uart.c

S3C4510(ARM7)开发板bootloader实现及板载硬件测试代码

#include "uart.h"

int UART_BASE;
int uart_get;


void irq_handler(void);

void uart_init(unsigned channel, unsigned long baud)
{
	unsigned instruction;
	/* ARM irq exception vector addr is 0x00000018  */
	unsigned *irq_vec_addr = ( unsigned *) 0x18;
	/* this is isr entry address, could be another address like 0x3c, 0x58... */
	unsigned *isr_entry_addr = ( unsigned *) 0x58;
	*(unsigned *) (channel + UBRDIV) = baud;	
	*(unsigned *) (channel + ULCON) = (ULCR8bits);
		
	UART_BASE = channel;

	/* set the ISR entry at 0x58  */
	*isr_entry_addr = (unsigned)irq_handler;
	
	/* make an instruction: it is machine-code for "ldr  pc, [pc, #(58-18-8)]"  */
	instruction = ((unsigned) isr_entry_addr  - (unsigned)irq_vec_addr - 0x08) | 0xe59ff000;
	
	/* set this instruction at 0x18  */
	*irq_vec_addr = instruction;	
	
	// unmask the uart0 TX interrupt 
	INTMSK &= ~((1<<21) | (1 << 5) | (1 << 7));   

}

int uart_putchar(int ch)
{
	
	while ( TX_READY(GET_STATUS(UART_BASE))==0)
		;
	PUT_CHAR(UART_BASE, ch);
	
	return 0;
}

char uart_getchar(void)
{
	while ( (RX_DATA(GET_STATUS(UART_BASE)))==0 ) 
		;		
	return(GET_CHAR(UART_BASE));
}

int uart_puts(const char *str)
{
	int i;
	char ch;
	
	if (!str)
		return -1;
		
	for (i = 0; str[i] != '\0'; i++)
	{
		ch = str[i];
		
		while ( TX_READY(GET_STATUS(UART_BASE))==0)
			;
		PUT_CHAR(UART_BASE, ch);	
	}
	return 0;
}

static void uart0_irq_handler(void)
{
		while ( (RX_DATA(GET_STATUS(UART_BASE)))==0 )
			;		
		uart_get = GET_CHAR(UART_BASE);
						
		INTPND |= UART0_MASK;
}

static void uart1_irq_handler(void)
{
		while ( (RX_DATA(GET_STATUS(UART_BASE)))==0 )
			;		
		uart_get = GET_CHAR(UART_BASE);
						
		INTPND |= UART1_MASK;
}

void do_isr(void)
{
	void (*current_pc)(void) = 0;
	
	if (INTPND & UART0_MASK)
		current_pc = uart0_irq_handler;
		if (INTPND & UART1_MASK)
		current_pc = uart1_irq_handler;
	if (INTPND & INT0_MASK)
			current_pc = int0_irq_handler;
	if (INTPND & TIMER0_MASK)
		  current_pc = timer0_irq_handler;

	current_pc();	
}

void uart0demo( void )
{	
	uart_get = -(~0);
	uart_init(UART0_BASE, BAUD_19200);
	uart_puts("Now input any char to begin uart0 demo.\r\nThe char you input will echo on the host screen.\r\n");
	uart_puts("Press 'Enter' to quit\r\n");
	
	for (; ;)	
	{
		while (uart_get == -(~0))
			;
		if (uart_get == '\r' || uart_get == '\n')
			break;
		uart_putchar(uart_get);
		uart_get = -(~0);
	}
	 
	return;
}

void uart1demo( void )
{	
	uart_get = -(~0);
	uart_init(UART1_BASE, BAUD_19200);
	uart_puts("Now input any char to begin uart1 demo.\r\nThe char you input will echo on the host screen.\r\n");
	uart_puts("Press 'Enter' to quit\r\n");

	for (; ;)	
	{
		while (uart_get == -(~0))
			;
		if (uart_get == '\r' || uart_get == '\n')
			break;
		uart_putchar(uart_get);
		uart_get = -(~0);
	}
	 
	return;
}