Apple 1 keyboard Micro Switch 1974

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Hi everyone,
I'm Aurel(I'm french, please forgive my english mistakes!). I made a wire wrapping apple 1 few years ago > applethefirst

I've found this keyboard recently :
microswitch keyboard

I think it's the keyboard of the "Smithsonian" apple 1. It's a Micro Switch from 1974, but not sure which model it is.
Unfortunetly I don't know from what it was taken.
So I'm looking for informations about it (technical and historical). I'd like to know if I could use it on my replica.
For now, I've no idea how to plug it and I don't find any information on the internet.
Thanks for your help!

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speedyG's picture
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Re: Apple 1 keyboard Micro Switch 1974

hello aurel6814,
the very first attempt should be to download the schematic of the Apple II ... allthough it is not exactly the same - the principle task is comparable...
you have a matrix of switches and the only difference is that they are at the apple I a little bit more simple...
think of it as a row of 16 switches each
and 1 line to determine if the key is upper half of 16 keys from 32 keys or lower half of 16 switches from 32 keys
the next Line would be the line that determines the use of the Control-key and if the characters are controlcharacters...
the final aditional line that was used later at the apple II series was the Schift-key-line to determine if the Keys were upper case or lower case.... ( at the Apple I it was only Upper Case ! )
the determination process was executed by a so called decoderchip, that delivered the final code as one byte to the keyboard-connector.
the differences in the keyboards of those days were caused by the way the matrix was decoded and by the code that was given to the keyboard connecter.... the most common standard of keyboard-codes used in those days was the so called EBCEDI code and later at the apple II the mostly used code was the ASCII code.

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Re: Apple 1 keyboard Micro Switch 1974

Hey you finally joined AppleFritter Wink

Bienvenue....

Aurel,

To extend a bit of what Speedy said, but since I know you can "wire-wrap"

Try tracing the power, ground and 12v by figuring out the from the decoder chip on the board and it's data sheet. It looks like a nice ceramic one which ever it is. Though checking the data sheet for the decoder may just be enough to wire it up for an apple-1.

if you want to experiment before risking your computer, setup a bench supply for 5v and 12v, Next use a couple of latches to hold the output of the decoder to some LEDs with the proper resistors. You can then check the output of the keyboard's codes to make sure they work and match what the Apple-1 is expecting. If not you may have to re-map some of the bits using a few 7400 series logic chips like Wendell Sander does on his Apple-1 to generate an underscore for a rubout character.

You can then either make a custom cable or wire-wrap up a converter board once you figure it all out to hook it up to the Apple-1.

Note: All of this assumes it's a parallel keyboard.

Cheers,
Corey

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Re: Apple 1 keyboard Micro Switch 1974

hello aurel6814,
in adition to the explanations above and the points spotted out by corey986 also another hint....
because Mike Willegal made a page with info to his adaptor from PS2keyboard to apple 1 - that page
as far as i remember - contains a link to the coding of the MCU-chip used in the adaptor....
and examining that code shows at least what the normal apple 1 expects to get as input at the
keyboard plugsocket (i.e. which keys at the keyboard should generate which codes/bytes... )
so that might be an other source to examine too.....
sincerely speedyG

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Re: Apple 1 keyboard Micro Switch 1974

Thanks for the answers and your help.
Yes Corey, I'm finally here! Actually I tried to come a couple years ago but I didn't understand I had to send an email to be registered ...

So these are the chips whitch are on the pcb :
9N00/7400 > nand gate
7486 > exclusive or gate

ITT 946.5 > unknow...

and the encoder is a
2S 7422SH SW 20276, 28 pins and I have no idea what's that ! (I suppose 7422 is the datecode)I don't know what voltage it needs

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Re: Apple 1 keyboard Micro Switch 1974

Can to post or send me a closeup picture of the encoder. Maybe I can figure out what it is. Hopefully it is not a custom chip.

Cheers,
Corey

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Re: Apple 1 keyboard Micro Switch 1974

Thanks, I'm going to take some pictures.
It's definitly a parallel /ASCII keyboard. I could trace the mass, the +5v and I think what is the -12V (I compared it with the datanetics keyboard). I'm still confuse between data bit and function key.

Maybe the ITT 946.5 generate the strobe...

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Re: Apple 1 keyboard Micro Switch 1974

aurel6814 wrote:

Thanks, I'm going to take some pictures.
It's definitly a parallel /ASCII keyboard. I could trace the mass, the +5v and I think what is the -12V (I compared it with the datanetics keyboard). I'm still confuse between data bit and function key.

Maybe the ITT 946.5 generate the strobe...

Strobe (STRB) and KeyboardAcknowledge (KACKN)are Handshakesignals and are always generated/recieved from the encoderchip.
Strobe indicates to Computer I/O that a key has been struck and KeyboardAcknowledge indicates to encoderchip that the information has been picked away from CPU from the latch.

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Re: Apple 1 keyboard Micro Switch 1974

Sorry, I made a mistake >
maybe the ITT 946.5 generate the clock signal for the encoder?

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Re: Apple 1 keyboard Micro Switch 1974

Corey,
This is the picture of the encoder.

https://picasaweb.google.com/lh/photo/2ZmoKO7204oaF45QIML2RFOUa7aA8vf7Os8bbE8w_54?feat=directlink

I also made other pictures of the keyboard microswitch keyboard

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Re: Apple 1 keyboard Micro Switch 1974

Hard to tell from the pic, but is that an ASV or MSV or ???? on the top.

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Re: Apple 1 keyboard Micro Switch 1974

Hallo Corey986,
i have seen similar chips with the same ceramic top design and they had been from MSI.
This was a kind of "outfit" of single-chip-processors used from 1975 to 1981....
It seems that part of the printing has vanished by ruboff..... but MSI should be a rather sure proposal....
sincerely
speedyG

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the second part includes less friends but a lot more joy on life....

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Re: Apple 1 keyboard Micro Switch 1974

Corey986 wrote:

Hard to tell from the pic, but is that an ASV or MSV or ???? on the top.

I can't see better with my eyes! MSI seems a good guess.

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Re: Apple 1 keyboard Micro Switch 1974

"EBCEDI" ? Are you sure? I only remember EBCDIC and I can't find more about EBCEDI on Google...

(hi everybody, I'm new here, I will present myself in a message soon Wink

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Re: Apple 1 keyboard Micro Switch 1974

Aurel,

I know that this is old, but perhaps the information I have will be of use to you or others.

I believe that this keyboard is from a Texas Instruments Silent 700 terminal. In particular,
the part number matches that used by the Model 733 ASR/KSR terminal.

Bitsavers has the manual here, and the keyboard interface section starts on page 68.
http://bitsavers.org/pdf/ti/terminal/943009-9701_Silent_700_Model_733_ASR_KSR_User_Guide_Sep_1975.pdf

The 959327-0001 is an ASCII keyboard, which can be rather easily attached to an Apple 1 or
replica. The 959326-0001 version is a full upper and lowercase keyboard, and the 959325-0001
version is baudot encoded.

The Repeat, Break, Here Is, and Paper Advance buttons are all pulled up with 10k resistors
and connect to ground when pressed. Any of them can be used as a reset button, I picked the
Break button, simply because it made sense.

However, the clear screen button requires a connection to +5v when pressed, which the keyboard
does not offer as an option. You will need to find a way to invert the signal. I picked a
transistor based inverter as a method because it was simple (three parts) and could be soldered
directly to the card edge connector. If you do use an inverter, you will want to pay close
attention to the clear screen circuit as you may need to insert a diode when driving it with
an outside source other than a simple switch to +5v.

If you don't mind cutting traces on the keyboard, there appears to be a free gate on the
7400 NAND chip. It could be used along with a protection diode to connect to the clear screen
input.

Here is the pinout of the keyboard's card edge connector:

 1 Bit 6 (Data)
 2 Speed (Direct Connection to Switch Connector)
 3 Bit 1 (Data)
 4 Bit 3 (Data)
 5 Repeat (Special Function Output)
 6 Tape (Special Function Output)
 7 Tape (Special Function Output)
 8 Ground
 9 +5V Power
10 -12V Power
 A Bit 7 (Data)
 B Bit 5 (Data)
 C Bit 2 (Data)
 D
 E Break (Special Function Output)
 F Online (Direct Connection to Switch Connector)
 H Strobe Pulse
 J Here Is (Special Function Output)
 K Paper ADVance (Special Function Output)
 L Clock (For Debounce Circuit)

I have a more detailed writeup here about the cable I made as well.

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Re: Apple 1 keyboard Micro Switch 1974

Well good timing on yor part. I just bought one of these last night from someone. I've been looking for a while for a dual cassette TI silent. When it arrives and I start restoring it, I'll pull the keyboard and compare it to his pic just to make sure that is the exact one. I'll repost to this thread when I do. It may take up to two weeks to arrive though.

Cheers,
Corey

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Re: Apple 1 keyboard Micro Switch 1974

by the way, my guess is that 28 pin IC is a ROM or PROM. They were often used as state machines or decoders back in the day.

regards,
Mike W.

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Re: Apple 1 keyboard Micro Switch 1974

I took a closer look at the keyboard this evening after work.

The AMI SW20276K is wired with:

 1-13: keyboard matrix
   14: N/C
15-21: bit 0 through bit 6
   22: "shift"-able character pressed
   23: "control"-able character pressed
   24: key pressed
   25: N/C
   26: +5v
   27: ground
   28: -12v

Pin 13 is connected to keys N, M, K, L, O, and P. These are all characters that can be altered
with both a shift key and control key at the same time.

Pin 24 is active as long as a key is pressed.

The data bits and and pins 22 and 23 are latched by the chip, which means that the Apple 1
can capture the data when the strobe returns high.

The switches themselves are hall effect switches, and most of them pull down the line when
pressed. The shift and control keys both pull their respective pins up. The two tape left/right
keys simply output a brief low pulse. Each key has two output pins, most of these are connected
to the matrix inputs on the SW20276K. The shift, control and "special function" keys are either
connected to the edge connector or circuit that handles the shift and control functions.

On the keyboard that I have, there is also a 7400, MC846P, and 7486. These handle the alteration
of the results when the shift and control keys are pressed, as well as ensure that a strobe is
activated when a valid key combination is down. The 20276 outputs an inverted bit 4 and 6, which
are normally inverted by the 7486 to form the normal ASCII character. Pressing a control or
shift key will adjust the results to form the shift/control version of the keys pressed.

The remaining two gates from the 7486 square up the brief pulses from the tape left/right keys to
emit a 228usec low pulse.