Interfacing a PS/2 Keyboard for homebrew CPU

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bitbyteword3

New Member

• May 29, 2011

• #1

I'm designing an 8-bit CMOS CPU. I would like to interface a PS/2 keyboard as input for the computer. I would like to let it have 8-bit output (the scancode). What is a parity bit?

 

Brevor

Member

• May 29, 2011

• #2

https://en.wikipedia.org/wiki/Parity_bit

Click to expand...

...........

 

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bitbyteword3

New Member

• May 30, 2011

• #3

.... LOL what?

 

Brevor

Member

• May 30, 2011

• #4

It's a link, everything you need to know about parity bit.

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• May 30, 2011

• #5

Is it just me?, or do others think it's strange that someone 'designing a CPU' doesn't know what a parity bit is.

It's like designing a car and not knowing what a wheel is.

 

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bitbyteword3

New Member

• May 31, 2011

• #6

*an application for the parity bit. Sorry, I don't know how I missed that. Any way to interface the keyboard?

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• May 31, 2011

• #7

bitbyteword3 said:

*an application for the parity bit. Sorry, I don't know how I missed that. Any way to interface the keyboard?

Click to expand...

Of course, it's a standard device - you need a bi-directional syncronous serial port, either in hardware or software.

https://en.wikipedia.org/wiki/PS/2_connector

 

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bitbyteword3

New Member

• May 31, 2011

• #8

I'm thinking of using the 4034 since I want a parallel output. Is this good? How will I get the scancode?

 

ericgibbs

Well-Known Member

Most Helpful Member

• May 31, 2011

• #9

bitbyteword3 said:

I'm thinking of using the 4034 since I want a parallel output. Is this good? How will I get the scancode?

Click to expand...

hi,
Do you have Visual Basic 5 or 6 on your PC.?
I have a simple ATKbd simulator source code, [ about 5 years old] written in VB, which you could use to work on the key codes.

You realise you need to send: key down code, key code, key up code for each key, also all the Caps/Alt keys etc.??

EDIT:
Note the HEX key codes on the key tops of this image.

 

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Last edited: May 31, 2011

ericgibbs

Well-Known Member

Most Helpful Member

• May 31, 2011

• #10

hi,
I have retraced the source of my original data, look thru these links.
https://www.google.co.uk/search?source=ig&hl=en&rlz=&q=microchip%2Fprojects%2Fkeyboard&btnG=Google+Search&aq=f&aqi=&aql=&oq=

This is the one I used.
https://electronic-engineering.ch/microchip/projects/keyboard/v1xx/keyboard_v1xx.html

 

Last edited: May 31, 2011

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bitbyteword3

New Member

• Jun 2, 2011

• #11

I must be more specific - PS/2 Keyboard decoder with parallel output of all 11 bits. No MCUs.

 

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bitbyteword3

New Member

• Jun 2, 2011

• #12

I must be more specific - PS/2 Keyboard decoder with parallel output of all 11 bits. No MCUs. Any schematic for that?

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• Jun 3, 2011

• #13

You simply connect the PS2 keyboard directly to two I/O ports on your CPU, and do it in software.