View source for Programming:Keyboard scanning

== Hardware scancode table ==
{|{{Prettytable|width: 700px; font-size: 2em;}}
|'''Bit:<br>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

<pre>
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), c
ld b, &F4
in a, (c)
ld bc, &F782
out (c), c
ld bc, &F600
out (c), c
</pre>

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.

<pre>
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
</pre>

[[Category:Programming]]