' GCBOOT v8 11/13/10 - a PIC18F bootloader written in Great Cow Basic
' Code is for gcbasic (0.9 Sept 10 2010) and gpasm from gptools 0.13.7
' Compile command: gcbasic -a:"gpasm -i gcboot.asm" gcboot.gcb
' Pickit2 burn command: pk2cmd -P -T -R -M -F gcboot.hex
'
' This is a bootloader for the PIC18F2525 microcontroller, once loaded
' application code can be loaded via a serial terminal rather than having
' to use a conventional programmer. Unlike just about every other PIC18F
' bootloader, this one accepts standard microchip hex without requiring
' a specific PC app, can send code using any terminal emulator that can
' provide a short delay after each line. The present implementation does
' not support eeprom, anything in the hex file that isn't program code is
' ignored. Does not erase code that's already present, generally this
' doesn't matter and permits loading overlays or multiple apps.
'
' Configured for a 9600 baud serial port connected to the TX and RX pins
' (RC6 and RC7) using series resistors, about 1K in series with TX and
' about 22K in series with RX. The RX line should be pulled high using
' a 100K resistor to run the app when the serial port is not connected.
' Configured to flash an LED connected to RB0, if using as-is make sure
' this pin isn't grounded or connected to another device output. Runs at
' 32mhz using the internal oscillator. Bootloader starts at 0xB000.
' Edit below to configure differently. Work in progress...
'
' v0 10/24/10 - 1st working version.
' v1 10/25/10 - better error-checking, verifies jump at loc 0
'               on startup (writes only if not present),
'               hex entry no longer case-sensitive,
'               cleaned up the code a bit.
' v2 10/26/10   made compatible w/ gpasm from gputils 0.13.7,
'               added extra logic for locating past 0x8000.
' v3 10/26/10   changed flash buffer to 0x100, added wipe chip feature.
' v4 10/27/10   enabled MCLR reset pin, fixed invalid address bug.
' v5 10/29/10   modified to use 8mhz or 32mhz clock, prints config.
'    10/31/10   tweaked license info and comments, no code changes.
' v6 11/1/10    added a goto 2 after words saved from 1st 2 words.
' v7 11/10/10   added Set PLLEN off before running app.
' v8 11/13/10   added wait to avoid serial garbage w/ v7 when running app,
'               shortened messages to reduce memory usage a bit.
'
' The source code for the program is written by Terry Newton, it is provided
' as-is and without warranty of any kind. Under no circumstances shall the
' author be held liable for damages resulting from the use of the software.
' The source code itself is public domain and may be used for any purpose.
' The hex file that results from compiling this program includes libraries
' from the Great Cow Basic compiler that are Copyright Hugh Considine
' under the terms of the Lesser GNU Public License version 2.1 or later.
' GC Basic and source code is available from: http://gcbasic.sourceforge.net/
'
#chip 18F2525, 8
#config OSC = INT, BODEN = OFF, WDT = OFF, MCLRE = ON, LVP = OFF
'the following string is printed on startup to document configuration
#define CONFIGSTRING "Configuration = 32mhz MCLR LED=portb.0"
#define QUADCLOCK 1            '0 = 8mhz clock, 1 = 32mhz clock
'note.. use gpasm to locate past 0x7000 (unless using patched GCB)
#option bootloader 0xB000      'location of bootloader
#define BOOTLOADERHIGH 0xB0    'must be on 256-byte boundary
#define APPGOTO 0xBFF0         'location of first relocated goto word
#define APPGOTO2 0xBFF2        'location of second relocated goto word
#define APPGOTO3 0xBFF4        'location of 1st GOTO 2 instruction
#define APPGOTO4 0xBFF6        'location of 2nd GOTO 2 instruction
#define BUFFERHIGH 1           'location of flash buffer high/low
#define BUFFERLOW 0            'make sure it doesn't conflict w/ vars
#define USELED 1               '1 to use LED pin
#define LEDPIN portb.0         'pin for LED
#define USEXONOFF 1            '1 to (attempt to) use xon/xoff flow
#define SERPOL 1               '1 for direct connect, 0 for MAX232 etc
#define APPRUNPIN portc.7      'pin to indicate to run app (def. RX)
#define APPRUNPOL 1            'pin state to run app
#define USART_BLOCKING true
#script
if QUADCLOCK = 1 then        'if PLL enabled
 USART_BAUD_RATE = 2400      ' use 2400 to mean 9600 baud
 ONESEC = 4                  ' wait 4 s = 1 second
end if
if QUADCLOCK = 0 then        'if PLL not enabled
 USART_BAUD_RATE = 9600      'for normal 8mhz clock
 ONESEC = 1
end if
#endscript

Dim address As Word
Dim address2 As Word
Dim char As Byte
Dim temp As Byte
Dim temp1 As Byte
Dim temp2 As Byte
Dim subtemp As Byte
Dim subword As Word
Dim subword2 As Word
Dim tempword1 As Word
Dim tempword2 As Word
Dim tempword3 As Word
Dim tempword4 As Word
Dim invalid As Byte
Dim hexdigit As Byte
Dim hexbyte As Byte

Dim count As Byte
Dim byteloop As Byte
Dim checksum As Byte
Dim extadr As Byte
Dim currpage As Word
Dim newpage As Word
Dim buffcnt As Byte
Dim tblptrhsave As Byte
Dim tblptrlsave As Byte
Dim pgmword As Word
Dim pgmaddress As Word
Dim pgmaddresssave As Word
Dim bytebuffer(33)        'buffer for incoming bytes

bootstart:
IntOff           'no interrupts
Set IRCF2 on
Set IRCF1 on
Set IRCF0 on     'max frequency
#ifdef QUADCLOCK 1
Set PLLEN on     'enable PLL for 32mhz
#endif
#ifdef QUADCLOCK 0
Set PLLEN off    'in case not enabled and app enables then runs bootloader
#endif
Dir PORTA in     'all pins input
Dir PORTB in
Dir PORTC in
Dir PORTC.6 out  'except serial output
Set RXDTP SERPOL 'set polarity of serial port
Set TXCKP SERPOL
If APPRUNPIN = APPRUNPOL Then Goto run  'if serial not connected then run app

#ifdef USELED 1
 Dir LEDPIN out
 Set LEDPIN on   'flash LED to show boot mode
 wait ONESEC s        'and verify timing
 Set LEDPIN off
 wait ONESEC s
#endif
#ifndef USELED 1
 wait ONESEC s
#endif

Gosub xon: Gosub crlf
HSerPrint "=== Terry's Bootloader ===  v8 11/13/10"
Gosub crlf
HSerPrint CONFIGSTRING

menu:
#ifdef USELED 1
 Set LEDPIN on
#endif
Gosub initboot  'make sure 0-3 = jump, set extadr = 0, currpage = 0xFFFF
Gosub xon: Gosub crlf
HSerPrint "Select...":Gosub crlf
HSerPrint "P: Program (or just send)":Gosub crlf
HSerPrint "M: Examine ram":Gosub crlf
HSerPrint "V: Examine code":Gosub crlf
HSerPrint "W: Wipe chip":Gosub crlf
HSerPrint "X: Execute app":Gosub crlf
HSerPrint "> "
getcommand:
HSerReceive char
If char = 58 Then Goto directhex
If char = 80 Or char = 112 Then Gosub showentry: Goto loadhex
If char = 77 Or char = 109 Then Gosub showentry: Goto dump
If char = 86 Or char = 118 Then Gosub showentry: Goto dumpcode
If char = 87 Or char = 119 Then Gosub showentry: Goto wipechip
If char = 88 Or char = 120 Then Gosub showentry: Goto run
Goto getcommand

crlf:
HSerSend 13:HSerSend 10
Return

showentry:
HSerSend char:Gosub crlf
Return

gethexdigit:
invalid = 0
hexdigit = 0
HSerReceive char
If char > 96 And char < 103 Then char = char - 32
If char < 48 Then invalid = 1: Return
If char > 70 Then invalid = 1: Return
If char > 57 And char < 65 Then invalid = 1: Return
hexdigit = char - 48
If char >= 65 Then hexdigit = char - 55
Return

gethexbyte:
'does not get 2nd char if 1st invalid
'adds byte to checksum
hexbyte = 0
Gosub gethexdigit
subtemp = hexdigit * 16
If invalid = 0 Then
 Gosub gethexdigit
 hexbyte = subtemp + hexdigit
End If
subtemp = checksum
checksum = subtemp + hexbyte
Return

printhexdigit:
char = hexdigit + 48
If hexdigit > 9 Then char = hexdigit + 55
HSerSend char
Return

printaddress:
hexdigit = address / 4096
Gosub printhexdigit
subword = address - (hexdigit * 4096)
hexdigit = subword / 256
Gosub printhexdigit
subword2 = subword - (hexdigit * 256)
hexdigit = subword2 / 16
Gosub printhexdigit
hexdigit = subword2 - (hexdigit * 16)
Gosub printhexdigit
Return

printhexbyte:
hexdigit = hexbyte / 16
Gosub printhexdigit
subtemp = hexdigit
hexdigit = hexbyte - (subtemp * 16)
Gosub printhexdigit
Return

loadhex:
HSerReceive char
if char = 27 Then Goto menu      'abort
if char <> 58 Then Goto loadhex  'wait for ":"
directhex:
#ifdef USELED 1
 Set LEDPIN off
#endif
checksum = 0
'get count
Gosub gethexbyte
If invalid then Goto hexerror
count = hexbyte AND 127
If count > 32 Then Goto counterror
If count = 0 Then Goto terminateload
'get address
Gosub gethexbyte
If invalid then Goto hexerror
pgmaddress_h = hexbyte
Gosub gethexbyte
If invalid then Goto hexerror
[byte]pgmaddress = hexbyte
'get record type
Gosub gethexbyte
If invalid then Goto hexerror
If hexbyte = 4 Then 'handle extended address sets
 If count <> 2 Then Goto counterror
 Gosub gethexbyte
 If invalid then Goto hexerror
 Gosub gethexbyte
 If invalid then Goto hexerror
 extadr = hexbyte
 'get checksum but don't modify
 temp = checksum
 Gosub gethexbyte
 checksum = (NOT temp) + 1
 if checksum <> hexbyte Then Goto checksumerror
 Goto loadhex
End If
If hexbyte <> 0 Then Goto recordtypeerror
'if processing configs ee etc then more code is needed
'but this code only processes normal program code
If extadr <> 0 Then Goto loadhex 'ignore anything but 0
'get bytes
If (count AND 1) = 1 Then Goto counterror 'must be even
For byteloop = 1 To count
 Gosub gethexbyte
 bytebuffer(byteloop) = hexbyte
Next byteloop
'get checksum but don't modify
temp = checksum
Gosub gethexbyte
checksum = (NOT temp) + 1
if checksum <> hexbyte Then Goto checksumerror
'now program the bytes
Gosub xoff
#ifdef USELED 1
 Set LEDPIN on
#endif
byteloop = 1
pgmbyteloop:
[byte]pgmword = bytebuffer(byteloop)
pgmword_h = bytebuffer(byteloop+1)
Gosub programword
pgmaddress = pgmaddress + [word]2
byteloop = byteloop + 2
If byteloop < count Then Goto pgmbyteloop
Gosub xon
Goto loadhex

terminateload:
Gosub xoff
If currpage <> 0xFFFF Then Gosub writebuffer 'if anything loaded
Gosub xon
finishlineread:
HSerReceive char
If char = 13 Then Goto menu 
If char = 10 Then Goto menu
If char = 27 Then Goto menu
Goto finishlineread

'flow control... generally xon/xoff doesn't work with
'buffered serial cards but might help. If needed these
'subroutines can be used to add hardware flow control

xoff:
#ifdef USEXONOFF 1
HSerSend 19  'tell sender to stop sending
#endif
Return

xon:
#ifdef USEXONOFF 1
HSerSend 17  'tell sender to resume sending
#endif
Return

hexerror:
Gosub crlf
HSerPrint "Invalid hex"
Goto waitforesc

counterror:
Gosub crlf
HSerPrint "Invalid count"
Goto waitforesc

checksumerror:
Gosub crlf
HSerPrint "Checksum error"
Goto waitforesc

recordtypeerror:
Gosub crlf
HSerPrint "Invalid record"
Goto waitforesc

dump:
HSerPrint "HEX digit of block to dump: "
promptforblock:
Gosub gethexdigit
If char = 27 Then Goto menu
If invalid Then Goto promptforblock
Gosub printhexdigit: Gosub crlf
address = hexdigit * 256
for temp1 = 0 to 15
 Gosub printaddress
 HSerPrint ": "
 address2 = address
 for temp2 = 0 to 15
  fsr0h = address2_h
  fsr0l = address2
  hexbyte = indf0
  Gosub printhexbyte: HSerPrint " "
  address2 = address2 + 1
 next temp2
 Gosub crlf
 address = address + 16
next temp1
Goto menu

dumpcode:
HSerPrint "HEX Address: "
gethd1:
Gosub gethexdigit
If char = 27 Then Goto menu
If invalid Then Goto gethd1
Gosub printhexdigit
pgmaddress = hexdigit * [word]4096
gethd2:
Gosub gethexdigit
If char = 27 Then Goto menu
If invalid Then Goto gethd2
Gosub printhexdigit
pgmaddress = [word]pgmaddress + ([byte]hexdigit * [word]256)
gethd3:
Gosub gethexdigit
If char = 27 Then Goto menu
If invalid Then Goto gethd3
Gosub printhexdigit
pgmaddress = [word]pgmaddress + ([byte]hexdigit * [word]16)
gethd4:
Gosub gethexdigit
If char = 27 Then Goto menu
If invalid Then Goto gethd4
Gosub printhexdigit
pgmaddress = [word]pgmaddress + [byte]hexdigit
Gosub crlf
currpage = 0xFFFF
For temp1 = 1 To 16
 address = pgmaddress
 Gosub printaddress
 HSerPrint ": "
 For temp2 = 1 To 8
  newpage = pgmaddress / [word]64
  If newpage <> currpage Then
   currpage = newpage
   Gosub readbuffer
  End If
  fsr0h = BUFFERHIGH
  fsr0l = BUFFERLOW
  fsr0l = fsr0l + ([byte]pgmaddress AND 63)
  hexbyte = postinc0
  [byte]address = hexbyte
  hexbyte = postinc0
  address_h = hexbyte
  Gosub printaddress
  HSerSend 32
  pgmaddress = pgmaddress + [word]2
 Next temp2
 Gosub crlf
Next temp1 
Goto menu

run:
'avoid corruption of "x" when running app
#ifdef QUADCLOCK 1
Wait 200 ms    'wait for last char+crlf to be sent
Set PLLEN off  'downshift to 8mhz default clock
#endif
Goto APPGOTO   'original 2 words stored there

waitforesc:
Gosub xon
Gosub crlf
HSerPrint "Send ESC for menu "
wfeloop:
HSerReceive char
If char <> 27 Then Goto wfeloop
Gosub crlf
Goto menu

enablewrite:
asm  bcf intcon, gie 
asm  movlw 0x55
asm  movwf eecon2
asm  movlw 0xAA
asm  movwf eecon2
asm  bsf eecon1, wr
Return

readbuffer:
'reads program code into ram buffer
'currpage = current 64 byte block (word)
'tblptrhsave and tblptrlsave left pointing to currpage
fsr0h = BUFFERHIGH
fsr0l = BUFFERLOW
tblptru = 0
tblptrhsave = ([word]currpage / [word]4) AND 255
tblptrlsave = (currpage AND 3) * 64
tblptrh = tblptrhsave
tblptrl = tblptrlsave
For buffcnt = 1 To 64
asm  tblrd*+
postinc0 = tablat
Next buffcnt
Return

writebuffer:
'writes ram buffer to program space
'tblptrhsave tblptrlsave = 64 byte block to program
tblptru = 0
tblptrh = tblptrhsave
tblptrl = tblptrlsave
asm  bsf eecon1,eepgd
asm  bcf eecon1,cfgs
asm  bsf eecon1,wren
asm  bsf eecon1,free
gosub enablewrite
asm  tblrd*-
fsr0h = BUFFERHIGH
fsr0l = BUFFERLOW
For buffcnt = 1 To 64
tablat = postinc0
asm  tblwt+*
Next buffcnt
asm  bsf eecon1,eepgd
asm  bcf eecon1,cfgs
asm  bsf eecon1,wren
gosub enablewrite
asm  bcf eecon1,wren
Return

initboot:
'initialize... make sure 1st 2 words contain a jump to the bootloader so a
'partial load won't crash on reset (only write jump if it doesn't exist)
'on exit set extadr to 0, set currpage to 0xFFFF to init loading
[byte]pgmaddress = 0
[byte]pgmaddress_h = BOOTLOADERHIGH
currpage = pgmaddress / [word]64
Gosub readbuffer
fsr0h = BUFFERHIGH
fsr0l = BUFFERLOW
[byte]tempword1 = postinc0
tempword1_h = postinc0
[byte]tempword2 = postinc0
tempword2_h = postinc0      'tempword1 and tempword2 contain jump words
currpage = 0
Gosub readbuffer
fsr0h = BUFFERHIGH
fsr0l = BUFFERLOW
[byte]tempword3 = postinc0
tempword3_h = postinc0
[byte]tempword4 = postinc0
tempword4_h = postinc0      'tempword3 and tempword4 contain locs 0-3
If tempword1 <> tempword3 Or tempword2 <> tempword4 Then
 'jump to bootloader not present, put it there
 pgmaddress = 0
 pgmword = tempword1
 Gosub programrawword 'no relocation
 pgmaddress = 2
 pgmword = tempword2
 Gosub programrawword
 Gosub writebuffer
 currpage = APPGOTO3 / [word]64
 Gosub readbuffer
 pgmaddress = APPGOTO3
 pgmword = 0xEF01
 Gosub programrawword
 pgmaddress = APPGOTO4
 pgmword = 0xF000
 Gosub programrawword
 Gosub writebuffer
End If
extadr = 0
currpage = 0xFFFF
Return

programword:
'buffers/writes words to program memory
'pgmaddress = address  pgmword = word to write
'determines page, if different then writes previous page and reloads buffer
'if previous page = 0xFFFF then don't write (initial state)
'error if pgmaddress is past start of bootloader
'relocate 1st 4 bytes to APPGOTO
pgmaddresssave = pgmaddress_h
pgmaddresssave_h = 0
If pgmaddresssave >= [word]BOOTLOADERHIGH Then Goto pageerror
pgmaddresssave = pgmaddress 'save in case relocated
If pgmaddress = [word]0 Then pgmaddress = APPGOTO
If pgmaddress = [word]2 Then pgmaddress = APPGOTO2
Gosub programrawword
pgmaddress = pgmaddresssave
Return

programrawword:  'this doesn't relocate, no checking
newpage = pgmaddress / [word]64
If newpage <> currpage Then
 If currpage <> 0xFFFF Then Gosub writebuffer
 currpage = newpage
 Gosub readbuffer
 HSerSend "."
End If
fsr0h = BUFFERHIGH
fsr0l = BUFFERLOW + ([byte]pgmaddress AND 63)
asm  movff pgmword, postinc0
asm  movff pgmword_h, postinc0
Return

pageerror:
'this error occurs from within a subroutine so
'should be handled differently
#ifdef USELED 1
Set LEDPIN off
#endif
Gosub crlf
HSerPrint "Invalid address "
address = pgmaddress : Gosub printaddress
HSerPrint " ESC to reset"
Gosub crlf : Gosub xon
waittoreset:
HSerReceive char
If char <> 27 Then Goto waittoreset
Reset

wipechip:
HSerPrint "Zero ram? ":Gosub ucyconfirm
If char <> 89 Then Goto confirmerase
Gosub showentry
HSerPrint "Zeroing ram from 140 to EFF"
For address = 0x0140 to 0x0EFF
 fsr0h = address_h
 fsr0l = [byte]address
 indf0 = 0
Next address
confirmerase:
Gosub crlf
HSerPrint "Erase code? ":Gosub ucyconfirm
If char <> 89 Then Goto menu
Gosub showentry
pgmaddress = 0x0004  'don't wipe initial goto
pgmword = 0xFFFF
wipeloop:
Gosub programword
pgmaddress = pgmaddress + 2
if pgmaddress_h <> BOOTLOADERHIGH Then Goto wipeloop
Goto menu

ucyconfirm:
HSerPrint "(uppercase Y to confirm) "
HSerReceive char
Return

'end