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Posted: **Mon Jul 06, 2020 3:06 pm**

My keyboard handler and my translation table seem to be wrong.. It keeps typing multiple characters and the 'enter/return' key is mapped to '9' on the keyboard not sure how to proceed. I have two questions so here they are. How do you build a complete keyboard translation table? Why does the handler for the keyboard not responding properly (as far as only typing one character at a time etc.)?

Edit: I found Translation Sets
But how do I write one of those sets, I do NOT understand them. The keys and what not aren't in any particular order. They are just listed.

Here's the code: boot32-barebones
Note: The keyboard handler code is in kernel/drivers/keyboard.c. Along with the translation table.
Thanks in advance for all possible answer(s).

Posted: **Mon Jul 06, 2020 3:19 pm**

You're only handling key-down scan codes. There are also key-up scan codes.

Some scan codes are more than one byte long, but you can only receive one byte at a time. Your IRQ handler will need to keep track of when it receives the first byte of a multi-byte scan code in order to correctly respond to the subsequent byte(s).

It's a good idea to separate the "keyboard" and "keyboard controller" drivers. However, since most keyboards are USB nowadays, I wouldn't worry too much about that until after you have working USB drivers.

Posted: **Mon Jul 06, 2020 3:31 pm**

How do I handle key up and down events?

kernel/drivers/keyboard.c:

Code: Select all

/*
 * keyboard.c - Source file for simple keyboard input.
 *
 * Author: Philip R. Simonson
 * Date  : 07/04/2020
 *
 ******************************************************************
 */

#include "keyboard.h"
#include "kernel.h"
#include "helper.h"
#include "io.h"
#include "ports.h"
#include "isr.h"
#include "util.h"

static char key_buffer[256]; // Save the keys pressed

char kbdus_table[128] = {
	0, 27, '1', '2', '3', '4', '5', '6', '7', '8', '9', '0',
	'-', '=', '\b', '\t', 'q', 'w', 'e', 'r', 't', 'y', 'u',
	'i', 'o', 'p', '[', ']', '\n', 0, 'a', 's', 'd', 'f',
	'g', 'h', 'j', 'k', 'l', ';', '\'', '`', 0, '\\', 'z',
	'x', 'c', 'v', 'b', 'n', 'm', ',', '.', '/', 0, '*', 0,
	' ', 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, '-',
	0, 0, 0, '+', 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
};

/* Handle keyboard input from user.
 */
static void keyboard_callback(registers_t *regs)
{
	char scancode = inb(0x60);

	if(scancode == '\b') {
		backspace(key_buffer);
		print_bkspc();
	} else if(scancode == '\n') { // Enter/Return
		user_input(key_buffer);
		key_buffer[0] = '\0';
	} else {
		char letter = kbdus_table[(int)scancode];
		char str[2] = {letter, '\0'};
		append(key_buffer, letter);
		print(str);
	}
	(void)regs;
}
/* Initialize the keyboard.
 */
void install_keyboard(void)
{
	register_interrupt_handler(IRQ1, keyboard_callback);
}

Posted: **Mon Jul 06, 2020 4:00 pm**

Code: Select all

static uint8_t multibyte = 0;

if( multibyte == 0xe0 )
{
	if( scancode >= 0x80 )
	{
		/* handle two-byte key release scan code */
	}
	else
	{
		/* handle two-byte key press scan code */
	}
	multibyte = 0;
}
else if( multibyte == 0xe1 )
{
	switch( scancode )
	{
		case 0x1d:
		case 0x45:
		case 0x9d:
		case 0xe1:
			/* you may want to verify you receive these in the right order */
			break;
		case 0xc5:
			/* handle pause key here */
			multibyte = 0;
			break;
		default:
			/* shouldn't happen */
			/* perhaps warn the user with an error */
			multibyte = 0;
			break;
	}
}
else
{
	if( scancode == 0xe0 || scancode == 0xe1 )
	{
		multibyte = scancode;
	}
	else if( scancode >= 0x80 )
	{
		/* handle one-byte key release scan code */
	}
	else
	{
		/* handle one-byte key press scan code */
		/* most of the code you've already written could go here */
	}
}

Something like this?

edit: forgot a couple very important lines of code

Posted: **Mon Jul 06, 2020 6:48 pm**

Thanks for the example, but one problem with my new code is it doesn't append to the buffer. Not sure why not though it should. Why isn't it appending?

Posted: **Mon Jul 06, 2020 7:15 pm**

Well, I forgot a couple very important lines in the example, so perhaps check it again.

I don't see any reason why it wouldn't be appending. Have you stepped through the function with a debugger to see if control flow is going in an odd direction?

Posted: **Mon Jul 06, 2020 8:33 pm**

Okay checked in the debugger and the user_input function shows char *input as empty. I'm not sure why there isn't anything wrong with my C code. Or at least I don't know, my C code should be passing key_buffer into input in the user_input(char *input) function shouldn't it? Unless there is something I don't know about at this low of level of code in C.

Posted: **Mon Jul 06, 2020 8:47 pm**

It sounds like key_buffer is actually empty, and what you should be looking at in the debugger are the calls to append() that are supposed to fill it.

Posted: **Mon Jul 06, 2020 9:49 pm**

Yes, the call to append is supposed to fill the key_buffer. The append and backspace functions are located in kernel/common/helper.c.

Posted: **Mon Jul 06, 2020 10:27 pm**

But did you step through it in the debugger to see if it actually does fill key_buffer?

Your strlen() and strcmp() functions don't look quite right...

Posted: **Tue Jul 07, 2020 3:01 am**

Yep that was it, glad you notice strlen and strcmp not looking right. I corrected them and it works perfect now. Thanks marking as solved.

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[Solved] Keyboard handler and translation table problem.

[Solved] Keyboard handler and translation table problem.

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