fix keyboard driver to work on real hardware (hopefully)

kernel/nintendo/keyboard.s

@@ -79,6 +79,13 @@ key_delay:		.byte $00
 
 ; TODO: check if a keyboard is actually connected.
 
+; burn some cycles to give the keyboard time to settle.
+keyb_delay:
+		ldy #10
+	-	dey
+		bne -
+		rts
+
 ; interrupt routine, that scans for keys
 keyb_scan:
 		; our current key table offset encodes where we are in the scanning process.
@@ -101,6 +108,7 @@ read_keyboard:
 		; reset the keyboard to the 0th row, 0th column.
 		lda #$05
 		sta JOYPAD1
+		jsr keyb_delay ; this may not be strictly necessary but it's safer and only wastes a few cycles.
 		; reset keytab_offset to 0
 		ldx #0
 		stx keytab_offset
@@ -115,6 +123,7 @@ get_nibble:
 		; always set the keyboard enable bit.
 		ora #%00000100
 		sta JOYPAD1
+		jsr keyb_delay
 
 		; read 4 bits of key data from the keyboard.
 		lda JOYPAD2

kernel/nintendo/keyboard_init.s

@@ -16,26 +16,41 @@
 		;; initialize and install keyboard scanning routine
 keyboard_init:
 		; check that a keyboard is attached.
-
 		; reset the keyboard to the 0th row, 0th column.
 		lda #$05
 		sta JOYPAD1
 
-		; toggle the column select bit until we reach the keyless 10th row.
+		; give the keyboard some time to reset.
+		nop
+		nop
+		nop
+		nop
+		nop
+		nop
+
+		; toggle the column select bit until we reach the last column of the 9th row.
+		ldx #9
+	-	lda #$04
+		sta JOYPAD1
+		jsr _delay
 		lda #$06
-		ldx #$04
-		ldy #18
-	-	sta JOYPAD1
-		stx JOYPAD1
-		dey
+		sta JOYPAD1
+		jsr _delay
+		dex
 		bne -
 
+		; select the keyless 10th row.
+		lda #$04
+		sta JOYPAD1
+		jsr _delay
+
 		; check that the keyboard responds correctly to enable/disable signals.
 		lda JOYPAD2
 		and #$1e
 		eor #$1e
 		bne _printmsg ; branch on error
 		sta JOYPAD1
+		jsr _delay
 		lda JOYPAD2
 		and #$1e
 		bne _printmsg ; branch on error
@@ -60,8 +75,15 @@ _printmsg:
 		bne  -
 	+	rts
 
+; burn some cycles to give the keyboard time to settle.
+_delay:
+		ldy #10
+	-	dey
+		bne -
+		rts
+
 _startmsg:
-		.text "Family BASIC Keyboard module version 0.3"
+		.text "Family BASIC Keyboard module version 0.4"
 		.byte $0a
 _errormsg:
 		.text "No Keyboard"