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