Added support for setting up a serial port. This first serial driver appears to only work correctly in QEMU.

.gitignore

@@ -4,3 +4,4 @@
 *.iso
 *.bin
 *.ini
+*.out

Makefile

@@ -30,7 +30,7 @@ kernel.iso: kernel.o
 	grub-mkrescue --output=kernel.iso iso
 	
 qemu: kernel.iso
-	qemu-system-x86_64 -m 256M -cdrom kernel.iso &
+	qemu-system-x86_64 -serial stdio -m 256M -cdrom kernel.iso
 
 .PHONY: clean
 clean:

build_numbers.c

@@ -1,3 +1,3 @@
 #ifndef KERNEL_VERSION_NUMBER
-#define KERNEL_VERSION_NUMBER "0.0.1-293"
+#define KERNEL_VERSION_NUMBER "0.0.1-333"
 #endif

includes/io.h

@@ -1,4 +1,5 @@
 #ifndef IO_H
 #define IO_H
 void outb(unsigned short port, unsigned char data);
+unsigned char inb(unsigned short port);
 #endif

includes/kernel.h

@@ -1,9 +1,5 @@
 #ifndef KERNEL_H
 #define KERNEL_H
 
-void write_screen(unsigned int, char, unsigned char, unsigned char);
-void move(unsigned short);
-void draw_s(char*, unsigned char, unsigned char);
 int strlen(char*);
-void clear_screen(void);
 #endif

includes/serial.h

@@ -0,0 +1,23 @@
+#ifndef SERIAL_H
+#define SERIAL_H
+/* All the I/O ports are calculated relative to the data port. This is
+   because all serial ports have their ports in the same order but they
+   start at different values.
+*/
+
+#define COM1_PORT 						0x3F8
+
+#define SERIAL_DATA_PORT(base)			(base)
+#define SERIAL_FIFO_COMMAND_PORT(base) 	(base + 2)
+#define SERIAL_LINE_COMMAND_PORT(base) 	(base + 3)
+#define SERIAL_MODEM_COMMAND_PORT(base) (base + 4)
+#define SERIAL_LINE_STATUS_PORT(base) 	(base + 5)
+
+// Tells the serial port to expect the highest 8 bits on the data port first,
+// followed by the lowest 8 bits.
+#define SERIAL_LINE_ENABLE_DLAB 		0x80
+
+void set_serial_baud_rate(unsigned short, unsigned short);
+void configure_serial_line(unsigned short);
+int serial_transmit_fifo_empty(unsigned int);
+#endif

kernel/io.s

@@ -9,3 +9,13 @@ outb:
 	mov dx, [esp + 4] ; Move the address of the I/O port into the DX register
 	out dx, al		  ; Send the data to the I/O port
 	ret				  ; Return
+	
+global inb
+
+; inb - Returns a byte from the give I/O port.
+; stack: [esp + 4] The address of the I/O port
+;		 [esp    ] The return address
+inb:
+	mov dx, [esp + 4] 	; Move the address of the I/O port to the dx register.
+	in al, dx 			; Read a byte from the I/O port and store it in the al register
+	ret

kernel/kmain.c

@@ -1,10 +1,16 @@
 #include "../includes/io.h"
+#include "../includes/serial.h"
 #include "../includes/screen.h"
 
 void kmain()
 {
+	set_serial_baud_rate(COM1_PORT, 0x03);
+	configure_serial_line(COM1_PORT);
+	write_to_com(COM1_PORT, "Info From Kernel: Set up COM1 for messaging.\n");
 	clear_screen();
+	write_to_com(COM1_PORT, "Info From Kernel: Clearing screen.\n");
 	print_banner();
+	write_to_com(COM1_PORT, "Info From Kernel: Displaying OS banner.\n");
 	//draw_rect(20, 5, 50, 7, 0x4, 0xF);
 	draw_rect(0, 5, 5, 13, 0xF, 0x4);
 	draw_rect(5, 8, 10, 10, 0x4, 0xF);
@@ -14,11 +20,13 @@ void kmain()
 	set_cursor(0, 14);
 	move_cursor(0, 14);
 	move_cursor(0, 15);
-	draw_s("Test print", 0x8, 0xF);
+	draw_string("Test print", 0x8, 0xF);
 	move_cursor(0, 16);
-	draw_s("And now the cursor has been moved to y = 16.", 0x1, 0xF);
+	draw_string("And now the cursor has been moved to y = 16.", 0x1, 0xF);
 	move_cursor(5, 20);
-	draw_s("Cursor moved over 5 cells and down 4 cells.", 0xF, 0x0);
+	draw_string("Cursor moved over 5 cells and down 4 cells.", 0xF, 0x0);
+	draw_string("And the cursor moves to the end of the string", 0x1, 0xF);
+	draw_string("Now this string should have a newline now:\nAnd now a new line is here.", 0xF, 0x0);
 	//draw_rect(20, 5, 50, 7, 0x4, 0xF);
 	//draw_rect(20, 5, 50, 7, 0x4, 0xF);
 	//draw_rect(20, 5, 50, 7, 0x4, 0xF);
@@ -28,19 +36,3 @@ void kmain()
 	//draw_s("And 2nd Row. Now the 3rd row.", 2, 9);
 	asm("hlt");
 }
-
-void write_screen(unsigned int i, char c, unsigned char fg, unsigned char bg)
-{
-	char *fb = (char *) 0x000B8000;
-	fb[i] = c;
-	fb[i + 1] = ((fg & 0x0F) << 4) | (bg & 0x0F);
-}
-
-void move(unsigned short pos)
-{
-	
-	outb(0x3D4, 14);
-	outb(0x3D5, ((pos >> 8 ) & 0x00FF));
-	outb(0x3D4, 15);
-	outb(0x3D5, pos & 0x00FF);
-}

kernel/screen.c

@@ -62,11 +62,12 @@ void draw_rect(int start_x, int start_y, int end_x, int end_y, unsigned char fg,
 	}
 }
 
-void draw_s(char* string, unsigned char fg, unsigned char bg)
+void draw_string(char* string, unsigned char fg, unsigned char bg)
 {
 	unsigned short *video_buffer = 0x000B8000;
 	int attr = ((bg << 4) | (fg & 0x0F));
-	for(int i = 0; i < strlen(string); i++)
+	int length = strlen(string);
+	for(int i = 0; i < length; i++)
 	{
 		unsigned char current_char = string[i];
 		unsigned short *where = (unsigned short *) video_buffer + (cursor_y * 80) + i + cursor_x;
@@ -78,6 +79,8 @@ void draw_s(char* string, unsigned char fg, unsigned char bg)
 		
 		*where = string[i] | attr << 8;
 	}
+	
+	cursor_x = cursor_x + length + 1;
 }
 
 void set_cursor(unsigned char x, unsigned char y){

kernel/serial.c

@@ -0,0 +1,59 @@
+#include "../includes/io.h"
+/* Sets the speed of the data being sent. The default speed of a serial port
+   is 115,200 bits/s. The argument is a divisor of that number, hence the resulting
+   speed becomes 115,200 / divisor bits/s.
+*/
+void set_serial_baud_rate(unsigned short com, unsigned short divisor){
+	outb(com + 3, 0x80);//SERIAL_LINE_ENABLE_DLAB);
+	
+	outb(com, (divisor >> 8) & 0x00FF);
+	
+	outb(com, divisor & 0x00FF);
+}
+
+void configure_serial_line(unsigned short com){
+
+	// Configuring the Line
+	/* d: 		Enables (1) or disables (0) DLAB
+	   b: 		Break if controls is enabled (1)
+	   parity: 	The number of parity bits to use
+	   s: 		The number of stop bits to use (0 = One Stop, 1 = 1.5 or 2 stops)
+	   dl: 		Describes the langth of the data
+	   
+	   Bit:		| 7 | 6 | 5 4 3 | 2 | 1 0 |
+	   Content: | d | b | parity| s | dl  |
+	   Value:	| 0 | 0 | 0 0 0 | 0 | 1 1 | = 0x03
+	*/
+	outb(com + 3, 0x03);
+	// Configuring the Buffers
+	/* lvl: How many bytes should be stored in the FIFO buffers
+	   bs: 	If the buffers should be 16 or 64 bytes large
+	   r:	Reserved
+	   dma:	How the serial port data should be accessed
+	   clt: Clear the transmission FIFO buffer
+	   clr: Clear the reciever FIFO buffer
+	   e:	If the FIFO bufffer should be enabled or not
+	   
+	   Bit:		| 7 6 | 5 | 4 | 3  | 2  | 1  | 0 |
+	   Content:	| lvl | bs| r | dma| clt| clr| e |
+	   Value: 	| 1 1 | 0 | 0 | 0  | 1  | 1  | 1 |
+	*/
+	outb(com + 2, 0xC7);	
+	// Confirgure the Modem
+	outb(com + 4, 0x03);
+}
+/* @return 0 if the FIFO is not empty
+		   1 if the FIFO is empty
+*/
+int serial_transmit_fifo_empty(unsigned int com){
+	// 0x20 = 0010 0000
+	return inb((com + 5) & 0x20);
+}
+
+void write_to_com(unsigned int com, char* msg){
+	for(int i = 0; msg[i] != '\0'; i++){
+		while(serial_transmit_fifo_empty(com) == 0);
+		
+		outb(com, (char) msg[i]);
+	}
+}

support_files/boch.txt

@@ -7,3 +7,4 @@ boot: cdrom
 log: bochs.log
 clock: sync=realtime, time0=local
 cpu: count=1, ips=1000000
+com1: enabled=1, mode=file, dev=com1.out