<b))

{

lcd_put_pixel(x+7-b, y+i, 0xffffff);

}

else

{

lcd_put_pixel(x+7-b, y+i, 0);

}

// input 漢字

void lcd_put_chinese(int x, int y, unsigned char *str)

{

unsigned int area = str[0] - 0xA1; // HZK16 區碼第一個為空字元

unsigned int where = str[1] - 0xA1; // HZK16 位碼第一個為空字元

unsigned char *dots = hzkmem + (area * 94 + where)*32;

unsigned char byte;

int i, j, b;

for(i=0; i<16; i++)

{

for(j=0; j<2; j++) // y axiel

{

byte = dots[i*2+j]; // 一個 i or j 表示一個 byte

for(b=7; b>=0; b--) // x axiel

{

// show

if(byte & (1<<b))

{

lcd_put_pixel(x+j*8+7-b, y+i, 0xffffff);

}

else // hide

{

lcd_put_pixel(x+j*8+7-b, y+i, 0);

}

int main(int argc, char **argv)

{

unsigned char str[] = "中";

fd_fb = open("/dev/fb0", O_RDWR);

if(fd_fb < 0)

{

printf("can't open /dev/fb0\n");

return -1;

}

if(ioctl(fd_fb, FBIOGET_VSCREENINFO, &var))

{

printf("can't get var\n");

return -1;

}

// 這裡可以獲得LCD的可變參數

if(ioctl(fd_fb, FBIOGET_FSCREENINFO, &fix))

{

printf("can't get fix\n");

return -1;

}

line_width = var.xres * var.bits_per_pixel / 8; // Representative of the number of bytes per row

pixel_width = var.bits_per_pixel / 8; // Representative of the number of bytes per pixel

screen_size = var.xres * var.yres * var.bits_per_pixel / 8; // Representative of the number of bytes per frame

// 映射一塊顯存，第一個參數代表映射的位址，NULL表示自由分配

fbmem = (unsigned char *)mmap(NULL , screen_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd_fb, 0);

if(fbmem == (unsigned char *)-1)

{

printf("can't mmap\n");

return -1;

}

fd_hzk16 = open("HZK16", O_RDONLY);

if(fd_hzk16 < 0)

{

printf("can't open HZK16\n");

return -1;

}

// 獲取漢字庫文件的資訊，我們主要是為了獲得其大小

if(fstat(fd_hzk16, &hzk_stat))

{

printf("can't get fstat\n");

return -1;

}

// 為漢字庫映射一部分記憶體：這樣我們就可以像訪問陣列一樣來訪問漢字庫了

hzkmem = (unsigned char *)mmap(NULL , hzk_stat.st_size, PROT_READ, MAP_SHARED, fd_hzk16, 0);

if(hzkmem == (unsigned char *)-1)

{

printf("can't mmap for hzk16\n");

return -1;

}

// clear lcd screen

memset(fbmem, 0, screen_size);

lcd_put_ascii(var.xres/2, var.yres/2, 'A'); // display "A"

printf("chinese code: %02x %02x\n", str[0], str[1]); // print 0xXX of "中"

lcd_put_chinese(var.xres/2 + 8, var.yres/2,str); // display "中"

return 0;

}

===================================================================

測試:

1. 安裝 lcd driver

配置、修改内核支持把lcd.c编译进去

把驱动程序lcd.c拷贝到内核的drivers/video/目录下

修改drivers/video/Makefile
-----------------------
#obj-$(CONFIG_FB_S3C2410) += s3c2410fb.o
obj-$(CONFIG _FB_S3C2410) += lcd.o

------------------------

make menuconfig选择上对lcd的配置
Device Drivers --->

Graphics support --->

<*> Support for frame buffer devices --->

<*> S3C2410 LCD framebuffer support

make uImage

新kernel啟動

2. 編譯應用程式

$ arm-linux-gcc -o show_font show_font.c
./show_font

3. 結果
console 顯示如下:

/mnt/nfs # ./show_font

chinese code: d6 d0

JZ2440 開發版顯示如下:

參考資料:

嵌入式Linux應用開發完全手冊

韋東山視頻三期

http://wenku.baidu.com/view/170f49d049649b6648d7478e.html (hzk16 介紹)

http://wenku.baidu.com/view/0774d20c52ea551810a68768.html (hzk16範例)

Learning record

Wednesday, October 7, 2015

Character Bitmap display - 2

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