[vcf-midatlantic] much ado about chording keyboards

Jonathan Gevaryahu jgevaryahu at gmail.com
Fri Nov 29 04:40:06 EST 2019

On 10/1/2019 10:24 PM, Jonathan Gevaryahu wrote:
> On 9/29/2019 1:14 PM, Eric Rangell via vcf-midatlantic wrote:
>> Thanks Jeff.
>> To give context to this discussion, I built a chording keyboard for 
>> my Replica 1 and Apple 2+ by interfacing an Arduino to the keyboard 
>> socket and using 5 arcade momentary switches from Micro Center.  I 
>> coded it so that my fingers chord a hex nibble and the thumb strobes 
>> it into the Arduino, and the LED shows whether you are chording the 
>> high nibble or low nibble.  It is possible to recode it for other 
>> chording mechanisms and add switches to choose a mode.
>> Eric
> Eric, that reminds me: did you ever get a chance to probe out all the 
> outputs of the GI "AY-5-3600-931-B6" (second sourced as SMC 
> "331-0931-B KR3600-070" ) from the early apple2/plus keyboard, for 
> every possible keyboard input, shift+input, ctrl+input and 
> shift+ctrl+input combination?
> I.e. what data in B1-B10 (pins 14 down to 5) is returned, if any, for 
> every possible unique X-bus output (on pins 40 down to 32) and for 
> each unique X-bus output, every possible Y-bus input (on pins 26 down 
> to 17); this whole process gets repeated 4 times, with neither shift 
> (pin 29) nor control (pin 28) asserted, shift asserted, control 
> asserted, and both shift+control asserted.
> See 
> http://www.bitsavers.org/components/gi/_dataBooks/1980_GI_Microelectronics_Data_Catalog.pdf 
> page 3-23 (pdf page 134)
> I'm trying to improve the accuracy of the apple2 keyboard emulation in 
> As far as I'm aware, the 331-0931-B uses the very last mask option on 
> the list, where pin 4 is AKO and pin 5 is B10.
> I'm guessing these tests will require an arduino mega to read the 9 
> X-bus outputs in a fast loop and sequentially supply a 10-bit y-bus 
> input when the x-bus reaches the correct 'count' being probed, and 
> immediately after that either poll the AKO pin, and if it goes active, 
> immediately read the 10-bit B bus, or just read the 10-bit bus and 
> assume it detected a key-down.
As it turns out, Sean Riddle decapped one of these, so it should be 
possible to create an exact replica on a microcontroller, or out of an 

and it also turns out, about a week ago, someone dumped the eprom from a 
clone apple2/2+ keyboard which DOES use an ay-5-3600-pro plus an eprom, 
see https://www.applefritter.com/content/clone-keyboard-eprom-data-intact

So between those two things, it should be very possible to make a 
replacement part/board for burned out SMC KR3600-070 or AY-5-3600-070 or 
331-0931-B parts.

Jonathan Gevaryahu
jgevaryahu at gmail.com
jgevaryahu at hotmail.com

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