;********************************************************************************
; @module keypad4x4
; @type driver
; @device 4x4 Matrix Keypad
; @details
;   The LCD must be connected to a W65C22N Interface Chip:
;     - IO.RA0-7  -> 
; @requires KP_IO: Base Address of IO Chip
; @depends IO-W65C22N 
;********************************************************************************


.ifndef INCLUDE_KEYPAD
INCLUDE_KEYPAD = 1
.ifndef KP_IO
    .fatal "KP_IO is not defined: set it to the base address of the IO chip of the Keypad"
.endif

.zeropage
_KP_COLUMN:         .res 1  ; for storing stuff
_KP_DEBUG_VAL:      .res 1  ; for storing the last char DEBUG

.bss  ; reserve space or ringbuffer
KP_BUF_SIZE = 10
RBUF_MEM_START: .res KP_BUF_SIZE
RBUF_MEM_END = RBUF_MEM_START + KP_BUF_SIZE - 1   
.define RBUF_NAME "keypad"
.include "buffer.s65"

.code
.proc kp_init
    ; todo remove later and test
    lda #$ff
    sta KP_IO+IO::DDRA
    stz KP_IO+IO::RA

    ; INIT KEYPAD 
    ; todo: use masks
    lda #%11110000; KP_IO+IO::RA 0-3 output
    sta KP_IO+IO::DDRA
    ; output 0, key press will pull input pin low
    stz KP_IO+IO::RA        
    stz KP_IO+IO::ACR

    ; lda #%00010000  ; set CA1 to interrupt on pos. edge
    ; todo: use masks
    lda #IO::PCR::CA1_IP_AE
    sta KP_IO+IO::PCR
    jsr rb_keypad_init  ; init keybuffer
    lda #(IO::IRQ::IRQ | IO::IRQ::CA1)  ; enable interrupt for CA1 on KP_IO
    sta KP_IO+IO::IER
    rts
.endproc

;********************************************************************************
; @function Read which key is pressed on the keypad
; @details
;   Checks which key is pressed and stores it in the keybuffer
;   The value stored in the keybuffer is the offset which must be added to 
;   kp_VALUES to retrieve the key that was pressed
;********************************************************************************
.proc kp_read_on_irq
    ; test each "row" and check which column is 1
    ; TODO dont check every column if the value has been found
    lda #%11100000
    ldx #$00
    jsr @kp_read_column
    lda #%11010000
    ldx #$04
    jsr @kp_read_column
    lda #%10110000
    ldx #$08
    jsr @kp_read_column
    lda #%01110000
    ldx #$0c
    jsr @kp_read_column
    stz KP_IO+IO::RA
    lda KP_IO+IO::RA  ; clear interrupt flag again beceause it might be set again through the above tests
    rts
@kp_read_column:
    sta KP_IO+IO::RA
    lda KP_IO+IO::RA
    sta _KP_COLUMN  ; store result in zeropage so that bbr can be used
    bbr0 _KP_COLUMN,@kp_write  ; row 1
    inx
    bbr1 _KP_COLUMN,@kp_write  ; row 3
    inx
    bbr2 _KP_COLUMN,@kp_write  ; row 2
    inx
    bbr3 _KP_COLUMN,@kp_write  ; row 4
    rts
@kp_write:
    lda _KP_VALUES,x
    ; TODO use ringbuffer
    sta _KP_DEBUG_VAL
    jsr rb_keypad_write
    rts
.endproc

.rodata
_KP_VALUES:
    .byte "174*"
    .byte "2850"
    .byte "396#"
    .byte "ACBD"
    ; keypad conencted so that 
    ; row 1 = PA0
    ; row 2 = PA2
    ; row 3 = PA1
    ; row 4 = PA3
.endif