driver/serial.c


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#include "driver/serial.h"

#include "asm_x86.h" // provides x86_inb() and x86_outb()

/** COM1 Port */
static const PORT=0x3f8;

void serial_init()
{
   x86_outb(PORT + 1, 0x00);    // Disable all interrupts
   x86_outb(PORT + 3, 0x80);    // Enable DLAB (set baud rate divisor)
   x86_outb(PORT + 0, 0x03);    // Set divisor to 3 (lo byte) 38400 baud
   x86_outb(PORT + 1, 0x00);    //                  (hi byte)
   x86_outb(PORT + 3, 0x03);    // 8 bits, no parity, one stop bit
   x86_outb(PORT + 2, 0xC7);    // Enable FIFO, clear them, with 14-byte threshold
   x86_outb(PORT + 4, 0x0B);    // IRQs enabled, RTS/DSR set
}

static uint32_t serial_received()
{
   return x86_inb(PORT + 5) & 1;
}
 
uint8_t serial_read()
{
   while (serial_received() == 0);
   return x86_inb(PORT);
}

static uint32_t is_transmit_empty()
{
   return x86_inb(PORT + 5) & 0x20;
}
 
void serial_write(uint8_t a)
{
   while (is_transmit_empty() == 0);
   x86_outb(PORT,a);
}