main.c

UART developing tutorial module with source codes a褌胁 hints.

//  ****************************************************************************************************************
//   						main.c
// 
//		Interrupt-driven USART0 demonstration program for Olimex SAM7-EX256 Evaluation Board
//
//		Interrupt-driven simple demo reads 10 characters from USART0 (9600 baud, 8 data bits, 1 stop bit, no parity)
//		When 10 characters are read, they are transmitted back to the source.
//
//		This version uses DMA control of receive and transmit characters.
//      Using DMA, there are only two interrupts instead of twenty.
//
//		Use standard RS-232 serial cable and the Windows HyperTerm program to test.
//
//		Blinks LED (pin PA3) with an endless loop
//		PA3 is pin 1 on the EXT 20-pin connector (3.3v is pin 18)
//
//		The Olimex SAM7-EX256 board has no programmable LEDs. 
//		Added a simple test LED from Radio Shack as shown below (can be attached to the 20-pin EXT connector.)
//
//		    3.3 volts  |---------|           anode  |----|                PA3
//		    EXT O------| 470 ohm |------------------|LED |--------------O EXT
//          Pin 18     |---------|                  |----| cathode        pin 1
//                                              Radio Shack Red LED
//                                              276-026 T-1 size (anode is the longer wire)
//
//          LED current:  I = E/R  = 3.3/470  =  .007 amps = 7 ma
//			Note: most PIO pins can drive 8 ma on the AT91SAM7X256, so we're OK
//
//
//		
//		Author:  James P Lynch  June 22, 2008
//  ****************************************************************************************************************
 
//  *******************************************************
//                Header Files
//  *******************************************************
#include "AT91SAM7X256.h"
#include "board.h"


//  *******************************************************
//                External References
//  *******************************************************
extern	void LowLevelInit(void);
extern	void USART0Setup(void);
extern	unsigned enableIRQ(void);


int	main (void) {
	
	unsigned long	j;
	unsigned int	IdleCount = 0;
	
	// Initialize the Atmel AT91SAM7S256 (watchdog, PLL clock, default interrupts, etc.)
	LowLevelInit();

	// Set up the LED (PA3)
	volatile AT91PS_PIO	pPIO = AT91C_BASE_PIOA;			// pointer to PIO data structure
	pPIO->PIO_PER = LED_MASK;							// PIO Enable Register - allow PIO to control pin PP3
	pPIO->PIO_OER = LED_MASK;							// PIO Output Enable Register - sets pin P3 to outputs
	pPIO->PIO_SODR = LED_MASK;							// PIO Set Output Data Register - turns off the LED
	
	// set up USART0
	USART0Setup();

	// enable interrupts
	enableIRQ();

	// *****************************
	// *  endless blink loop       *
	// *****************************
	while (1) {
		if  ((pPIO->PIO_ODSR & LED4) == LED4)			// read previous state of LED4
			pPIO->PIO_CODR = LED4;						// turn LED4 (DS1) on	
		else
			pPIO->PIO_SODR = LED4;						// turn LED4 (DS1) off
		
		for (j = 1000000; j != 0; j-- );				// wait 1 second 1000000
	
		IdleCount++;									// count # of times through the idle loop
	}
}