ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ³ Programming the Keyboard ³ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ Written for the PC-GPE by Mark Feldman e-mail address : u914097@student.canberra.edu.au myndale@cairo.anu.edu.au ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ³ THIS FILE MAY NOT BE DISTRIBUTED ³ ³ SEPARATE TO THE ENTIRE PC-GPE COLLECTION. ³ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ ÚÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ ³ Disclaimer ³ ÀÄÄÄÄÄÄÄÄÄÄÄÄÙ I assume no responsibility whatsoever for any effect that this file, the information contained therein or the use thereof has on you, your sanity, computer, spouse, children, pets or anything else related to you or your existance. No warranty is provided nor implied with this information. ÚÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ ³ Overview ³ ÀÄÄÄÄÄÄÄÄÄÄÙ The operation of the keyboard is really quite simple. Every time a key is pressed or released an interrupt 9 is generated, and reading the value from port 60h tells you what happened. ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ ³ Decoding the Keyboard Byte ³ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ So let's say you've installed an interrupt handler to handle all keyboard events and when an interrupt is generated your handler reads the byte from port 60h. What now? Well..each key on the keyboard has an associated scan code which is contained in the lower 7 bits of the byte. The most significant bit (ie bit 7) tells you what was actually done, 0 = key was just pressed, 1 = key was just released. If someone had just pressed the ESC key for instance, the port will show a value of 1 (1 is the ESC key's scan code). If they hold their finger on the button the keyboard will keep generating interrupt 9's and each time the port will still show a value of 1. When the person releases the key a final interrupt will be generated and the port will return 129 (1 + 128, since the high bit will be set indicating the person has released the key). Well...it's almost this simple. Some keys are "extended" keys. When an extended key is pressed an interrupt is generated and the keyboard port will return a value of 224 (E0h). This means that an extended key was pressed and it's *extended* scan code will be available during the *next* interrupt. Note that the left control key has a scan code of 29, while the *right* control key has an *extended* scan code of 29. The same applies to the alt keys and the arrow keys (keypad arrows vs the other ones). It would be nice if all keys were created equal and we could just throw away the 224 extended bytes and handle all the other bytes normally. Unfortunately there are two buttons which on my machine at least (and others I have tested) do some really weird stuff: PrtScn ÄÄÄÄÄÄ Pressing this button will send *2* extended characters to the handler, 42 and 55, so the actual byte sequence will be 224, 42, 224, 55. (Also note that the left shift key has a regular scan code of 42, so there goes our idea of just throwing 224's away). Only the extended 55's are sent during auto-repeat. When the key is released, the two are sent again with the high bits set (224, 170, 224, and 183). If any of the shift or control keys are being held down when the PrtScn button is pressed then only the (224, 55) is sent when the key is pressed and only the (224, 183) is sent when it's released. If the alt key is being held down (System Request) then the key behaves like an ordinary key with scan code 84. The practical upshot of all this is that the handlers you write to handle normal keys and extended keys will work fine with all the different PrtScn combinations (although a program would have to check normal key 84 *AND* extended key 55 in order to determine if the key is currently being pressed). Pause/Break ÄÄÄÄÄÄÄÄÄÄÄ Welcome to hell. If you press this key while either of the the control keys are being held down, it will behave like extended key 70, at all other times it will send the following bytes: (225, 29, 69, 225, 157, 197). Holding the key down does not result in autorepeat. Taking your finger off the key does not send any extra bytes, they appear to be sent after the "key down" bytes when you first press the key. Notice that 225 isn't 224, so our normal extended character handler will not take care of this. My personal theory is that while a scan code of 224 (E0h) means there is 1 more character following, a scan code of 225 (E1h) means there are *2* more following. I've seen a number of keyboard handler libraries and they all seem to overlook this key. So why not be the first kid on your block to have a keyboard handler which properly supports the Pause/Break key? CHECK IT OUT!! ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ ³ Writing a Handler ³ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ Writing a keyboard handler is fairly straightforward. This section will show how to do it in Pascal (you C and asm programmers would probably already know this stuff anyway). First we'll declare a few things we'll need: const KEYBOARDINTR = 9; KEYBOARDPORT = $60; var BIOSKeyboardHandler : procedure; CallBIOSHandler : boolean; The CallBIOSHandler variable will be initialised by the calling program. If we also want the BIOS handler to process all keystrokes then this variable must be set to true. Next we need to store the value of the current handler and set up own our own one. We'll use a procedure called KeyboardHandler to handle the actual interrupt. CallBIOSHandler := false; { ...or set it to true if you want. } GetIntVec(KEYBOARDINTR, @BIOSKeyboardHandler); SetIntVec(KEYBOARDINTR, Addr(KeyboardHandler)); Ok, so everything is now set up and our handler will now be able to process all keyboard events. The actual interrupt handler could look like this: {$F+} procedure KeyboardHandler(Flags, CS, IP, AX, BX, CX, DX, SI, DI, DS, ES, BP: Word); interrupt; var key : byte; begin key := Port[KEYBOARDPORT]; { PROCESS THE KEYSTROKE HERE } if CallBIOSHandler then { Call the BIOS keyboard handler if the calling program wants us to } begin asm pushf end; BIOSKeyboardHandler; end { Otherwise just acknowledge the interrupt } else Port[$20] := $20; end; {$F-} When the program is finished we can set the old keyboard handler again: SetIntVec(KEYBOARDINTR, @BIOSKeyboardHandler); ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ ³ A Word of Warning ³ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ When I was writing a simple handler to test the info in this file I did something REALLY stoopid which I would like to share with the world. I thought that my program was stuffing the keyboard up because when I exited the program my editor (Borland Pascal 7.0) would act as though the control button was being held down (I'm sure some of you have already started laughing by now). I had to press it after each time I ran the program just to sort it out. After spending a few hours looking all over the place for info on what could possibly be wrong I realised what I was doing. I was pressing CTRL-F9 to compile the program which would also immediately make it run and I was releasing the control key when my program was running, ie the regular BIOS handler was not getting the control key's "key up" command and still thought it was being held down when my program returned control to it. Moron..... ÚÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ ³ Scan Codes ³ ÀÄÄÄÄÄÄÄÄÄÄÄÄÙ The following is a list of all the regular key scan codes in numerical order: Scan Scan Code Key Code Key ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ 1 ESC 44 Z 2 1 45 X 3 2 46 C 4 3 47 V 5 4 48 B 6 5 49 N 7 6 50 M 8 7 51 , < 9 8 52 . > 10 9 53 / ? 11 0 54 RIGHT SHIFT 12 - _ 55 * (KEYPAD) 13 = + 56 LEFT ALT 14 BACKSPACE 57 SPACEBAR 15 TAB 58 CAPSLOCK 16 Q 59 F1 17 W 60 F2 18 E 61 F3 19 R 62 F4 20 T 63 F5 21 Y 64 F6 22 U 65 F7 23 I 66 F8 24 O 67 F9 25 P 68 F10 26 [ { 69 NUMLOCK (KEYPAD) 27 ] } 70 SCROLL LOCK 28 ENTER (RETURN) 71 7 HOME (KEYPAD) 29 LEFT CONTROL 72 8 UP (KEYPAD) 30 A 73 9 PGUP (KEYPAD) 31 S 74 - (KEYPAD) 32 D 75 4 LEFT (KEYPAD) 33 F 76 5 (KEYPAD) 34 G 77 6 RIGHT (KEYPAD) 35 H 78 + (KEYPAD) 36 J 79 1 END (KEYPAD) 37 K 80 2 DOWN (KEYPAD) 38 L 81 3 PGDN (KEYPAD) 39 ; : 82 0 INSERT (KEYPAD) 40 ' " 83 . DEL (KEYPAD) 41 ` ~ 87 F11 42 LEFT SHIFT 88 F12 The following is a list of all the extended key scan codes in numerical order: Scan Scan Code Key Code Key ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ 28 ENTER (KEYPAD) 75 LEFT (NOT KEYPAD) 29 RIGHT CONTROL 77 RIGHT (NOT KEYPAD) 42 PRINT SCREEN (SEE TEXT) 79 END (NOT KEYPAD) 53 / (KEYPAD) 80 DOWN (NOT KEYPAD) 55 PRINT SCREEN (SEE TEXT) 81 PAGE DOWN (NOT KEYPAD) 56 RIGHT ALT 82 INSERT (NOT KEYPAD) 71 HOME (NOT KEYPAD) 83 DELETE (NOT KEYPAD) 72 UP (NOT KEYPAD) 111 MACRO 73 PAGE UP (NOT KEYPAD)