;;
  ;;  spreadspace pic utils
  ;;
  ;;
  ;;  Copyright (C) 2011 Christian Pointner <equinox@spreadspace.org>
  ;;                         
  ;;  This file is part of spreadspace pic utils.
  ;;
  ;;  spreadspace pic utils is free software: you can redistribute it and/or modify
  ;;  it under the terms of the GNU General Public License as published by
  ;;  the Free Software Foundation, either version 3 of the License, or
  ;;  any later version.
  ;;
  ;;  spreadspace pic utils is distributed in the hope that it will be useful,
  ;;  but WITHOUT ANY WARRANTY; without even the implied warranty of
  ;;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  ;;  GNU General Public License for more details.
  ;;
  ;;  You should have received a copy of the GNU General Public License
  ;;  along with spreadspace pic utils. If not, see <http://www.gnu.org/licenses/>.
  ;;
  ;; -------------------------------------
  ;; PREAMBLE

  LIST      p=16F1847
  include   "p16f1847.inc"
  __config  _CONFIG1,  _FOSC_INTOSC & _WDTE_OFF & _PWRTE_OFF & _MCLRE_ON & _CP_OFF & _CPD_OFF & _BOREN_OFF & _CLKOUTEN_OFF & _IESO_OFF & _FCMEN_OFF
  __config  _CONFIG2,  _WRT_OFF & _PLLEN_OFF & _STVREN_OFF & _BORV_LO & _LVP_OFF


  ;; -------------------------------------
  ;; DEFINES
  ;; constants
BUF_STARTH    EQU 020h
BUF_STARTL    EQU 000h
BUF_ENDH      EQU 023h
BUF_ENDL      EQU 0BFh

  ;; I/O Pins
;; PortA
C1m           EQU .0
C2p           EQU .1
AMP_OUT       EQU .2
ADC_IN        EQU .3
CCP4          EQU .4
;; PortB
SDI           EQU .1
SDO           EQU .2
INT           EQU .3
SCK           EQU .4
CS            EQU .5
FILTER_EN     EQU .7

  ;; variables
  ;;  all Pages
CNT0          EQU H'0070'
CNT1          EQU H'0071'
CNT2          EQU H'0072'
TMP           EQU H'0073'

FLAGS         EQU H'007F'

    ;; bits
;; FLAGS
UNDERRUN      EQU .0
OVERRUN       EQU .1
  
  ;; -------------------------------------
  ;; OFFSET
  org	      .0
  goto      init

  ;; -------------------------------------
  ;; Interrupts
  org       .4
  movlb     b'00000000'
  btfsc     PIR1,SSP1IF
  goto      int_spi
  retfie

int_spi
  bsf       PORTA,7
  bcf       PIR1,SSP1IF
  movlb     b'00000100'
  movf      SSP1BUF,w
  incf      TMP,f
  movf      TMP,w
  movwf     SSP1BUF
  movlb     b'00000000'
  bcf       PORTA,7
  retfie

  ;; -------------------------------------
  ;; SUBROUTINES
wbuf_reset
  movlw     BUF_STARTH
  movwf     FSR0H
  movlw     BUF_STARTL
  movwf     FSR0L
  bcf       FLAGS,OVERRUN
  return

  ;; -------------------
wbuf_next
  btfsc     FLAGS,UNDERRUN
  goto      wbuf_move_ptr

  movf      FSR1H,w
  xorwf     FSR0H,w
  btfss     STATUS,Z
  goto      wbuf_move_ptr

  movf      FSR1L,w
  xorwf     FSR0L,w
  btfss     STATUS,Z
  goto      wbuf_move_ptr

  bsf       FLAGS,OVERRUN
  return

wbuf_move_ptr
  bcf       FLAGS,UNDERRUN
  addfsr    FSR0,1

  movf      FSR0H,w
  sublw     BUF_ENDH
  btfss     STATUS,C
  goto      wbuf_wraparound
  btfss     STATUS,Z
  return
  movf      FSR0L,w
  sublw     BUF_ENDL
  btfsc     STATUS,C
  return

wbuf_wraparound
  movlw     BUF_STARTH
  movwf     FSR0H
  movlw     BUF_STARTL
  movwf     FSR0L
  return


  ;; -------------------
rbuf_reset
  movlw     BUF_STARTH
  movwf     FSR1H
  movlw     BUF_STARTL
  movwf     FSR1L
  bsf       FLAGS,UNDERRUN

  ;; -------------------
rbuf_next
  btfsc     FLAGS,OVERRUN
  goto      rbuf_move_ptr

  movf      FSR0H,w
  xorwf     FSR1H,w
  btfss     STATUS,Z
  goto      rbuf_move_ptr

  movf      FSR0L,w
  xorwf     FSR1L,w
  btfss     STATUS,Z
  goto      rbuf_move_ptr

  bsf       FLAGS,UNDERRUN
  return

rbuf_move_ptr
  bcf       FLAGS,OVERRUN
  addfsr    FSR1,1

  movf      FSR1H,w
  sublw     BUF_ENDH
  btfss     STATUS,C
  goto      rbuf_wraparound
  btfss     STATUS,Z
  return
  movf      FSR1L,w
  sublw     BUF_ENDL
  btfsc     STATUS,C
  return

rbuf_wraparound
  movlw     BUF_STARTH
  movwf     FSR1H
  movlw     BUF_STARTL
  movwf     FSR1L
  return

  ;; -------------------------------------
  ;; INIT
init
  ;; BANK 4
  movlb     b'00000100'
  movlw     b'01000000'
  movwf     SSP1STAT
  movlw     b'00010000'
  movwf     SSP1CON3
  movlw     b'00100100'
  movwf     SSP1CON1
  
  ;; BANK 3
  movlb     b'00000011'
  clrf      ANSELA
  clrf      ANSELB

  ;; BANK 2
  movlb     b'00000010'

  ;; BANK 1
  movlb     b'00000001'
  movlw     b'01111111'
  movwf     TRISA
  movlw     b'01110011'
  movwf     TRISB
;  movlw     b'01011000'                 ;  1 MHz
;  movlw     b'01100000'                 ;  2 MHz
  movlw     b'01101000'                 ;  4 MHz
;  movlw     b'01110000'                 ;  8 MHz
;  movlw     b'01111000'                 ; 16 MHz
  movwf     OSCCON
  movlw     b'00001000'
  movwf     PIE1
  
  ;; BANK 0
  movlb     b'00000000'
  clrf      PIR1
  movlw     b'11000000'
  movwf     INTCON

  bcf       PORTA,FILTER_EN

  bsf       PORTB,INT

  ;; -------------------------------------
  ;; MAINLOOP
main
  movlw     .255
  movwf     CNT0

outer1
  movlw     .255
  movwf     CNT1

outer
  movlw     .5
  movwf     CNT2
  
inner
  decfsz    CNT2,f
  goto      inner
  
  decfsz    CNT1,f
  goto      outer

  decfsz    CNT0,f
  goto      outer1

  movlw     b'00001000'
  xorwf     PORTB,f

  goto	    main

  ;; -------------------------------------
  ;; END
  end