When I was in high school, the TI-85 was the shit. It was a great calculator, and someone had figured out how to install a loader that would allow you to run arbitrary native programs using some fancy hacking and installing programs into the “Custom” menu. The loader was called “ZShell.”
The TI-85 had an available serial port connector that let you transfer files to and from your computer and backup your calculator. ZShell was distributed as a backup file that once installed you could copy over individual programs in string variables.
Development was done using a Z80 cross assembler and some basic libraries and ROM calls that were distributed by the ZShell authors.
The first real program that I wrote and distributed was a password protection program called PWPROT. From the PWPROT readme file:
+-----------+
| Overview: |
+-----------+
This program allows the user to implement a password protection scheme
for the Texas Instrument TI-85 graphing calculator. The password can be
up to 8 characters long, uppercase alphabet only.
+--------+
| Usage: |
+--------+
To run the program press the custom menu key. This should show Zshell as
Custom Menu number 1. Select it with the f1 key. From the menu choose
pwprot. The program will prompt the user for a menu of changing passwords,
shutting down, or quit.
To change passwords select option 2, by hitting the 2 button.
The calculator will prompt you for the password, enter it bytyping it on
the calculator keys. When you have completed the password hit enter. The
calculator will then print the password you have entered and ask if it is
correct or not. If it is correct select 1, and the calculatorwill display
password changed. If you have have not entered the password correctly
choose option 2, and the calculator will display "Password Not Changed"
and return to the main menu.
To shut down and use the password protection feature choose option
1 from the main menu. The calculator will promptly turn itself off. When
the on key is pressed pwprot will prompt you to enter a password if it is
correct the calculator will return to normal operating mode. If it is
incorrect, the calculator will turn itself off again.
Below is the source code to PWPROT, my password protection program.
;+--------------------------------------------
;| Password Protection For TI-85, Via Zshell
;| Chris Bowron / Digital Dreamland 1996
;| ai150@detroit.freenet.org
;|
;| "When Privacy Is Outlawed, Only Outlaws
;| Will Have Privacy"
;|
;| "Living is easy with eyes closed,
;| Misunderstanding all you see"
;| John Lennon
;|
;| "Anyone who says they can see through
;| women is missing alot"
;| Groucho Marx
;+--------------------------------------------
;|Don't laugh, this is my first 'real' program
;+--------------------------------------------
;| Last Modification Jan 24, 1996 Circa 9:30 PM
;+----------------------------------------------
;| To Do List:
;| Change Password From Program (e.g. Choose Shutdown or Change PW) - Done
;| Distribute (String & Source) - In Progress
;| Fathom How The Hell It Actually Works - Slowly, but Surely
;| Self Encrypting???? - Pipe Dream 🙂
;| Makes Wads Of Cash - Working on It
;|
#INCLUDE "TI-85.H"
#define RECALC ld hl,ZS_BITS \ set 0,(hl)
#define WARPOUT ld hl,ZS_BITS \ set 1,(hl)
TEXT_X = $800D
TEXT_Y = $800C
.org 0
.db "¿¿Â PW Protect v1.24",0
;+------
;| Start Here Buddy,
;+------
ProgStart:
ROM_CALL(ClearLCD)
ld a,0
ld (text_x),a
ld (text_y),a
ld hl, (PROGRAM_ADDR)
ld de, MenuStr
add hl, de
ROM_CALL(D_ZT_STR)
CALL_(WaitKey)
cp K_EXIT
jr z, OutOfHere
cp K_3
jr z, Menu3
cp K_1
jr z, Menu1
cp K_2
jr z, Menu2
jr ProgStart
Menu1:
CALL_(ShutDown)
jr OutOfHere
Menu2:
CALL_(ChangePassword)
jr ProgStart
Menu3:
OutOfHere:
CALL_(DispCorrect)
CALL_(WaitKey)
RECALC ;Recalculate CheckSum
WARPOUT
ret
;+-----
;| Change Password
;+-----
ChangePassword:
ROM_CALL(ClearLCD)
ld hl, (PROGRAM_ADDR)
ld de, CurrentStr
add hl, de
ld a,0
ld (text_x),a
ld a,4
ld (text_y),a
ROM_CALL(D_ZT_STR)
CALL_(GetPassword)
CALL_(CheckPW)
cp 0
jr nz, WrongPW
ROM_CALL(ClearLCD)
ld hl, (PROGRAM_ADDR)
ld de, NewStr
add hl, de
ld a,0
ld (text_x),a
ld a,4
ld (text_y),a
ROM_CALL(D_ZT_STR)
CALL_(GetPassword)
ROM_CALL(ClearLCD)
ld a,0
ld (text_x),a
ld (text_y),a
ld hl, (PROGRAM_ADDR)
ld de, DummyStr
add hl, de
ROM_CALL(D_ZT_STR)
ld a,0
ld (text_x),a
ld a,1
ld (text_y),a
ld hl, (PROGRAM_ADDR)
ld de, YesNoStr
add hl, de
ROM_CALL(D_ZT_STR)
PWCKeyLoop:
CALL_(WaitKey)
cp K_1
jr z, ChangeIt
cp K_2
jr z, DontDoIt
cp K_EXIT
jr z, DontDoIt
jr PWCKeyLoop
ChangeIt:
CALL_(DummyStr2PWStr)
jr CPWExit
DontDoIt:
ld hl, (PROGRAM_ADDR)
ld de, NoChangeStr
add hl, de
ROM_CALL(D_ZT_STR)
CALL_(WaitKey)
jr CPWExit
WrongPW:
CALL_(DispWrong)
CALL_(WaitKey)
CPWExit:
ret
;+----
;| Copy Password From DummyStr to PWStr
;+----
DummyStr2PWStr:
ld hl, (PROGRAM_ADDR)
ld de, DummyStr
add hl, de ; HL Points To DummyStr
ex de, hl ; DE Points To DummyStr
ld hl, (PROGRAM_ADDR)
ld bc, PWStr
add hl, bc ; HL Points To PWStr
ld b, 8 ; 8 Chars For PW
CILoop:
ld a, (de)
ld (hl), a ; PWStr[8-b] = DummyStr[8-b]
inc hl
inc de
djnz CILoop
ld hl, (PROGRAM_ADDR)
ld de, ChangeStr
add hl, de
ROM_CALL(D_ZT_STR)
CALL_(WaitKey)
ret
;+-----
;| Shut Down Calculator, Prompting For PW When Turned ON
;+-----
ShutDown:
ROM_CALL(ClearLCD)
CALL_(DispInfo)
MajorLoop:
CALL_(PowerDown)
CALL_(GetPassWord)
CALL_(CheckPW)
cp 0
jr z, CorrectPW
WrongStinkingPW:
CALL_(DispWrong)
CALL_(WaitKey)
ROM_CALL(ClearLCD)
CALL_(DispInfo)
jr MajorLoop
CorrectPW:
ReturnCalc:
ret
;+------
;| Display Program Info
;+------
DispInfo:
ld a, 0
ld (text_x),a
ld (text_y),a
ld de, InfoStr
ld hl, (PROGRAM_ADDR)
add hl, de
ROM_CALL(D_ZT_STR)
ret
;+------
;| Display Incorrect PW Info
;+------
DispWrong:
ROM_CALL(ClearLCD)
ld a, 0
ld (text_x),a
ld (text_y),a
ld de, WrongPWStr
ld hl, (PROGRAM_ADDR)
add hl, de
ROM_CALL(D_ZT_STR)
ret
;+------
;| Display Correct PW Info
;+------
DispCorrect:
ROM_CALL(ClearLCD)
ld a, 0
ld (text_x),a
ld (text_y),a
ld de, CorrectPWStr
ld hl, (PROGRAM_ADDR)
add hl, de
ROM_CALL(D_ZT_STR)
ret
;+------
;| Wait Until Keypressed (A = Scan code)
;+------
WaitKey:
call get_key
cp K_NOKEY
jr z, WaitKey
ret
;+------
;| Wait Till Key Pressed Or LCD Is On / Currently Unused
;+------
;WaitOn:
;
; in a, (3)
;
; bit 1, a ; Is LCD On?
; jr nz, ExitWO
;
; bit 0, a
; jr nz, ExitWO ; Has On Been Pressed?
;
; bit 3, a
; jr z, ExitWO ; Is On Pressed NOW...
;
; call GET_KEY
; cp 0
; jr z, WaitOn
;
;ExitWO:
;
; ret
;
;+------
;| Shut Down Calculator
;+------
PowerDown:
DI
ld a, 00000001b
OUT ($03),A
;76543210
ld a, 00000000
; ||||
; ||++---Low Resistance
; ++---- 10 Byte Buffer
out (4),a
EX AF,AF' ; 4B59
EXX ; 4B5A
;ld a, $40 ; Doesn't work correctly
;out (6),a
EI
HALT
TurnOn:
;DI
ld a, $16 ; Normal Buffer Mode
out (4),a
ld a, $41
out (6),a
ld a, 00001011b ;LCD On
out (3),a
;EI
ret
;+------
;| Get Password From Calculator
;+------
GetPassWord:
ld a, 0
ld (text_x),a
ld a, 5
ld (text_y),a
ld hl, (PROGRAM_ADDR)
ld de, PromptStr
add hl,de
ROM_CALL(D_ZT_STR) ; print prompt
CALL_(GetString) ; DummyStr = Entered Password
ret
;+------
;| Get String Into DummyStr
;+------
GetString:
ld hl,(PROGRAM_ADDR)
ld de, DummyStr
add hl, de ; HL Points To DummyStr
push hl ; start of DummyStr
ld b, 8 ; Zero Out DummyStr
FillLoop:
inc hl
ld a,0
ld (hl), a
djnz FillLoop
pop hl
GSLoop:
push hl
ld a, 'Ú'
ROM_CALL(TX_CHARPUT)
ld hl, (TEXT_X)
dec hl
ld (TEXT_X), hl
pop hl
CALL_(GetLetter)
cp 0
jr z, HopOut
cp K_EXIT
jr z, HopOut
ld (hl),a
inc b
inc hl
ld a, b ; Check If 8 Chars entered
cp 8
jr nz, GSLoop
HopOut:
ld a, 0
ld (hl),a ; Set to Null
ret
;+----
;| Check if DummyStr=PWStr
;+----
CheckPW:
ld hl, (PROGRAM_ADDR)
ld de, DummyStr
add hl, de
ex de, hl ; DE Points To DummyStr
ld hl, (PROGRAM_ADDR)
ld bc, PWStr
add hl, bc ; HL Points To PWStr
CheckLoop:
ld a, (hl) ; HL to PWStr
ld b, a ; DE to DummyStr
ex de, hl ; Switch
ld a,(hl) ; HL to DummyStr
ex de, hl ; DE Points to PWStr
cp b
jr nz, NotEqual
Equal: ; DE[n] = HL[n]
inc de ; increase pointers
inc hl
cp 0 ; If Zero Return 0
jr nz, CheckLoop ; A = 0
; EOS
ld b,0
jr BaBoom
NotEqual:
ld b, 1 ; If Not = Then Return 1
BaBoom:
ld a,b ; ret b as acc
ret
;+-------
;| Get One Letter & Translate
;| This routine and LetterTable from Magnus Hagander's Texanoid Game
;+-------
GetLetter:
push hl
push bc
ld hl,(PROGRAM_ADDR)
ld de,LetterTable-1 ;Point to one before, since we always inc once
add hl,de ;HL now points right
ConvertLoop:
push hl
CALL Get_Key ;ACC holds key
pop hl
cp K_EXIT ;temp
jr z, Shazam
cp 0
jr z,ConvertLoop
push hl ;save away...
ld b,a
ld c,0
ConversionLoop:
inc hl
djnz ConversionLoop ;After this, we have the correct offset...
ld a,(HL)
pop hl
cp 255
jr z,ConvertLoop ;Invalid key
ROM_CALL(TX_CHARPUT) ;Show the char
Shazam:
pop bc
pop hl
ret ;Value is in acc
;+-------
;| Stuff That's Useful
;+-------
InfoStr:
;123456789012345678901 ;
.db " Password Protect "
.db " Digital Dreamland "
.db " hristopher owron "
.db 0 ; End String
MenuStr:
;123456789012345678901
.db " ¿¿Â Password Protect"
.db " Ver 1.24 "
.db "1. Shut Down "
.db "2. Change Password "
.db "3. Quit "
.db 0
NewStr:
.db "New ",0
CurrentStr:
.db "Current ",0
PromptStr:
.db "Password:",0
PWStr: ;1234567
.db 'B','O','O',0,0,0,0,0,0 ; Allow for 8 chars + Null Byte
DummyStr:
.db 0,0,0,0,0,0,0,0,0 ; Temp Work Space
YesNoStr:
;123456789012345678901
.db " Is This Correct? "
.db "1. Yes "
.db "2. No "
.db 0
ChangeStr:
.db "Password Changed",0
NoChangeStr:
.db "Password Not Changed",0
WrongPWStr:
.db "Incorrect PW!",0
CorrectPWStr:
;123456789012345678901
.db " Thank You For Using " ;1
.db " DDL Products " ;2
.db " ¿¿Â MCMXCVI " ;3
.db " " ;4
.db " [Share And Enjoy] " ;5
.db "ai150@ " ;6
.db "detroit.freenet.org " ;7
.db 0
LetterTable: ; For converting keys into letters
.db 255,255,255,255
.db 255,255,255,255
.db 000,'X','T','O'
.db 'J','E',255,255
.db ' ','W','S','N'
.db 'I','D',255,255
.db 'Z','V','R','M'
.db 'H','C',255,255
.db 'Y','U','Q','L'
.db 'G','B',255,255
.db 255,255,'P','K'
.db 'F','A',255,255
.db 255,255,255,255
.db 255,255,255,255
.end
If only TI had an app store in 1996, you could have made those Wads of Cash