at91_usart.c

基于ARM7微控制器AT91X40开发板的定时器程序

/*   
 * at91_usart.c
 * 
 * author: Kexin ([e-mail]) Tel:[phone]
 * date:   2007-11-27	
 */
#include "at91_usart.h"

static volatile struct at91_usarts *usarts[AT91_USART_CNT] = {
	(volatile struct at91_usarts *) AT91_USART0_BASE,
	(volatile struct at91_usarts *) AT91_USART1_BASE
};

/*static unsigned long calc_CD(unsigned long baudrate)
{
	return (UART_CLOCK / baudrate);
}*/

static void usart_init(volatile struct at91_usarts *uart)
{
	/* Reset the USART */
	uart->cr = US_TXDIS | US_RXDIS | US_RSTTX | US_RSTRX;

	uart->rcr = 0;
	uart->tcr = 0;
	/* Set the serial port into a safe sane state */
	uart->mr = US_USMODE(0) | US_USCLKS(0) | US_CHRL(3) | US_NBSTOP(0) | US_PAR(5) | US_SYNC(0) | US_CLKO | US_CHMODE(0);

	uart->brgr = 213;//calc_CD(9600);//baudrate=MCK/(16*brgr) (mr over=0) OR baudrate=MCK/(8*brgr) (mr over=1)

	uart->rtor = 20;			     // timeout = value * 4 *bit period
	uart->ttgr = 0;				     // no guard time
	uart->rcr = 0;
	uart->rpr = 0;
	uart->tcr = 0;
	uart->tpr = 0;
}

void at91_init_usart(void)
{
	usart_init(usarts[0]);
}

static void usart_printf(volatile struct at91_usarts *uart, char p)
{
	uart->thr = p;
}

int printf(char *p)
{
	if(*p=='\0') return -1;
	while(*p!='\0')		usart_printf(usarts[0],*p++);

	return 1;
}