DHT_REQUEST_L = $00
DHT_REQUEST_H = %01010000  ; = 20480 PHI2 pulses = 20,5 ms at 1 MHz

DHT_RECV_H = %10011100
DHT_RECV_L = %01000000  ; = 40000 PHI2 = 40ms

; Status Variables, Used to determine what is sent by temp module
DHT_STATUS = $400
DHT_NONE = 0
DHT_WAIT_REQ = 1
DHT_WAIT_RESP = 2
DHT_RECV = 3
DHT_DONE = 4

DHT_BIT = $401
DHT_BIT_ROT = $402


DHT_VALUES = $405  ; 
DHT_OFFSET = $403
DHT_OFF_RH_HIGH = 0  ; offsets to DHT_VALUES
DHT_OFF_RH_LOW = 1
DHT_OFF_T_HIGH = 2
DHT_OFF_T_LOW = 3
DHT_OFF_CHECKSUM = 4
DHT_OFF_DONE = 5


message_dht:  .asciiz "DHT-Request gesendet."
dht_wait:
    ldx #$00
dht_wait_:
    lda message_dht,x
    sta TO_PRINT,x
    inx
    bne dht_wait_
    jsr lcd_print_clear
dht_wait_loop:  ; check after every interrpt if dht program is done and then return home
    lda #'.'
    jsr _lcd_char
    wai
    lda DHT_STATUS
    cmp #DHT_DONE
    bne dht_wait_loop

dht_exit:
    jsr kb_read
    cmp #'*'
    jeq home
    bra dht_exit
    jmp return_home

dht_request:  ; send request to sensor
    sei
    
    lda #%00000001 ; set PA1-0 to output 0
    ora DDRA1
    sta DDRA1
    lda #(LCD_CLEAR | $00)
    sta PA1
    
    ; start timer
    lda #DHT_REQUEST_L
    sta T1L1
    lda #DHT_REQUEST_H
    sta T1H1

    lda #DHT_WAIT_REQ
    sta DHT_STATUS

    cli
    jmp dht_wait


dht_request_end:
    lda #%10000010
    sta IER2  ; enable Interrupt for CA1
    lda #%11111110
    and DDRA1
    sta DDRA1  ; set PA1-0 to input

    lda #DHT_WAIT_RESP
    


dht_response:  ; receive response from sensor
    lda #DHT_RECV
    sta DHT_STATUS
    stz DHT_OFFSET
    lda #7
    sta DHT_BIT

dht_recv:
    ; start timer
    lda #DHT_RECV_L
    sta T1L1
    lda #DHT_RECV_H
    sta T1H1
    rts

dht_recv_read:
    ; read PA2
    lda PA2
    and #%00000001
    ldx DHT_BIT
    beq dht_recv_end
dht_recv_rot:
    rol
    dex
    bne dht_recv_rot
dht_recv_end:
    ldy DHT_OFFSET
    ora DHT_VALUES,y
    sta DHT_VALUES,y
    ; determine if 8 bits are done
    ldx DHT_BIT
    beq dht_recv_next
    rts
dht_recv_next:
    lda #7
    sta DHT_BIT
    inc DHT_OFFSET
    cmp DHT_OFF_DONE
    beq dht_display
    rts

dht_display:
    ldx #0
dht_display_:
    lda DHT_VALUES,x
    sta TO_PRINT,x
    inx
    cpx #5
    bne dht_display_
    jsr lcd_print_clear
    rts

dht_irq:
    lda DHT_STATUS
    cmp #DHT_WAIT_REQ
    beq dht_request_end
    cmp #DHT_WAIT_RESP
    beq dht_response
    cmp #DHT_RECV
    beq dht_recv
    rts