6502-OS/spicode.s65

.include "system.h65"
.include "string.h65"
.include "lcd.h65"
.include "math.h65"
.include "keypad.h65"
.include "chars.h65"
.import homeloop:absolute
.import home:absolute

.segment "SPI"
.export CODE_START

.import memcopy

.scope kb
KB_IO = IO1
.endscope


CODE_START:
.assert * = $5000, error, "SPI Code not at $5000"
    jsr lcd::clear
    lda #'$'
    jsr lcd::print_char

    ; stz kp::_DEBUG_VAL
; @loop:
    ; lda kp::_DEBUG_VAL
    ; beq @loop
    ; stz kp::_DEBUG_VAL
    ; cmp #'*'
    ; jeq homeloop
    ; jsr lcd::print_char
    ; bra @loop

    lda #<kb_irq1
    sta ARG0
    lda #>kb_irq1
    sta ARG1
    lda #<$3000
    sta ARG2
    lda #>$3000
    sta ARG3
    ldy #20
    jsr memcopy

    lda #<kb_irq2
    sta ARG0
    lda #>kb_irq2
    sta ARG1
    lda #<$3100
    sta ARG2
    lda #>$3100
    sta ARG3
    ldy #20
    jsr memcopy

    lda #'?'
    jsr lcd::print_char

    ; PrintNC $3000

    jsr kbinit

    lda #'%'
    jsr lcd::print_char

    stz kp::_DEBUG_VAL
    ldy #0

@loop:
    lda kp::_DEBUG_VAL
    beq @loop
    stz kp::_DEBUG_VAL
    cmp #'*'
    jeq homeloop
    cmp #'1'
    beq @l1
    cmp #'2'
    beq @l2
    cmp #'3'
    beq @l3
    cmp #'A'
    beq @lA
    cmp #'B'
    beq @lB
    cmp #'C'
    beq @lC
    jsr lcd::print_char
    bra @loop
@l1:
    ; jsr irq_on_shift_reg
    jsr $3000
    lda #'*'
    jsr lcd::print_char
    bra @loop
@l2:
    ; jsr irq_on_timer
    jsr $3100
    lda #'#'
    jsr lcd::print_char
    bra @loop
@l3:
    lda $3000,y
    jsr lcd::print_char
    iny
    bra @loop
@lA:
    lda kb::KB_IO + IO::SR
    jsr lcd::print_char
    bra @loop
@lB:
    Strf fmt_str, out_str, keycode
    Print out_str
    bra @loop
@lC:
    jsr lcd::clear
    bra @loop


kbinit:
    lda #'['
    jsr lcd::print_char
    ; - use the shift register interrupts to read the first 8 bits
    ;   set shift register to shift in under external clock on CB1
    ; - configure timer for timing the read of the last 3 bits
    ;   timer 2 one shot mode is sufficient, leaves T1 available
    lda #(IO::ACR::SR_SIN_PHIE | IO::ACR::T2_IRQ_LOAD)
    tsb kb::KB_IO + IO::ACR
    ; the 3 last bits take about 230us, at @1MHz => wait 230 cycles and then the shift register
    lda #230
    sta kb::KB_IO + IO::T2CL
    stz key_read
    stz key_read+1

    ; enable SR interrupts
    lda #(IO::IRQ::IRQ | IO::IRQ::SR)
    sta kb::KB_IO + IO::IER
    ; load SR to reset
    lda kb::KB_IO + IO::SR
    lda #']'
    jsr lcd::print_char
    rts


;; @details
;;  IO::SR has to be read before the next bit is shifted in, which happens ~75us after the irq
;;  at 1MHz, handlings this interrupt takes about 50us (without any additional debug code), so it should work
irq_on_shift_reg:
    ; lda #'{'
    ; jsr lcd::print_char
    lda kb::KB_IO + IO::SR
    sta key_read
    stz kb::KB_IO + IO::SR

    ; disable SR interrupts
    lda #IO::IRQ::SR
    sta kb::KB_IO + IO::IER
    ; enable timer interrupts
    lda #(IO::IRQ::IRQ | IO::IRQ::T2)
    sta kb::KB_IO + IO::IER
    ; start timer
    lda #1
    sta kb::KB_IO + IO::T2CH
    ; lda #'}'
    ; jsr lcd::print_char
    rts
    

irq_on_timer:
    ; lda #'<'
    ; jsr lcd::print_char
    lda kb::KB_IO + IO::SR
    sta key_read + 1

    lda kb::KB_IO + IO::T2CL  ; clear interrupt flag

    ; disable timer interrupts
    lda #(IO::IRQ::T2)
    sta kb::KB_IO + IO::IER
    ; enable shift register interrupts
    lda #(IO::IRQ::IRQ | IO::IRQ::SR)
    sta kb::KB_IO + IO::IER
    ; reset SR
    stz kb::KB_IO + IO::SR

    ; lda #'|'
    ; rotate bit 2 (last bit of keycode) into the carry
    ror
    ror
    ror
    lda key_read  ; not affecting carry
    rol  ; rotate carry into byte, rotate startbit into carry
    ; TODO byte is inverted, maybe consider wasting 256 bytes for a bit reverse lookup table?
    sta keycode

    Strf fmt_str2, out_str, keycode, key_read, key_read+1
    PrintNC out_str

    stz key_read
    stz key_read+1

    rts

key_read: .res 2
keycode:  .res 1
kb_irq1:
    ; lda #'!'
    ; jsr lcd::print_char
    jsr irq_on_shift_reg
    ; lda #':'
    ; jsr lcd::print_char
    rts
.byte '='
kb_irq2:
    ; lda #'?'
    ; jsr lcd::print_char
    jsr irq_on_timer
    ; lda #';'
    ; jsr lcd::print_char
    rts
.byte '@'

out_str: .res 40
fmt_str: .asciiz "kc%x;"
fmt_str2: .asciiz "kc%x-%x-%x;     "