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I have writen a basic keyboard driver to get the key pressed and then outputit to the screen, but ive had a probolem when trying to add the shift keys, when ever i
press a key it now prints out the character from both keymaps, so if any of you get a chance to have a look at it for me i would be very greatful:
Press a key it now prints out the character from both keymaps
Could it be that your code prints the make-code and break-code for each key ? Also make sure that 'shift_code' is either a global variable or a static local in your actual code.
Thanks, it now works fine when i press shift but still prints from both keymaps if shift is now pressed, you were right it is printing the breakcodes aswell, so how would i stop it fom printing the breakcodes?
I'm not certain I quite understand your code - why are you ORing with 0x80 at the start? You're looking for an AND I think - ORing will mean that it will always set shift as being down. Here's some heavily commented sample code (may well not compile - I've just typed it OTOH).
unsigned char scancode;
unsigned shift_state = 0;
char asciicode;
scancode = inportb(0x60); // Read from keyboard controller
if(scancode & 0x80)
{
// If bit 15 is set, then this is a key break code
switch(scancode)
{
case 0xAA:
// 0xAA == 0x2A | 0x80 - the shift key break code
shift_state = 0;
break;
/* Note that the switch statement is overkill for just the shift key, but
* there may well be other keys for which you wish to do similar
* things (ctrl, alt, perhaps others peculiar to your OS). */
}
}
else
{
// If bit 15 isn't set, then it's a key make code
switch(scancode)
{
case 0x2A:
/* 0x2A is the shift key's scancode - we want to handle it specially
* as it isn't a printable character. */
shift_state = 1;
break;
default:
/* Where we handle the non-special cases - usually all the
* printable characters. */
/* I prefer, through laziness, to do it this way - I doubt there's
* much of a performance difference either way. */
asciicode = kbdus[scancode];
if(shift_state)
asciicode = kbdus_upper[scancode];
putch(asciicode); /* We'd want to replace this later, to place the
* key into a buffer of some sort, then read from
* it; or (later still, perhaps) send the key in a
* message to the active process. */
break;
}
}
outportb(0x20, 0x20); // Acknowldge IRQ
I'm not certain I quite understand your code - why are you ORing with 0x80 at the start?
From what I understand the line you're refering to compares the read-in scancode with the shift break-codes. The bitwise OR is only used to set the break-code bit for the comparison.
The code should actually work if you just add a last comparison before the table look-up:
Nevertheless I would recommend using a switch as Midas proposed. It will become much easier to read once you've added support for a few more modifier keys to your driver.
I got it working now, i just added a check to see if it was a make code or not as gaf said, but i am going to add in switch functions later, i just wanted to get the basics done first. i will use what Midas has done to help with the more complex parts, and setting up all of the other keys.
Thanks for all your help everyone.
I'm not certain I quite understand your code - why are you ORing with 0x80 at the start?
From what I understand the line you're refering to compares the read-in scancode with the shift break-codes. The bitwise OR is only used to set the break-code bit for the comparison.
Ah, right you are. Read it twice and managed to miss that. Thanks.
Thanks.