ti/lcd: add support for backspace

Also, fix visual glitch on line wrap.

kernel/ti/kbd.asm

@@ -19,7 +19,7 @@
 ; *** Code ***
 
 kbdInit:
-	xor	a
+	ld	a, 1		; begin with A-Lock on
 	ld	(KBD_MODS), a
 	ret
 
@@ -31,7 +31,7 @@ kbdInit:
 ; waitForKey only go through after two actual key presses (otherwise, the user
 ; doesn't have enough time to de-press the button before the next waitForKey
 ; routine registers the same key press as a second one).
-; 
+;
 ; Sending 0xff to the port resets the keyboard, and then we have to send groups
 ; we want to "listen" to, with a 0 in the group bit. Thus, to know if *any* key
 ; is pressed, we send 0xff to reset the keypad, then 0x00 to select all groups,
@@ -84,13 +84,16 @@ kbdGetC:
 	jr	z, .loop	; yes? unsupported. loop.
 	call	.debounce
 	cp	KBD_KEY_ALPHA
-	jr	c, .end	; A < 0x80? valid char, return it.
+	jr	c, .result	; A < 0x80? valid char, return it.
 	jr	z, .handleAlpha
 	cp	KBD_KEY_2ND
 	jr	z, .handle2nd
 	jp	.loop
 .handleAlpha:
-	set	0, c
+	; Toggle Alpha bit in C. Also, if 2ND bit is set, toggle A-Lock mod.
+	ld	a, 1	; mask for Alpha
+	xor	c
+	ld	c, a
 	bit	1, c		; 2nd set?
 	jp	z, .loop	; unset? loop
 	; we've just hit Alpha with 2nd set. Toggle A-Lock and set Alpha to
@@ -101,9 +104,22 @@ kbdGetC:
 	ld	c, a
 	jp	.loop
 .handle2nd:
-	set	1, c
+	; toggle 2ND bit in C
+	ld	a, 2	; mask for 2ND
+	xor	c
+	ld	c, a
 	jp	.loop
-	
+
+.result:
+	; We have our result in A, *almost* time to return it. One last thing:
+	; Are in in both Alpha and 2nd mode? If yes, then it means that we
+	; should return the upcase version of our letter (if it's a letter).
+	bit	0, c
+	jr	z, .end		; nope
+	bit	1, c
+	jr	z, .end		; nope
+	; yup, we have Alpha + 2nd. Upcase!
+	call	upcase
 .end:
 	pop	hl
 	pop	bc
@@ -120,13 +136,20 @@ kbdGetC:
 	ret
 .debounce:
 	; wait until all keys are de-pressed
+	; To avoid repeat keys, we require 64 subsequent polls to indicate all
+	; depressed keys
 	push	af		; --> lvl 1
+	push	bc		; --> lvl 2
+.pressed:
+	ld	b, 64
 .wait:
 	xor	a
 	call	.get
 	inc	a		; if a was 0xff, will become 0 (nz test)
-	jr	nz, .wait	; non-zero? something is pressed
+	jr	nz, .pressed	; non-zero? something is pressed
+	djnz	.wait
 
+	pop	bc		; <-- lvl 2
 	pop	af		; <-- lvl 1
 	ret
 
@@ -144,9 +167,9 @@ kbdGetC:
 ; alpha table. same as .dtbl, for when we're in alpha mode.
 .atbl:
 	.db	0xfe, 0, 0, 0, 0, 0, 0, 0, 0
-	.db	0xfd, 0x0d, '"' ,'W' ,'R', 'M', 'H', 0, 0
-	.db	0xfb, '?', 0, 'V', 'Q', 'L', 'G', 0, 0
-	.db	0xf7, ':', 'Z', 'U', 'P', 'K', 'F', 'C', 0
-	.db	0xef, ' ', 'Y', 'T', 'O', 'J', 'E', 'B', 0
-	.db	0xdf, 0, 'X', 'S', 'N', 'I', 'D', 'A', KBD_KEY_ALPHA
+	.db	0xfd, 0x0d, '"' ,'w' ,'r', 'm', 'h', 0, 0
+	.db	0xfb, '?', 0, 'v', 'q', 'l', 'g', 0, 0
+	.db	0xf7, ':', 'z', 'u', 'p', 'k', 'f', 'c', 0
+	.db	0xef, ' ', 'y', 't', 'o', 'j', 'e', 'b', 0
+	.db	0xdf, 0, 'x', 's', 'n', 'i', 'd', 'a', KBD_KEY_ALPHA
 	.db	0xbf, 0, 0, 0, 0, 0, KBD_KEY_2ND, 0, 0x7f

kernel/ti/lcd.asm

@@ -153,13 +153,6 @@ lcdSendGlyph:
 	ld	a, (LCD_CURCOL)
 	call	lcdSetCol
 
-	; let's increase (and wrap) col now
-	inc	a
-	ld	(LCD_CURCOL), a
-	cp	16
-	jr	nz, .skip
-	call	lcdLinefeed
-.skip:
 	ld	b, FNT_HEIGHT
 .loop:
 	ld	a, (hl)
@@ -167,6 +160,14 @@ lcdSendGlyph:
 	call	lcdData
 	djnz	.loop
 
+	; Increase column and wrap if necessary
+	ld	a, (LCD_CURCOL)
+	inc	a
+	ld	(LCD_CURCOL), a
+	cp	16
+	jr	nz, .skip
+	call	lcdLinefeed
+.skip:
 	pop	hl
 	pop	bc
 	pop	af
@@ -240,6 +241,8 @@ lcdClrScr:
 lcdPutC:
 	cp	ASCII_LF
 	jp	z, lcdLinefeed
+	cp	ASCII_BS
+	jr	z, .bs
 	push	hl
 	call	fntGet
 	jr	nz, .end
@@ -247,3 +250,11 @@ lcdPutC:
 .end:
 	pop	hl
 	ret
+.bs:
+	ld	a, (LCD_CURCOL)
+	or	a
+	ret	z	; going back one line is too complicated.
+			; not implemented yet
+	dec	a
+	ld	(LCD_CURCOL), a
+	ret

recipes/ti84/README.md

@@ -1,6 +1,6 @@
 # TI-84+
 
-**This is a work-in-progress, this is far from complete.**
+**This is a work-in-progress**
 
 ## Recipe
 
@@ -25,7 +25,7 @@ You will start with a blank screen, it's normal, you haven't pressed the "ON"
 key yet. This key is mapped to F12 in the emulator. Once you press it, the
 Collapse OS prompt will appear.
 
-**WIP: the keyboard does nothing else than halting the CPU for now.**
+See z80e's `KEYBINDINGS.md` file for details.
 
 ## Upload to the calculator
 
@@ -51,6 +51,29 @@ Press "1" to continue.
 
 When this is done, you can press the ON button to see Collapse OS' prompt!
 
+## Usage
+
+The shell works like a normal shell, but with very tight screen space.
+
+When pressing a "normal" key, it spits the symbol associated to it depending
+on the current mode. In normal mode, it spits the digit/symbol. In Alpha mode,
+it spits the letter. In Alpha+2nd, it spits the uppercase letter.
+
+Special keys are Alpha and 2nd. Pressing them toggles the associated mode.
+Alpha and 2nd mode don't persist for more than one character. After the
+character is spit, mode reset to normal.
+
+Pressing 2nd then Alpha will toggle the A-Lock mode, which is a persistent mode.
+The A-Lock mode makes Alpha enabled all the time. While A-Lock mode is enabled,
+you have to enable Alpha to spit a digit/symbol.
+
+Simultaneous keypresses have undefined behavior. One of the keys will be
+registered as pressed. Mode key don't work by simultaneously pressing them with
+a "normal" key. The presses must be sequential.
+
+Keys that aren't a digit, a letter, a symbol that is part of 7-bit ASCII or one
+of the two mode key have no effect.
+
 [knightos]: https://knightos.org/
 [z80e]: https://github.com/KnightOS/z80e
 [mktiupgrade]: https://github.com/KnightOS/mktiupgrade