;;
  ;;  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=16F887
  include   "p16f887.inc"
  __config  _CONFIG1,  _DEBUG_OFF & _LVP_OFF & _FCMEN_OFF & _IESO_OFF & _BOR_OFF & _CPD_OFF & _CP_OFF & _MCLRE_OFF & _PWRTE_OFF & _WDT_OFF & _INTOSC
  __config  _CONFIG2,  _BOR21V & _WRT_256

  ;; -------------------------------------
  ;; DEFINES
#define         BOOTPIN   PORTC,7
USERVECT        EQU       H'100'
ISRVECT         EQU       USERVECT + H'4'
FSS             EQU       8

  ;; ERROR codes
E_OK            EQU       0
E_INV_CMD       EQU       1
E_BAD_CSUM      EQU       2
E_NOT_IMPL      EQU       3
E_FLASH_WERR    EQU       4
E_ADDR_INVALID  EQU       5
E_ADDR_PROHIB   EQU       6

  ;; CMD codes
CCMD_IDENTIFY   EQU       'i'
CMD_IDENTIFY    EQU       0

CCMD_BOOT       EQU       'b'
CMD_BOOT        EQU       1

CCMD_RESET      EQU       'r'
CMD_RESET       EQU       2

CCMD_R_FLASH    EQU       'f'
CMD_R_FLASH     EQU       3

CCMD_W_FLASH    EQU       'F'
CMD_W_FLASH     EQU       4

CCMD_R_EEPROM   EQU       'e'
CMD_R_EEPROM    EQU       5

CCMD_W_EEPROM   EQU       'E'
CMD_W_EEPROM    EQU       6

CCMD_R_CONFIG   EQU       'c'
CMD_R_CONFIG    EQU       7

CCMD_W_CONFIG   EQU       'C'
CMD_W_CONFIG    EQU       8

  ;; ...
CNT1		EQU	   H'0020'
CNT2		EQU	   H'0021'

  ;; -------------------------------------
  ;; Boot test
  org	    0
  ;; btfsc     BOOTPIN
  ;; goto      USERVECT
  goto      boot

  ;; -------------------------------------
  ;; goto user ISR
  org       4
isr
  goto      ISRVECT

  ;; -------------------------------------
  ;; Bootloader (Subroutines)
uart_tx_byte
  btfss     PIR1,TXIF
  goto      uart_tx_byte
  movwf     TXREG
  return

translate_cmd_codes
  xorlw     CCMD_IDENTIFY
  btfsc     STATUS,Z
  retlw     CMD_IDENTIFY
  xorlw     CCMD_BOOT ^ CCMD_IDENTIFY
  btfsc     STATUS,Z
  retlw     CMD_BOOT
  xorlw     CCMD_RESET ^ CCMD_BOOT
  btfsc     STATUS,Z
  retlw     CMD_RESET
  xorlw     CCMD_R_FLASH ^ CCMD_RESET
  btfsc     STATUS,Z
  retlw     CMD_R_FLASH
  xorlw     CCMD_W_FLASH ^ CCMD_R_FLASH
  btfsc     STATUS,Z
  retlw     CMD_W_FLASH
  xorlw     CCMD_R_EEPROM ^ CCMD_W_FLASH
  btfsc     STATUS,Z
  retlw     CMD_R_EEPROM
  xorlw     CCMD_W_EEPROM ^ CCMD_R_EEPROM
  btfsc     STATUS,Z
  retlw     CMD_W_EEPROM
  xorlw     CCMD_R_CONFIG ^ CCMD_W_EEPROM
  btfsc     STATUS,Z
  retlw     CMD_R_CONFIG
  xorlw     CCMD_W_CONFIG ^ CCMD_R_CONFIG
  btfsc     STATUS,Z
  retlw     CMD_W_CONFIG
  retlw     H'FF'

  ;; -------------------------------------
  ;; Bootloader (init)
boot
  ;; bank 3
  bsf       STATUS,RP0
  bsf       STATUS,RP1
  movlw     b'00001000'		; TX non-inverted, 16bit Baudrate, no auto baud detect
  ;; movlw     b'00011000'		; TX inverted, 16bit Baudrate, no auto baud detect
  movwf     BAUDCTL

  ;; bank 1
  bcf       STATUS,RP1
  movlw     b'01110000'		; set internal OSC to 8MHz
  movwf     OSCCON
  movlw     b'00100100'         ; Baudrate = High Speed, async mode, transmit enabled, 8bit
  movwf     TXSTA
  movlw     .34               	; Baudrate = 57600 (@ 8MHz) -> -0,79 % Error
  ;; movlw     .51               	; Baudrate = 38400 (@ 8MHz) -> -0,002 % Error
  ;; movlw     .103               	; Baudrate = 19200 (@ 8MHz) ->  0,16 % Error
  movwf     SPBRG
  clrf      SPBRGH

  ;; bank 0
  bcf       STATUS,RP0
  movlw     b'10010000'		; enable Serial Port, 8bit, enable continues receive, disable address detection
  movwf     RCSTA

wait_cmd
  btfsc     PIR1,RCIF
  goto      uart_rx_byte
  btfsc     RCSTA,OERR
  goto      uart_rx_oe
  goto      wait_cmd

uart_rx_oe
  bcf       RCSTA,CREN
  bsf       RCSTA,CREN
  goto      wait_cmd

uart_rx_byte
  btfsc     RCSTA,FERR
  goto      uart_rx_fe
  movf      RCREG,w             ; TODO: check parity??
				; TODO: move to input string
	;; TODO: check if command is finished and jump
	;;       to 'exec_cmd'
  call      translate_cmd_codes
  call      uart_tx_byte
  goto      wait_cmd
  goto      exec_cmd

uart_rx_fe
  movf      RCREG,w
  goto      wait_cmd

exec_cmd
	;; TODO: execute received command
  goto      wait_cmd

  ;; -------------------------------------
  ;; dummy user code
  org       USERVECT
  ;; goto      USERVECT
  bsf       STATUS,RP0
  bcf       TRISD,0
  bcf       STATUS,RP0
userloop
  movlw     b'00000001'
  xorwf     TRISD,f
  movlw     .255
  movwf     CNT1
usercnt1
  movlw     .255
  movwf     CNT2
usercnt2
  decfsz    CNT2,f
  goto      usercnt2
  decfsz    CNT1,f
  goto      usercnt1
  goto      userloop

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