; ***************************************************************************
; copyright   : (C) 2025 by Martin Preuss
; email       : martin@libchipcard.de
;
; ***************************************************************************
; * This file is part of the project "AqHome".                              *
; * Please see toplevel file COPYING of that project for license details.   *
; ***************************************************************************


.equ UARTSOFT_WAITFORSYNCSTART = 200


; ***************************************************************************
; code


.cseg





uartSoftWaitAndReadSyncByte:
; wait for begin of startbit
  ldi r24, LOW(UARTSOFT_WAITFORSYNCSTART)
  ldi r25, HIGH(UARTSOFT_WAITFORSYNCSTART)
uartSoftWaitAndReadSyncByte_loop0:
    sbis COM_DATA_INPUT, COM_DATA_PIN
      rjmp uartSoftWaitAndReadSyncByte_gotStartBit
    sbiw r25:r24, 1
  brne uartSoftWaitAndReadSyncByte_loop0
uartSoftWaitAndReadSyncByte_error:                     ; timeout
  clc
  ret

uartSoftWaitAndReadSyncByte_gotStartBit:
  clr r25
  clr r24
; count cycles while DATA low (count length of startBit)
uartSoftWaitAndReadSyncByte_loopLow:                   ; 5 cycles per loop +3 cycles to leave loop
    sbic COM_DATA_INPUT, COM_DATA_PIN                  ; +2 (skip)/+1 (no skip)
      rjmp uartSoftWaitAndReadSyncByte_startDataBit1   ; +0 (skip) / +2 (no skip)
    adiw r25:r24, 1                                    ; +1
  brne uartSoftWaitAndReadSyncByte_loopLow             ; +2
  rjmp uartSoftWaitAndReadSyncByte_error

uartSoftWaitAndReadSyncByte_startDataBit1:
  clr r25
  clr r24
  ldi r17, 4
uartSoftWaitAndReadSyncByte_loopData:
  ; count cycles while DATA high (count length of dataBit)
  uartSoftWaitAndReadSyncByte_loopDataHigh:              ; 5 cycles per loop +3 cycles to leave loop
      sbis COM_DATA_INPUT, COM_DATA_PIN                  ; +2 (skip)/+1 (no skip)
        rjmp uartSoftWaitAndReadSyncByte_startLowDataBit ; +0 (skip) / +2 (no skip)
      adiw r25:r24, 1                                    ; +1
    brne uartSoftWaitAndReadSyncByte_loopDataHigh               ; +2
  ; too long LOW
    rjmp uartSoftWaitAndReadSyncByte_error
  uartSoftWaitAndReadSyncByte_startLowDataBit:
  ; count cycles while DATA low (count length of dataBit)
uartSoftWaitAndReadSyncByte_loopDataLow:                 ; 5 cycles per loop +3 cycles to leave loop
      sbic COM_DATA_INPUT, COM_DATA_PIN                   ; +2 (skip)/+1 (no skip)
        rjmp uartSoftWaitAndReadSyncByte_startHighDataBit ; +0 (skip) / +2 (no skip)
      adiw r25:r24, 1                                     ; +1
    brne uartSoftWaitAndReadSyncByte_loop4                ; +2
  ; too long LOW
    rjmp uartSoftWaitAndReadSyncByte_error
uartSoftWaitAndReadSyncByte_startHighDataBit:
    dec r17
  brne uartSoftWaitAndReadSyncByte_loopData 
; calc average (8 values)
  lsr r25  ; /2
  ror r24
  lsr r25  ; /4
  ror r24
  lsr r25  ; /8
  ror r24
  sec
  ret
; @end








uartSoftReceiveByte:
; wait for begin of startbit
  ldi r24, LOW(UARTSOFT_WAITFORSYNCSTART)
  ldi r25, HIGH(UARTSOFT_WAITFORSYNCSTART)
uartSoftReceiveByte_waitForBeginOfStartBit:
    sbis COM_DATA_INPUT, COM_DATA_PIN
      rjmp uartSoftReceiveByte_gotBeginOfStartBit
    sbiw r25:r24, 1
  brne uartSoftReceiveByte_waitForBeginOfStartBit
uartSoftReceiveByte_error:                             ; timeout
  clc
  ret

uartSoftReceiveByte_gotBeginOfStartBit:
  clr r25
  clr r24
; count cycles while DATA low (count length of startBit)
uartSoftReceiveByte_waitForEndOfStartBit:              ; 5 cycles per loop
    sbic COM_DATA_INPUT, COM_DATA_PIN                  ; +2 (skip)/+1 (no skip)
      rjmp uartSoftReceiveByte_gotEndOfStartBit        ; +0 (skip) / +2 (no skip)
    adiw r25:r24, 1                                    ; +1
  brne uartSoftWaitAndReadSyncByte_loopLow             ; +2
  rjmp uartSoftReceiveByte_error
uartSoftReceiveByte_gotEndOfStartBit:
; r25:r24=counter equivalent for length of startbit
  clr r16
  ldi r17, 8
uartSoftReceiveByte_bitLoop:
  ; TODO: receive 8bits, wait for start of endbit
  
  ret









uartSoftCountDataLow:                                  ; 5 cycles per loop +5 cycles outside (+3 cycles RCALL)
    sbic COM_DATA_INPUT, COM_DATA_PIN                  ; +2 (skip)/+1 (no skip)
      rjmp uartSoftCountDataLow_ok                     ; +0 (skip) / +2 (no skip)
    adiw r25:r24, 1                                    ; +1
  brne uartSoftCountDataLow                            ; +2
  clc
  ret
uartSoftCountDataLow_ok:
  sec
  ret
; @end



uartSoftCountDataHigh:                                 ; 5 cycles per loop +5 cycles outside (+3 cycles RCALL)
    sbis COM_DATA_INPUT, COM_DATA_PIN                  ; +2 (skip)/+1 (no skip)
      rjmp uartSoftCountDataHigh_ok                    ; +0 (skip) / +2 (no skip)
    adiw r25:r24, 1                                    ; +1
  brne uartSoftCountDataHigh                           ; +2
  clc
  ret
uartSoftCountDataHigh_ok:
  sec                                                  ; +1
  ret                                                  ; +4
; @end



uartSoftWaitBitTime:                                   ; 5 cycles per loop +5 cycles outside (+3 cycles RCALL)
uartSoftWaitBitTime_loop:
    nop                                                ; +1
    nop                                                ; +1
    sbiw r25:r24, 1                                    ; +1
  brne uartSoftWaitBitTime_loop                        ; +2
  nop                                                  ; +1
  ret                                                  ; +4
; @end