main.c

Atmel 公司提供的另一个参考代码

//  *****************************************************************************
//   						main.c
// 
//     Demonstration program for Atmel AT91SAM7S256-EK Evaluation Board
//
//     blinks LED0 (pin PA0) with an endless loop
//     blinks LED1 (pin PA1) using timer0 interrupt (200 msec rate)
//	   switch SW1 (PA19) triggers FIQ interrupt, turns on LED2 (Pin PA2)
//     plenty of variables for debugger practice
//
//  Author:  James P Lynch  May 12, 2007
//  *****************************************************************************
 
//  *******************************************************
//                Header Files
//  *******************************************************
#include "AT91SAM7S256.h"
#include "board.h"
#include "math.h"
#include "stdlib.h"
#include "string.h"

//  *******************************************************
//                Function Prototypes
//  *******************************************************
void Timer0IrqHandler(void);
void FiqHandler(void);

//  *******************************************************
//                External References
//  *******************************************************
extern	void LowLevelInit(void);
extern	void TimerSetup(void);
extern	unsigned enableIRQ(void);
extern	unsigned enableFIQ(void);

//  *******************************************************
//               Global Variables
//  *******************************************************
unsigned int	FiqCount = 0;		// global uninitialized variable		
int				q;					// global uninitialized variable
int				r;					// global uninitialized variable
int				s;					// global uninitialized variable
int				m = 2;				// global initialized variable
int				n = 3;				// global initialized variable
int				o = 6;				// global initialized variable

struct comms {
	int		nBytes;
	char	*pBuf;
	char	Buffer[32];
}  Channel = {5, &Channel.Buffer[0], {"Faster than a speeding bullet"}};

int	main (void) {
	
	// lots of variables for debugging practice
	int				a, b, c;							// uninitialized variables
	char			d;									// uninitialized variable
	int				w = 1;								// initialized variable
	int				k = 2;								// initialized variable
	static long		x = 5;								// static initialized variable
	static char		y = 0x04;							// static initialized variable
	const char		*pText = "The rain in Spain";		// initialized string pointer variable
	struct EntryLock {									// initialized structure variable
		long		Key;
		int			nAccesses;
		char		Name[17];
	}  Access = {14705, 0, "Sophie Marceau"};		
	unsigned long	j;									// loop counter (stack variable)
	unsigned long	IdleCount = 0;						// idle loop blink counter (2x)
	int				*p;									// pointer to 32-bit word
	typedef void 	(*FnPtr)(void);						// create a "pointer to function" type
	FnPtr 			pFnPtr;								// pointer to a function
	double			x5;									// variable to test library function
	double			y5 = -172.451;						// variable to test library function
	const char 		DigitBuffer[] = "16383";			// variable to test library function
	long			n;									// variable to test library function
	
	// Initialize the Atmel AT91SAM7S256 (watchdog, PLL clock, default interrupts, etc.)
	LowLevelInit();
	

	// enable the Timer0 peripheral clock
	volatile AT91PS_PMC	pPMC = AT91C_BASE_PMC;			// pointer to PMC data structure
	pPMC->PMC_PCER = (1<<AT91C_ID_TC0);					// enable Timer0 peripheral clock


	// Set up the LEDs (PA0 - PA3)
	volatile AT91PS_PIO	pPIO = AT91C_BASE_PIOA;			// pointer to PIO data structure
	pPIO->PIO_PER = LED_MASK | SW1_MASK;				// PIO Enable Register - allow PIO to control pins P0 - P3 and pin 19
	pPIO->PIO_OER = LED_MASK;							// PIO Output Enable Register - sets pins P0 - P3 to outputs
	pPIO->PIO_SODR = LED_MASK;							// PIO Set Output Data Register - turns off the four LEDs
	

	// Select PA19 (pushbutton) to be FIQ function (Peripheral B)
	pPIO->PIO_BSR = SW1_MASK;
	

	// Set up the AIC  registers for Timer 0  
	volatile AT91PS_AIC	pAIC = AT91C_BASE_AIC;			// pointer to AIC data structure
	pAIC->AIC_IDCR = (1<<AT91C_ID_TC0);					// Disable timer 0 interrupt in AIC Interrupt Disable Command Register			
	pAIC->AIC_SVR[AT91C_ID_TC0] =						// Set the TC0 IRQ handler address in AIC Source 
    	(unsigned int)Timer0IrqHandler;        			// Vector Register[12]
	pAIC->AIC_SMR[AT91C_ID_TC0] =						// Set the interrupt source type and priority 
   		(AT91C_AIC_SRCTYPE_INT_HIGH_LEVEL | 0x4 ); 		// in AIC Source Mode Register[12]
	pAIC->AIC_ICCR = (1<<AT91C_ID_TC0); 				// Clear the TC0 interrupt in AIC Interrupt Clear Command Register
	pAIC->AIC_IDCR = (0<<AT91C_ID_TC0);					// Remove disable timer 0 interrupt in AIC Interrupt Disable Command Reg			
	pAIC->AIC_IECR = (1<<AT91C_ID_TC0); 				// Enable the TC0 interrupt in AIC Interrupt Enable Command Register
	
	// Set up the AIC registers for FIQ (pushbutton SW1)
	pAIC->AIC_IDCR = (1<<AT91C_ID_FIQ);					// Disable FIQ interrupt in AIC Interrupt Disable Command Register			
	pAIC->AIC_SMR[AT91C_ID_FIQ] =						// Set the interrupt source type in AIC Source 
    	(AT91C_AIC_SRCTYPE_INT_POSITIVE_EDGE);  		// Mode Register[0]
	pAIC->AIC_ICCR = (1<<AT91C_ID_FIQ); 				// Clear the FIQ interrupt in AIC Interrupt Clear Command Register
	pAIC->AIC_IDCR = (0<<AT91C_ID_FIQ);					// Remove disable FIQ interrupt in AIC Interrupt Disable Command Register			
	pAIC->AIC_IECR = (1<<AT91C_ID_FIQ); 				// Enable the FIQ interrupt in AIC Interrupt Enable Command Register
	

	// Three functions from the libraries
	a = strlen(pText);									// strlen( ) returns length of a string
	x5 = fabs(y5);										// fabs( ) returns absolute value of a double
	n = atol(DigitBuffer);								// atol( ) converts string to a long
	

	// Setup timer0 to generate a 10 msec periodic interrupt
	TimerSetup();

	// enable interrupts
	enableIRQ();
	enableFIQ();

	// endless blink loop
	while (1) {
		if  ((pPIO->PIO_ODSR & LED1) == LED1)			// read previous state of LED1
			pPIO->PIO_CODR = LED1;						// turn LED1 (DS1) on	
		else
			pPIO->PIO_SODR = LED1;						// turn LED1 (DS1) off
		
		for (j = 1000000; j != 0; j-- );				// wait 1 second 1000000
	
		IdleCount++;									// count # of times through the idle loop
		pPIO->PIO_SODR = LED3;							// turn LED3 (DS3) off
											
		// uncomment following four lines to cause a data abort(3 blink code)
		//if  (IdleCount >= 10) {						// let it blink 5 times then crash
		//	p = (int *)0x800000;						// this address doesn't exist
		//	*p = 1234;									// attempt to write data to invalid address
		//}
		
		// uncomment following four lines to cause a prefetch abort (two blinks)
		//if  (IdleCount >= 10) {						// let it blink 5 times then crash
		//	pFnPtr = (FnPtr)0x800000;					// this address doesn't exist
		//	pFnPtr();									// attempt to call a function at a illegal address
		//}
	}
}