Last modified on 6 September 2006, at 10:42

Programming:Keyboard scanning

Revision as of 10:42, 6 September 2006 by 83.156.200.243 (Talk) (One line scanning routine)

Hardware scancode table

Bit:
Line
7 6 5 4 3 2 1 0
&40 F Dot ENTER F3 F6 F9 CURDOWN CURRIGHT CURUP
&41 F0 F2 F1 F5 F8 F7 COPY CURLEFT
&42 CONTROL \ SHIFT F4 ] RETURN [ CLR
&43 . /  :  ; P @ - ^
&44 , M K L I O 9 0
&45 SPACE N J H Y U 7 8
&46 V B F G T R 5 6
&47 X C D S W E 3 4
&48 Z CAPSLOCK A TAB Q ESC 2 1
&49 DEL - - - - - - -

One line scanning routine

This is a routine which scans one line of the keyboard directly. It is approximately 8% faster then the firmware routine and doesn't enable interrupts.

Input: A = line (&40 - &49)

Output: A = hardware keyboard value

Destroyed: BC

ld a, line	;use the value from the table above
ld bc, &F6C0
out (c), c
ld bc, &F40E
out (c), c
ld bc, &F792
out (c), c
ld b, &F6
out (c), a
ld b, &F4
in a, (c)
ld bc, &F782
out (c), c
ld bc, &F600
out (c), c

Now check for the value from the table e.g. with 'bit x,A' and a condition e.g. 'jp z,xxxx' or 'call z,xxxx'

Please note:

  • Bit = 0: Key is pressed
  • Bit = 1: Key is not pressed

Complete keyboard scanning routine

This routine scans the complete keyboard and writes all key status bits in a map.

keymap  ds 10  ;map with 10*8 = 80 key status bits (bit=0 key is pressed)

keyscan di              ;1 ##%%## C P C   VERSION ##%%##
        ld hl,keymap    ;3
        ld bc,#f782     ;3
        out (c),c       ;4
        ld bc,#f40e     ;3
        ld e,b          ;1
        out (c),c       ;4
        ld bc,#f6c0     ;3
        ld d,b          ;1
        out (c),c       ;4
        ld c,0          ;2
        out (c),c       ;4
        ld bc,#f792     ;3
        out (c),c       ;4
        ld a,#40        ;2
        ld c,#4a        ;2 44
loop    ld b,d          ;1
        out (c),a       ;4 select line
        ld b,e          ;1
        ini             ;5 read bits and write into KEYMAP
        inc a           ;1
        cp c            ;1
        jr c,loop       ;2/3 9*16+1*15=159
        ld bc,#f782     ;3
        out (c),c       ;4
        ei              ;1 8 =211 microseconds
        ret