Driving and Displaying on an LCD Screen Using GPIO — mini2440

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Objective: LCD screen driving and display.

Understand GPIO control methods and independently write a simple menu test program (including display of colored Chinese characters and static graphics).

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1. Terminology Q&A

1. What is a GPIO port? What related resources are available on the mini2440?

Answer:

2. Chip documentation (data sheet interpretation) for GPIO ports on S3C2416/S3C2440

2. Source Code Analysis

1. sys/ioctl.h

2. IOR, IOW

3. Identify the code architecture and its meaning.

4. Purpose of #include <afxext.h>

Answer:

Defines MFC extensions and related classes, including:  
// Classes declared in this file  
//CObject  
//CCmdTarget;  
//CWnd  
//CButton  
class CBitmapButton;    // Bitmap button (self-draw)  
class CControlBar;      // control bar  
class CStatusBar;       // status bar  
class CToolBar;         // toolbar  
class CDialogBar;       // dialog as control bar  
class CReBar;           // ie40 dock bar  
class CSplitterWnd;     // splitter manager  
//CView  
//CScrollView  
class CFormView;        // view with a dialog template  
class CEditView;        // simple text editor view  
//CDC  
class CMetaFileDC;      // a metafile with proxy  
class CRectTracker;     // tracker for rectangle objects

5. Usage of extern variables

extern can be placed before a variable or function to indicate that its definition resides in another file, instructing the compiler to look for the definition in other modules when encountering such variables or functions.
Additionally, extern can also be used for linkage specification.

3. LCD Driver Analysis

1. mmap((void*)target, length, PROT_READ|PROT_WRITE, MAP_SHARED, fd, target)
   // Detailed explanation of parameters? Especially target

2. volatile BYTE *lcdcmdadr
   // What does this mean?

void Xadd(char startx,char endx){  
    LCDCOM_MASTER(0x2A);             // Understand the meaning of these addresses  
    LCDDATA_MASTER(startx);  
    LCDDATA_MASTER(endx);  
}

// Map user space memory address to kernel space memory address  
lcdcmdadr = (BYTE *)mapDirectIoRegister(LCD_COMMAND, MAP_SIZE);

LCD_RST_LOW;    usleep(100000);  
LCD_RST_HIG;    usleep(100000);     // Simulate a square wave  
LCD_ON;