! Startup.nxc

/**
 * LockCode 1.0.2
 *
 * Rename to "! Startup.nxc" and download to protect your NXT at startup.
 * When NXT is turned on it will prompt for a code.
 * The first time the program is run it will ask you to set a code.
 * If you enter the wrong code, the NXT will flash a message, otherwise,
 * the program will end, allowing you to access your NXT.
 * The dark grey button will turn off the NXT instead of ending the program.
 * If you forget the code and want to set a new one, simply delete the file
 * 'LockCode.dat' from the NXT using something like NeXT Explorer or NeXT Commander.
 * 
 * Created by 'bungeshea' on 10th October 2012
 * The NXT Generation Robotics - http://robotics.bungeshea.com
 */

#define FILE        	"LockCode.dat"	// Name of the file to store the code in
#define FILESIZE    	8

#define CLEAR_SCREEN	DRAW_OPT_CLEAR_WHOLE_SCREEN

/* Define the LockCode data type. It will hold four chars */
struct LockCode{
	char a;
	char b;
	char c;
	char d;
};

LockCode code;

/**
 * This function allows the user to
 * enter single number using the NXT buttons
 *
 * @return int value
 */
int GetNum(int x, int y = LCD_LINE5, int value = 0) {
	while(!ButtonPressed(BTNCENTER,0))	// Poll for button presses until the center button is pressed
	{
		NumOut(x, y, value); // Draw the number on the screen
		RectOut(x-3, y-2, 10, 12); // Draw a rectangle around the number
		if(ButtonPressed(BTNRIGHT,0)) // If the user presses the right arrow...
		{
			while(ButtonPressed(BTNRIGHT,0)); // Wait for the button to be released
			value++; // Increase the value
		}
		if(ButtonPressed(BTNLEFT,0)) // If the user presses the left arrow...
		{
			while(ButtonPressed(BTNLEFT,0)); // Wait for the button to be released
			value--; // Decrease the value
		}
		if (value < 0) value = 9; // If the value is below 0, set it to 9
		if (value > 9) value = 0; // If the value is above 9, set it to 0
	}
	while(ButtonPressed(BTNCENTER,0));	// Wait for the center button to be released
	RectOut(x-3, y-2, 10, 12, DRAW_OPT_CLEAR);	// Clear the rectangle
	return value;
}

/**
 * This function allows the user to
 * enter a four-digit passcode
 * using the NXT buttons
 *
 * @return LockCode code
 */
LockCode GetCode()
{
	LockCode code;
	// Draw placeholder numbers on the screen
	NumOut(15, LCD_LINE5, 0);
	NumOut(35, LCD_LINE5, 0);
	NumOut(55, LCD_LINE5, 0);
	NumOut(75, LCD_LINE5, 0);
	// Prompt the user for each digit of the code
	code.a = GetNum(15);
	code.b = GetNum(35);
	code.c = GetNum(55);
	code.d = GetNum(75);
	return code;
}

/**
 * This method will write the
 * code variable to the NXT's memory
 */
void WriteCode()
{
	byte handle; unsigned int result, fsize;
	DeleteFile(FILE);	// Delete the existing file
	CreateFile(FILE, FILESIZE, handle);	// Create a new file
	Write(handle, code);	// Write the code to the file
	CloseFile(handle);	// Close the file
}

/**
 * This method will read the passcode
 * from the NXT's internal memory and store it
 * in a LockCode varaible.
 */
void ReadCode()
{
	byte handle; unsigned int result, fsize;
	result = OpenFileRead(FILE, fsize, handle);	// Attempt to open the file
	if(result == LDR_SUCCESS) // If file exists...
	{
		Read(handle, code);	// Read the data to the Code variable
		CloseFile(handle);	// And close the file
	}
	else // If the file does not exist, prompt to create a new code
	{
		TextOut(12, LCD_LINE2, "Set passcode:", CLEAR_SCREEN);	// Show a message
		code = GetCode(); // Prompt the user to enter a new code
		WriteCode(); // Store the code in a file
	}
}

/**
 * This task will stop the dark grey button
 * from stopping the program, and instead
 * use it to turn off the NXT
 */
task turnOff()
{
	// only pass this point if the NXT is running the enhanced firmware
	#ifdef __ENHANCED_FIRMWARE__
	
 	SetAbortFlag(BTNSTATE_NONE); // disable the exit button
 	Wait(SEC_10); // wait 10 seconds to prevent the NXT from locking up
	while(true)
	{
		if(ButtonPressed(BTNEXIT, 0)) // if the exit button is pressed...
			ForceOff(true); // turn off the NXT
	}
	
	#endif
}

/**
 * This task will handle the actual entering and validating
 * the code part of our program, and display the on-screen prompts
 */
task lockCode()
{
	ReadCode(); // read the code stored in the NXT's memory
	while(true) // keep on prompting the user to enter a code
	{
		// show a message
		TextOut(7, LCD_LINE2, "Enter passcode:", CLEAR_SCREEN);
		// wait a bit to prevent accidental button presses
		Wait(10);
		// prompt the user to enter a code
		LockCode input = GetCode();
		// If the code that we've just entered matches the one stored on file...
		if(input == code) {
			Stop(true); // stop the program, allowing the user to access the NXT
		}
		else {
			// Else, flash some text and try again
			TextOut(7, LCD_LINE2, "Wrong passcode!");
			Wait(1500);
		}
	}
}

/**
 * The main task for our program
 * This will run when the program starts.
 * It will play a startup sound file at the volume
 * specified in the Settings menu on the NXT
 * and then start the lockCode and turnOff tasks
 */
task main()
{
	PlayFileEx("! Startup.rso", Volume(), 0);	// Play the startup sound
	Precedes(turnOff, lockCode);
}