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#include <serial.h>
#include "bindings.h"
// port numbers for first four serial ports
static uint16_t SERIAL_PORTS[] = {
[COM1] = 0x3F8,
[COM2] = 0x2F8,
[COM3] = 0x3E8,
[COM4] = 0x2E8,
};
// initialize the specified COM port for serial
// see https://wiki.osdev.org/Serial_Ports
// and https://en.wikibooks.org/wiki/Serial_Programming/8250_UART_Programming
int serial_init(enum serial_com_port com) {
uint16_t port = SERIAL_PORTS[com];
outb(port + 1, 0x00); // disable interrupts
outb(port + 3, 0x80); // enable DLAB (divisor latch access bit)
outb(port + 0, 0x03); // (lo) Set baud divisor to 3 38400 baud
outb(port + 1, 0x00); // (hi)
outb(port + 3, 0x03); // disable DLAB, set 8 bits per word, one stop bit, no parity
outb(port + 2, 0xC7); // enable and clear FIFOs, set to maximum threshold
// outb(port + 4, 0x0B); // TODO copied this from osdev wiki but i don't think you need it here
outb(port + 4, 0x1E); // set in loopback mode for test
outb(port + 0, 0xAE); // test by sending 0xAE
uint8_t response = inb(port + 0);
if(response != 0xAE) {
// TODO panic here?
return -1;
}
// disable loopback, enable IRQs
outb(port + 4, 0x0F);
return 0;
}
uint8_t serial_in(enum serial_com_port com) {
uint16_t port = SERIAL_PORTS[com];
// wait for data to be available
while((inb(port + 5) & 0x01) == 0);
return inb(port);
}
void serial_out(enum serial_com_port com, uint8_t ch) {
uint16_t port = SERIAL_PORTS[com];
// wait for output to be free
while((inb(port + 5) & 0x20) == 0);
outb(port, ch);
}
void serial_out_str(enum serial_com_port com, char *str) {
uint16_t port = SERIAL_PORTS[com];
for(; *str != '\0'; str++) {
while((inb(port + 5) & 0x20) == 0);
outb(port, *str);
}
}
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