开源的国外AT91SAM7S64开发板

				//usart.c
				#include "usart.h"
				#include "AT91SAM7S64.h"
				
				// Pointers
				AT91PS_PIO    u_pPio    = AT91C_BASE_PIOA;
				AT91PS_PMC    u_pPMC    = AT91C_BASE_PMC;
				AT91PS_USART  u_pUSART0 = AT91C_BASE_US0;
				AT91PS_USART  u_pUSART1 = AT91C_BASE_US1;
				AT91PS_PDC    u_pPDC0   = AT91C_BASE_PDC_US0;
				AT91PS_PDC    u_pPDC1   = AT91C_BASE_PDC_US1;
				AT91PS_MC     u_pMC     = AT91C_BASE_MC;
				AT91PS_AIC    u_pAic    = AT91C_BASE_AIC;
				
				void InitUSART0(void)
				{
				
				  u_pPio->PIO_PDR = BIT5 | BIT6 | BIT21 | BIT22; //Disables the PIO from controlling the corresponding pin (enables peripheral control of the pin).
				  u_pPio->PIO_ASR = BIT5 | BIT6 | BIT21 | BIT22; //Assigns the I/O line to the Peripheral A function.
				  u_pPio->PIO_BSR = 0;                           //Assigns the I/O line to the Peripheral B function.
				
				
				  //enable the clock of USART
				  u_pPMC->PMC_PCER = 1				
				  //set baud rate divisor register
				  u_pUSART0->US_BRGR = 313; //((48000000)/9600x16)
				
				  //write the Timeguard Register
				  u_pUSART0->US_TTGR = 0;
				
				  //Set the USART mode
				  u_pUSART0->US_MR = 0x08c0;
				
				  //Enable the RX and TX PDC transfer requests
				  u_pPDC0->PDC_PTCR = AT91C_PDC_TXTEN | AT91C_PDC_RXTEN;
				
				  //Enable usart
				  u_pUSART0->US_CR = 0x50;
				
				}
				
				void InitUSART1(void)
				{
				
				  u_pPio->PIO_PDR = BIT5 | BIT6 | BIT21 | BIT22; //Disables the PIO from controlling the corresponding pin (enables peripheral control of the pin).
				  u_pPio->PIO_ASR = BIT5 | BIT6 | BIT21 | BIT22; //Assigns the I/O line to the Peripheral A function.
				  u_pPio->PIO_BSR = 0;                           //Assigns the I/O line to the Peripheral B function.
				
				
				  //enable the clock of USART
				  u_pPMC->PMC_PCER = 1				
				  //set baud rate divisor register
				  u_pUSART1->US_BRGR = 313; //((48000000)/9600x16)
				
				  //write the Timeguard Register
				  u_pUSART1->US_TTGR = 0;
				
				  //Set the USART mode
				  u_pUSART1->US_MR = 0x08c0;
				
				  //Enable the RX and TX PDC transfer requests
				  u_pPDC1->PDC_PTCR = AT91C_PDC_TXTEN | AT91C_PDC_RXTEN;
				
				  //Enable usart
				  u_pUSART1->US_CR = 0x50;
				
				}
				
				//write char to UART0
				void write_char_USART0(unsigned char ch)
				{
				  while (!(u_pUSART0->US_CSR&AT91C_US_TXRDY)==1);
				  u_pUSART0->US_THR = ((ch & 0x1FF));
				}
				
				//read char from UART0
				unsigned char read_char_USART0(void)
				{
				  while (!(u_pUSART0->US_CSR&AT91C_US_RXRDY)==1);
				  return((u_pUSART0->US_RHR) & 0x1FF);
				}
				
				//write char from UART0 (non stop)
				unsigned char read_char_USART0_nonstop(void)
				{
				  if((u_pUSART0->US_CSR&AT91C_US_RXRDY)==1)
				    return((u_pUSART0->US_RHR) & 0x1FF);
				  else return 0;
				}
				
				//write char to UART1
				void write_char_USART1(unsigned char ch)
				{
				  while (!(u_pUSART1->US_CSR&AT91C_US_TXRDY)==1);
				  u_pUSART1->US_THR = ((ch & 0x1FF));
				}
				
				//read char from UART1
				unsigned char read_char_USART1(void)
				{
				  while (!(u_pUSART1->US_CSR&AT91C_US_RXRDY)==1);
				  return((u_pUSART1->US_RHR) & 0x1FF);
				}
				
				//read char from UART1 (non stop)
				unsigned char read_char_USART1_nonstop(void)
				{
				  if ((u_pUSART1->US_CSR&AT91C_US_RXRDY)==1)
				    return((u_pUSART1->US_RHR) & 0x1FF);
				  else
				    return 0;
				}
				
				
				void write_str_USART0(unsigned char* buff) {
				
				  unsigned int i = 0x0;
				
				  while(buff[i] != '\0') {
				    write_char_USART0(buff[i]);
				    i++;
				  }
				
				}
				
				
				void write_str_USART1(unsigned char* buff) {
				
				  unsigned int i = 0x0;
				
				  while(buff[i] != '\0') {
				    write_char_USART1(buff[i]);
				    i++;
				  }
				}