PS/2 keyboard adapter for VIC20 and C64

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levoman
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Re: PS/2 keyboard adapter for VIC20 and C64

Post by levoman »

Tested and verified fully working with 5 pin din or PS/2 connector . PCB is now on PCBWay ready for ordering .

https://www.pcbway.com/project/sharepro ... board.html

Works with C64 and VIC20.


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eslapion
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Re: PS/2 keyboard adapter for VIC20 and C64

Post by eslapion »

Very nice design but I am scratching my head a bit here.

The only available package for currently produced MT8808 is 28 pins PLCC but I only see DIP footprints on your PCB design. One can always get old units on eBay but there are pretty much all from China with a pretty good chance of getting fake/defective ICs.

Also, if you consider the possibility of making a C128 keyboard adapter then the MT8816 is presently in stock at Mouser in DIP only. None of any kind at Digikey.

Unless of course there is something important I am missing here.
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Re: PS/2 keyboard adapter for VIC20 and C64

Post by levoman »

Indeed , china is where i got mine from , and not fake either!

https://www.aliexpress.com/item/4000251 ... 4c4dXsAmDp
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Re: PS/2 keyboard adapter for VIC20 and C64

Post by levoman »

If the plcc version is used it would make it harder for beginners to solder.
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Re: PS/2 keyboard adapter for VIC20 and C64

Post by banman »

Hi levoman and eslapion,




I got mine from here....



AU $2.41 3%OFF | 1pcs/lot MT8808AE MT8808 DIP-28
https://a.aliexpress.com/_mLb9Fp0

AliExpress has a dispute resolution center for items that don't work. I have used this process a few times successfully. I won't consider buying from a vendor unless I have the ability to get a refund/ return on faulty products.



I found it a very easy build for a hobbyist with thru hole construction.

It is true many parts that come from China have a poor credibility rating. I have on a number of occasions received items that have been rebadged. It seems like the seller's feel a need to be selling new parts instead of advertising them in their original condition.
I know most of the vendors know little about where the parts come from and if they work or not. Maybe, that's why they are made to look 'like new'. In an attempt to confuse the buy.





How hard would it be to create a crosspoint switch using something else say like a gal chip?


It is getting harder and more expensive to get original keyboards and parts for Commodore machines. I wonder how common it is to get keyboard spares for other 8 bit systems.....
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Re: PS/2 keyboard adapter for VIC20 and C64

Post by eslapion »

levoman wrote: Thu Dec 02, 2021 11:17 am If the plcc version is used it would make it harder for beginners to solder.
I don't know if I'm a beginner but I find it incredibly easy to solder a PLCC but incredibly difficult to program the micro-controller you have chosen.

I think its more a matter of approaching the project with a different set of experience, knowledge and tools. You can't assume everyone has the same as yours.
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Re: PS/2 keyboard adapter for VIC20 and C64

Post by levoman »

I also , in all honesty , can't get all the equipment people might have and show every variation on it . The project has to be limited somewhere .

If enough people want a different version i will track a new pcb for it. Please leave a request on the forum if you would like something different.
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Re: PS/2 keyboard adapter for VIC20 and C64

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levoman wrote: Fri Jan 21, 2022 4:01 pm I also , in all honesty , can't get all the equipment people might have and show every variation on it . The project has to be limited somewhere .

If enough people want a different version i will track a new pcb for it. Please leave a request on the forum if you would like something different.
Way back in the past (around 2006), I created the Ultimate Expander cart for the VIC-20. At the time, I didn't know if people were going to get the required 32k SRAM chip in DIP format or SOIC so I had the PCB designer create a SOIC footprint INSIDE the DIP footprint space.

I do not know by heart the space required for the DIP vs the PLCC version of the MT8808 but do you think it's possible to pull off a similar trick ? To have the PLCC footprint fit inside the DIP footprint so you can use whatever package you can obtain ?

AFAIK the DIP package is discontinued so you can only get it on eBay, Ali(whatever) and most of them can be Chinese fakes.

Presently available packages for this chip on both Mouser and Digikey are PLCC only.
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Re: PS/2 keyboard adapter for VIC20 and C64

Post by levoman »

The project is now on my website

https://www.levosretrocomputerprojects. ... rd-adapter

I have used this trick with the keyboard sockets , but i do not think it will work with the IC's especially with the 20 pin connector in the middle!

If enough people want one then i will do a full SMD version ( apart from the c64 and keyboard connector ) .

Please leave a note on the forum if you would be interested.
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Re: PS/2 keyboard adapter for VIC20 and C64

Post by banman »

Hi Levoman and eslapion,


That's a very good write up of the keyboard adapter levoman.


That's an interesting idea regarding the PCB footprint eslapion.


I was wondering if it were possible to make plcc to 28 pin adapter PCB board. This way the plcc adapter board could be plugged into the current PS 2 keyboard adapter PCB board 28 pin dip socket?

The plcc to 28 pin adapter PCB could just be a simple soldered directly to the PCB affair or a more elaborate plcc plastic socket version could be configured.

It could be a good way for hobbyists to stretch their direct plcc ic package to PCB board soldering techniques with out the risk of messing up the original PS 2 keyboard adapter PCB board.

I would be willing to give it a try.


By the way I have been further testing this project and I can confirm that it works with numerous PS 2 keyboards and USB keyboards with a PS 2 to USB gender changer and a wireless keyboard no problems. It seems to work fine using an Atmega8 AVR.

It will work on a 4mHz external crystal oscillator though some USB keyboards need 8mHz external crystal to fully work. Not too sure why this is.

With a wiring harness modification it too works on a C16.

I suspect that AT style, PS 2 style and USB style keyboards are all serial in nature. It is the plug connector that is different.
Last edited by banman on Sat Jan 22, 2022 11:18 am, edited 2 times in total.
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