6502-OS/system/spi.s65

;********************************************************************************
; @module SPI
; @type driver
; @details
; @depends IO-W65C22N
;********************************************************************************

.include "system/system.s65"
.include "programs/print_slow.s65"

.ifndef INCLUDE_SPI
INCLUDE_SPI = 1
.scope spi_p


.zeropage
code_page:          .res 2  ; SPI_CODE_START + pages_written * 256
.bss
bytes_written:      .res 1
pages_written:      .res 1

.include "util/math.s65"
; spi-transferred code will be placed here
.segment "SPI"
SPI_CODE_START:
    lda '$'
    jsr lcd_char
    lda #<TEST_FMT
    sta ARG0
    lda #>TEST_FMT
    sta ARG1
    lda #<TEST_OUT
    sta ARG2
    lda #>TEST_OUT
    sta ARG3
    lda #$a9
    sta ARG4
    lda #$3c
    sta ARG5
    lda #$10
    sta ARG6
    jsr strf
    Print TEST_OUT
@spiloop:
    lda IO1 + IO::RA
    lda IO2 + IO::RA
    nop
    bra @spiloop
    jmp home

; TODO allocate zp memory
fmt_idx = $30
out_idx = $31
;********************************************************************************
; @function Format a string
; @details
;   If there is no value to be read, the Pz will be set
;   Formats:
;   - u: unsigned decimal integer (1 byte)
;   - U: unsigned decimal integer (2 bytes)
; @param ARG0-1: Format string address
; @param ARG2-3: Output string address
; @param ARG4+:  Additional parameters
; @returns 
; @modifies: A, Y
;********************************************************************************
.proc strf
    stz out_idx
    stz fmt_idx
    ldy #0  ; position in string
    ldx #0  ; index of format args
@loop:
    ldy fmt_idx
    lda (ARG0),y
    beq @null
    cmp #'%'
    beq @percent
@normal_char:  ; store A in output string
        ldy out_idx
        sta (ARG2),y
        inc fmt_idx
        inc out_idx
        beq @out_overflow
        bra @loop
@percent:  ; check for format in next position
        iny
        sty fmt_idx
        lda (ARG0),y
        beq @null
        ; formats
        cmp #'x'
        beq @format_hex1
        bra @normal_char
@format_hex1:   ; 1 byte hex -> 2 chars
            lda ARG4,x
            phx
            jsr int8_to_hex_str
            ldy out_idx
            sta (ARG2),y  ; most sig digit
            iny
            beq @out_overflow
            txa
            sta (ARG2),y  ; least sig digit
            iny
            beq @out_overflow
            sty out_idx
            plx
            inx  ; 1 byte of args handeled
            ; bra @format_return
@format_return:  ; increment fmt_idx to swallow the formating char
        inc fmt_idx
        bra @loop
@out_overflow:  ; store 0 in last position
    ldy #$ff
    sty out_idx
@store_null:
    lda #0
@null:  ; store and return
    ldy out_idx
    sta (ARG2),y
@rts:
    rts
.endproc


;********************************************************************************
; @function Convert a 1 byte number into two hex characters
; @param A: Number to convert
; @returns A: Most significant digit
; @returns X: Least significant digit
; @modifies X,Y,A
;********************************************************************************
.proc int8_to_hex_str
    pha
    and #%00001111
    tay
    ldx HEX_CHARS,y
    pla
    div A,16
    and #%00001111
    tay
    lda HEX_CHARS,y
    rts
.endproc
    
    


HEX_CHARS: .byte "0123456789ABCDEF"

TEST_FMT: .asciiz "%x -> %x -> %x:)"
TEST_OUT: .asciiz "TESTOUT"

; SPI_P = as peripheral
.code
.struct SPI_P_Pins
    ; VIA addresses
    DDR_a   .word   ; address of the data direction register
    R_a     .word   ; address of the register
    ; pin mask
    SCLK_p  .byte   ; Serial Clock
    POCI_p  .byte   ; Peripheral Out / Controller In
    PICO_p  .byte   ; Peripheral In / Controller Out
    CSB_p   .byte   ; Chip Select
    ; settings
    CPOL    .byte   ; Clock Polarity
    CPHA    .byte   ; Clock Phase
.endstruct

;********************************************************************************
; @function Begin listening for SPI transfers
; @details
;   - initialize variables
;   - configure shift register to shift in under external clock
;   - enable shift register interrupts 
;********************************************************************************
.proc begin
    stz pages_written
    stz bytes_written
    ; store address in zp
    lda #<SPI_CODE_START
    sta code_page
    lda #>SPI_CODE_START
    sta code_page + 1
    ; todo USE MASKS
    ; set Shift register to shift in under external clock on CB1
    lda #IO::ACR::SR_SIN_PHIE
    sta SPI_IO + IO::ACR

    ; enable SR interrupts
    lda #(IO::IRQ::IRQ | IO::IRQ::SR)
    sta SPI_IO + IO::IER

    ; load SR to reset
    lda SPI_IO + IO::SR
    rts
.endproc

;********************************************************************************
; @function Stop listening for SPI transfers
; @details
;  Disables shift register interrupts
;********************************************************************************
.proc end
    ; disable SR interrupts
    lda #IO::IRQ::SR
    sta SPI_IO + IO::IER
    rts
.endproc
    


;********************************************************************************
; @function Read a byte from SPI
; @details
;  Reads a byte from the shift register and stores it in the SPI code buffer
;********************************************************************************
.proc read
    ldx bytes_written
    lda SPI_IO + IO::SR
    sta SPI_CODE_START,x
    inc bytes_written
    beq @new_page
    rts
@new_page:
    inc pages_written
    inc code_page + 1
    rts
.endproc

    
;********************************************************************************
; @function Initialize the IO Adapter for SPI
; @param ARG0-1 Address of the SPI_Pins struct
;********************************************************************************
;********************************************************************************
; @function Read bytes
; @param X Number of bytes to send
; @param ARG0-1 Address of the SPI_Pins struct
; @param ARG2-3 Address of the first byte
;********************************************************************************
.proc recv_data
.endproc
;********************************************************************************
; @function Send bytes
; @param X Number of bytes to send
; @param ARG0-1 Address of the SPI_Pins struct
; @param ARG2-3 Address of the first byte
;********************************************************************************
.proc send_data
.endproc

.endscope

    

.endif