50 lines
1.5 KiB
C
50 lines
1.5 KiB
C
#include "serial.h"
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#define PORT 0x3f8 // COM1
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static inline void outb(unsigned short port, unsigned char val) {
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asm volatile ("outb %0, %1" : : "a"(val), "Nd"(port) : "memory");
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}
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static inline unsigned char inb(unsigned short port) {
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unsigned char ret;
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asm volatile("inb %1, %0" : "=a"(ret) : "Nd"(port) : "memory");
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return ret;
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}
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int serial_init() {
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outb(PORT + 1, 0x00); // Disable all interrupts
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outb(PORT + 3, 0x80); // Enable DLAB (set baud rate divisor)
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outb(PORT + 0, 0x03); // Set divisor to 3 (lo byte) 38400 baud
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outb(PORT + 1, 0x00); // (hi byte)
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outb(PORT + 3, 0x03); // 8 bits, no parity, one stop bit
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outb(PORT + 2, 0xC7); // Enable FIFO, clear them, with 14-byte threshold
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outb(PORT + 4, 0x0B); // IRQs enabled, RTS/DSR set
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outb(PORT + 4, 0x1E); // Set in loopback mode, test the serial chip
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outb(PORT + 0, 0xAE); // Test serial chip (send byte 0xAE and check if serial
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// returns same byte)
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// Check if serial is faulty (i.e: not same byte as sent)
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if (inb(PORT + 0) != 0xAE) {
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return 1;
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}
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// If serial is not faulty set it in normal operation mode
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// (not-loopback with IRQs enabled and OUT#1 and OUT#2 bits enabled)
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outb(PORT + 4, 0x0F);
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return 0;
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}
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static int serial_is_transmit_empty() { return inb(PORT + 5) & 0x20; }
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static void serial_write_char(char chr) {
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while (serial_is_transmit_empty() == 0);
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outb(PORT, chr);
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}
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void serial_write_string(const char* text) {
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int i = 0;
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while(text[i]) {
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serial_write_char(text[i]);
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i++;
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}
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}
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