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J. Calhoun
Joined: 19 Nov 2006
Posts: 71
Location: San Jose, CA
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 Posted: Jan Sat 06, 2007 1:15 am Post subject: Keyboard Interfacing Frustrations |
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Well, I'm stymied. I've been trying to solve this problem all week to no avail so I'm going to try to ellicit experienced help.
In short, I've written code for the ATMEGA8515 that should scan an AppleIIe keyboard and output ASCII. In the simulator (AVRStudio4) it looks good. When I download the code to the chip .... it doesn't work.
Well, almost ... some of the keys work, just not all. It seems one row is off. The IIe keyboard is an 8 x 10 matrix. But the 8 keys in this column (?, O, L, 9, ", -, }, rt. cursor) report the wrong row.
I know the row is wrong because I quadruple checked it with a continuity tester. And furthermore, the same assumptions worked with my Arduino-based attempt to interface the IIe with the Replica I.
I've changed the PORT's around, I've rewritten the code several times in different ways, and it always behaves the same way; most of the keys work but for the 8 in the one column.
Since I'm new to AVR assembler, I thought maybe someone experienced will see a problem in my code. There is no debouncing, SHIFT key support, STROBING and other refinements, but that should make the code a little simpler to digest. And in any event, even this basic functionality is broken.
I looked at your code, Vince, for the PS/2 interface and made some changes to my code based on yours, but still to no luck.
I have PORTD going to the LED's on the STK500 for debugging. This is how I am checking the ROW values and determining they are wrong.
| Code: | ;Apple IIe Keyboard to ASCII Interface
;
; PORT B represents the 8 rows of the keyboard
; PORT A and part of PORT C represent inputs for the columns (and EVENTUAL modifiers)
; PORT D is used as the ASCII output (for debugging right now)
.include "8515def.inc" ; Includes the 8515 definitions file
.def temp = R16 ; Temp var
.def keyrow = R17 ; Row we are scanning
.def temp2 = R18 ; Another temp var
.def keycode = R19 ; Keyboard row/column code
// ------------------------------ reset
reset:
ldi temp, high(RAMEND)
out SPH, temp
ldi temp, low(RAMEND) ; Set up stack pointer
out SPL, temp
ldi temp, 0xFF ; PORTB outputs.
out DDRB, temp
ldi temp, 0x00 ; PORTA inputs.
out DDRA, temp
ldi temp, 0xFF ; Enable pull-up resitors for PORTA
out PORTA, temp
ldi temp, 0xF0 ; PORTC inputs.
out DDRC, temp
ldi temp, 0xFF ; Enable pull-up resitors for PORTC
out PORTC, temp
ldi temp, 0xFF ; PORTD outputs.
out DDRD, temp
loop:
rcall scan_keyboard
; out PORTD, keycode
rjmp loop
// ------------------------------ scan_keyboard
scan_keyboard:
ldi keyrow, 0x00
ldi keycode, 0xFF ; Indicate no key with 0xFF
ldi temp2, 0xFE
scan_new_row:
out PORTB, temp2 ; Drop low the row we are scanning.
sbis PINA, 0x00 ; Skip if column 0 set
ldi keycode, 0x01
sbis PINA, 0x01 ; Skip if column 1 set
ldi keycode, 0x02
sbis PINA, 0x02 ; Skip if column 2 set
ldi keycode, 0x03
sbis PINA, 0x03 ; Skip if column 3 set
ldi keycode, 0x04
sbis PINA, 0x04 ; Skip if column 4 set
ldi keycode, 0x05
sbis PINA, 0x05 ; Skip if column 5 set
ldi keycode, 0x06
sbis PINA, 0x06 ; Skip if column 6 set
ldi keycode, 0x07
sbis PINA, 0x07 ; Skip if column 7 set
ldi keycode, 0x08
sbis PINC, 0x00 ; Skip if column 8 set
ldi keycode, 0x09
sbis PINC, 0x01 ; Skip if column 9 set
ldi keycode, 0x0A
cpi keycode, 0xFF ; Did we find a key
brne got_key
row_complete:
inc keyrow
cpi keyrow, 0x08 ; See if we have completed the last row
breq scan_done
rol temp2 ; Not done scanning, rotate row
rjmp scan_new_row
got_key:
out PORTD, keyrow ; TEMP - TESTING - WRONG ROW HERE FOR SOME KEYS
dec keycode ; Was 1-based, make 0-based.
cpi keyrow, 0x00 ; If on row 0, we're done.
breq scan_done ; keycode indicates offset into ASCII table
ldi temp, 0x0A ; Otherwise, add 0x0A offset for each row
add_row_offset: ; keyocde will then represent offset into ASCII table
add keycode, temp
dec keyrow
cpi keyrow, 0x00
brne add_row_offset
scan_done:
ret
code_2_ASCII:
.db '?', '>', 'N', 'B', 'V', 'C', 'X', '<', 'M', 'Z'
.db 'O', 'I', 'Y', 'R', 'E', 'W', 'Q', 'U', 'T', 0x09
.db 'L', ':', 'G', 'F', 'H', 'S', 'D', 'K', 'J', 'A'
.db '9', '8', '6', '4', '3', '2', '1', '7', '5', 0x1B
.db 0x22, 0x20, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0D, 0x00
.db '-', '0', 0x00, 0x00, 0x00, 0x00, 0x00, '=', 0x5C, 0x00
.db '}', '{', 0x00, 0x00, 0x00, 0x00, 0x00, 'P', '~', 0x00
.db 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 |
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J. Calhoun
Joined: 19 Nov 2006
Posts: 71
Location: San Jose, CA
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| Posted: Jan Sun 07, 2007 5:06 am Post subject: |
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I give up, sort of. If the keys want to be in different rows, I'm going to oblige them. I still don't know what is going on though.
I changed the ASCII values in my table to map to what the ATMEGA is seeing and sure enough I can type to the Replica I. All characters.
I see though that when I send a tilde (~) the Replica I sees a caret (^). Is that right? Maybe the Apple I didn't know these characters? And the bar (|) character is substituted as well. And a few others too (maybe the curly braces and perhaps one other key?).
I'll be using ExpressPCB to make up a few boards soon.... |
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