560 Notes on Keyboard DEMO Driver
This note demonstrate a simple KBD driver AND how to install interrupt handlers in MTX. The driver handles lower case key press only. Thus, no shift, control (esc) keys, etc. 1. In main.c, install KBD interrupt handler (at vector 9) //***************** main.c file ******************************* #include "kbd.c" int inkmode = 1; // start in Kmode, ++ when enter Kmode, -- when exit Kmode main() { vid_init(); // must initialize display driver first before any print init(); kfork(); set_vec(80, int80h); // install KBD interrupt handler, initilize kbd driver set_vec(9, kbinth); kbinit(); lock(); set_vector(8, tinth); timer_init(); while(1){ // process may BLOCK while waitng for key if (rqueue[1].queue) tswitch(); } } 2. KBD driver: Every (interrupt-driven) device driver consists of TWO parts: Lower half: interrupt handler, on interrupt, get scan code, translate into ASCII char and save it into an input buf[]; Upper half: Process calls getc(), trying to get a char from buf[]. Synchronization between the 2 halves: Process BLOCK/SLEEP if no char in buf[]. Interrupt handler puts char into buf[] and UNBLOCK/WAKEUP process /************************** KCW ************************* To demo a simple KBD driver: handle lower case ASCII key press only No shift, esc, etc. Intended extensions: handle shift keys. esc keys add function keys *********************************************************/ #define KEYBD 0x60 /* I/O port for keyboard data */ #define PORT_B 0x61 /* port_B of 8255 */ #define KBIT 0x80 /* bit used to ack characters to keyboard */ #define KBSIZE 64 // size of input buffer in bytes #define N_SCAN 105 /* Number of scan codes */ /* Scan codes to ASCII for unshifted keys; unused keys are left out */ char unshift[N_SCAN] = { 0,033,'1','2','3','4','5','6', '7','8','9','0','-','=','\b','\t', 'q','w','e','r','t','y','u','i', 'o','p','[',']', '\r', 0,'a','s', 'd','f','g','h','j','k','l',';', 0, 0, 0, 0,'z','x','c','v', 'b','n','m',',','.','/', 0,'*', 0, ' ' }; /* Scan codes to ASCII for shifted keys; unused keys are left out */ char shift[N_SCAN] = { 0,033,'!','@','#','$','%','^', '&','*','(',')','_','+','\b','\t', 'Q','W','E','R','T','Y','U','I', 'O','P','{','}', '\r', 0,'A','S', 'D','F','G','H','J','K','L',':', 0,'~', 0,'|','Z','X','C','V', 'B','N','M','<','>','?',0,'*', 0, ' ' }; int kbdata; // has KBD input flag char kbc; // data char int kbinit() { printf("kbinit() : "); kbdata = 0; // flag = 0 initially enable_irq(1); out_byte(0x20, 0x20); printf("kbinit done\n\r"); } /************************************************************************ kbhandler() is the kbd interrupt handler. PC's kbd generates 2 interrupts for each key typed; one when the key is pressed and another one when the key is released. Each key generates a scan code. The scan code of a key release is 0x80 + the scan code of key pressed. When the kbd interrupts, the scan code is in the data port (0x60) of the KBD interface. First, read the scan code from the data port. Then ack the key input by strobing its PORT_B at 0x61. Some special keys generate ESC key sequences,e.g. arrow keys. Then process the scan code: 1. Ignore key releases, thus no special keys, such as shift. For normal keys: translate into LOWER CASE ASCII char. 2. Raise the kbdata flag to allow a busy waiting process to get the key ************************* Lower half driver ******************************/ int kbhandler() { int scode, value, c; /* Fetch the character from the keyboard hardware and acknowledge it. */ scode = in_byte(KEYBD);/* get the scan code of the key struck */ value = in_byte(PORT_B);/* strobe the keyboard to ack the char */ out_byte(PORT_B, value | KBIT);/* first, strobe the bit high */ out_byte(PORT_B, value); /* then strobe it low */ printf("kb interrupt %x\n", scode); // should see the scand code if (scode & 0x80) // ignore key release goto out; kbc = unshift[scode]; // translate scan code into ASCII char kbdata = 1; // raise kbdata flag out: out_byte(0x20, 0x20); } /**************************** upper half driver ***********************/ // process call getc() to return a char from KBD, by busy waiting loop int getc() { char c; unlock(); // syscall to MTX kernel MAY have masked out interrupts while(kbdata==0); // busy waiting loop for kbdata = 1 c = kbc & 0x7F; // in general, get char from a buffer area kbbuf[] lock(); kbdata = 0; // this is a CR between process and interrupt unlock(); return c; } ASSIGNMENT: Re-design the simple kbd driver: (1). Use input buffer kbbuf[KBSIZE] to store input keys. (2). Use sleep/wakeup OR P/V on semaphores to synchronize process and interrupt handler. (3). Implement it on our MTX system. Self-challenge: Modify the simple kbd driver to allow UPPER case keys. COMMENTS on How TO Install Interrupt Handlers in MTX: ! ***************** ts.s file for interrupt handlers ********************* .globl _procsize .globl _inkmode ! global from t.c; .globl _int80h, _kcinth .globl _tinth, _thandler .globl _kbinth, _kbhandler USS = 4 USP = 6 ! as86 macro: parameters are ?1 ?2, etc ! as86 -m -l listing src (listing with macro expansion) MACRO INTH push ax push bx push cx push dx push bp push si push di push es push ds push cs pop ds inc _inkmode ! enter Kmode : ++inkmode cmp _inkmode,#1 ! if inkmode == 1 ==> interrupt was in Umode jg ?1 ! was in Kmode: bypass saving uss,usp ! was in Umode: save interrupted (SS,SP) into proc mov si,_running ! ready to access proc mov USS[si],ss ! save SS in proc.USS mov USP[si],sp ! save SP in proc.USP ! change DS,ES,SS to Kernel segment mov di,ds ! stupid !! mov es,di ! CS=DS=SS=ES in Kmode mov ss,di mov sp, _running ! sp -> running's kstack[] high end add sp, _procsize ?1: call _?1 ! call handler in C br _ireturn ! return to interrupted point MEND ! instrrupt handler entry points _int80h: INTH kcinth _tinth: INTH thandler _kbinth: INTH kbhandler !other interrupt handlers !*===========================================================================* !* _ireturn and goUmode() * !*===========================================================================* ! ustack contains flag,ucs,upc, ax,bx,cx,dx,bp,si,di,es,ds ! uSS and uSP are in proc _goUmode: _ireturn: cli dec _inkmode ! --inkmode cmp _inkmode,#0 ! inkmode==0 means was in Umode jg xkmode ! restore uSS, uSP from running PROC mov si,_running ! si -> proc mov ax,USS[si] mov ss,ax ! restore SS mov sp,USP[si] ! restore SP xkmode: pop ds pop es pop di pop si pop bp pop dx pop cx pop bx pop ax iret /************************* KBD scan code info ***************************** US 104-key keyboard, set 1 scancodes "Make" code is generated when key is pressed. "Break" code is generated when key is released. Hex value of make code for each key is shown. Most keys: one-byte make code = nn one-byte repeat code = nn one-byte break code = 80h + nn "Gray" keys (not on original 84-key keyboard): two-byte make code = E0nn two-byte repeat code = E0nn two-byte break code = E0 followed by 80h + nn "Gray" keys noted by [1] are NumLock-sensitive. When the keyboard's internal NumLock is active: four-byte make code = E02AE0nn two-byte repeat code = E0nn four-byte break code = E0 followed by 80h + nn followed by E0AA ____ ___________________ ___________________ ___________________ | | | | | | | | | | | | | | | | | |Esc | |F1 |F2 |F3 |F4 | |F5 |F6 |F7 |F8 | |F9 |F10 |F11 |F12 | | | | | | | | | | | | | | | | | | | 01| | 3B| 3C| 3D| 3E| | 3F| 40| 41| 42| | 43| 44| 57| 58| |____| |____|____|____|____| |____|____|____|____| |____|____|____|____| __________________________________________________________________________ | | | | | | | | | | | | | | | | |~ |! |@ |# |$ |% |^ |& |* |( |) |_ |+ || |bksp| |` |1 |2 |3 |4 |5 |6 |7 |8 |9 |0 |- |= |\ | | | 29| 02| 03| 04| 05| 06| 07| 08| 09| 0A| 0B| 0C| 0D| 2B| 0E| |____|____|____|____|____|____|____|____|____|____|____|____|____|____|____| | | | | | | | | | | | | | | | |Tab |Q |W |E |R |T |Y |U |I |O |P |{ |} | | | | | | | | | | | | | |[ |] | | | 0F| 10| 11| 12| 13| 14| 15| 16| 17| 18| 19| 1A| 1B| | |____|____|____|____|____|____|____|____|____|____|____|____|____| | | | | | | | | | | | | | | | |Caps|A |S |D |F |G |H |J |K |L |: |" | Enter | | | | | | | | | | | |; |' | | | 3A| 1E| 1F| 20| 21| 22| 23| 24| 25| 26| 27| 28| 1C| |____|____|____|____|____|____|____|____|____|____|____|____|______________| | | | | | | | | | | | | | | L Shift |Z |X |C |V |B |N |M |< |> |? | R Shift | | | | | | | | | |, |. |/ | | | 2A| 2C| 2D| 2E| 2F| 30| 31| 32| 33| 34| 35| 36| |_________|____|____|____|____|____|____|____|____|____|____|______________| | | | | | | | | | |L Ctrl | L win | L Alt | space | R Alt | R win | menu |R Ctrl | | |[1] | | | |[1] |[1] | | | 1D| E05B| 38| 39| E038| E05C| E05D| E01D| |_______|_______|_______|__________________|_______|_______|_______|_______| [2] For PrintScreen/SysRq key: make code = E02AE037, repeat code = E037, break code = E0B7E0AA [3] The Pause/Break key does not repeat, and it does not generate a break code. Its make code is E11D45E19DC5 ____ ____ ____ | | | | |Prt |Scrl|Paus| |Scrn|Lock|Brk | | [2]| 46| [3]| |____|____|____| ____ ____ ____ ____ ____ ____ ____ | | | | | | | | | |Ins |Home|PgUp| |Num |/ |* |- | |[1] |[1] |[1] | |Lock| | | | |E052|E047|E049| | 45|E035| 37| 4A| |____|____|____| |____|____|____|____| | | | | | | | | | |Del |End |PgDn| |7 |8 |9 | | |[1] |[1] |[1] | |Home|(U) |PgUp| | |E053|E04F|E051| | 47| 48| 49| | |____|____|____| |____|____|____| | | | | |+ | |4 |5 |6 | | |(L) | |(R) | | | 4B| 4C| 4D| 4E| ____ |____|____|____|____| | | | | | | | |(U) | |1 |2 |3 | | |[1] | |End |(D) |PgDn| | |E048| | 4F| 50| 51|Ent | ____|____|____ |____|____|____| | | | | | | | | | |(L) |(D) |(R) | |0 |. | | |[1] |[1] |[1] | |Ins |Del | | |E04B|E050|E04D| | 52| 53|E01C| |____|____|____| |_________|____|____| code key code key code key code key ---- --- ---- --- ---- --- ---- --- 01 Esc 0F Tab 1D L Ctrl 2B \| 02 1! 10 Q 1E A 2C Z 03 2" 11 W 1F S 2D X 04 3# 12 E 20 D 2E C 05 4$ 13 R 21 F 2F V 06 5% 14 T 22 G 30 B 07 6^ 15 Y 23 H 31 N 08 7& 16 U 24 J 32 M 09 8* 17 I 25 K 33 ,< 0A 9( 18 O 26 L 34 .> 0B 0) 19 P 27 ;: 35 /? 0C -_ 1A [{ 28 '" 36 R Shift 0D =+ 1B ]} 29 `~ 37 * 0E BackSpace 1C Enter 2A L Shift 38 L Alt code key code key code key code key ---- --- ---- --- ---- --- ---- --- 39 Space 41 F7 49 PageUp 9 51 PageDown 3 3A CapsLock 42 F8 4A - 52 Insert 0 3B F1 43 F9 4B (left) 4 53 Del . 3C F2 44 F10 4C 5 3D F3 45 NumLock 4D (right) 6 57 F11 3E F4 46 ScrollLock 4E + 58 F12 3F F5 47 Home 7 4F End 1 40 F6 48 (up) 8 50 (down) 2 code key ---- --- E01C Enter (on numeric keypad) E01D R Ctrl E02A make code prefix for keyboard internal numlock E02AE037 PrintScreen make code E035 / E037 PrintScreen repeat code E038 R Alt E047 Home E048 (up) E049 PageUp E04B (left) E04D (right) E04F End E050 (down) E051 PageDown E052 Insert E053 Del E05B L Win E05C R Win E05D Menu E0AA break code suffix for keyboard internal numlock E0B7E0AA PrintScreen break code E11D45E19DC5 Pause *****************************************************************************/