CoCo to IBM PC XT (AT?) Bob Puppo Keyboard Adaptor

[IBM Portable PC]

I know we can now buy PS2 adaptors, however it would be neat to be able to use this instead. Something you can actually easily build and modify etc.

A Bob Puppo is on eBay now: https://www.ebay.com.au/itm/154448488371

Does anyone have a schematic and firmware already?

 

[IBM Portable PC]

Okay, I’ve found the schematic here: World of 68' Micros, The - Vol. 1 Number 2 (1993-09-15)(FARNA Systems)(US)

I’ve also purchased an actual adaptor and will dump the ROM and upload it to this thread in the near future.

PS2 adaptors are great, however the Puppo adapter was the way we did this in the 80’s, if we could afford the then $100 asking price!

 

[Eudimorphodon]

I know we can now buy PS2 adaptors, however it would be neat to be able to use this instead. Something you can actually easily build and modify etc.

FWIW, if an open-source solution is what you're after I imagine it'd be pretty simple to modify the C-Key to use on a CoCo, they're both simple matrix keyboards. Should just be as simple as re-defining the output matrix positions.

(If you prefer PIC MCUs to AVRs another option would be the PS/2 keyboard circuitry for this TRS-80 clone. My vague recollection is that the Model I and CoCo's matrices are almost identical so if the source is included that might be even less work. Both designs are little more than MCU and a matrix switch.)

 

[IBM Portable PC]

Here is why I prefer discrete components. The Puppo adaptor uses http://radio-hobby.org/uploads/datasheet/38/mc14/mc142100.pdf crosspoint switches, controlled by the MC6802, to simulate key presses. This simplicity is both elegant and very appealing to me, much more so than a tiny single chip with all workings invisible to the naked eye.

 

[Eudimorphodon]

Here is why I prefer discrete components. The Puppo adaptor uses http://radio-hobby.org/uploads/datasheet/38/mc14/mc142100.pdf crosspoint switches, controlled by the MC6802, to simulate key presses. This simplicity is both elegant and very appealing to me, much more so than a tiny single chip with all workings invisible to the naked eye.

The C-Key does use a crosspoint switch, an MT8812. Conceptually it's exactly the same thing except the MCU has a built-in ROM (so no need for an external eprom) and you only need one 8812 instead of four of the 142100s. Both the MCU and the crosspoint are available in through-hole versions so it's equally accessible to home builds.

Now it is true that the C-key includes support for stuff that's extraneous on the Coco, like the "use it in reverse" mode, digital joystick ports, etc. (And an 8x12 matrix switch is also technically overkill.) But if you wanted to chop it down to use an MT8808 8x8 switch and eliminate those extra bits that should be totally doable.

(* That other one I mentioned uses a PLD to emulate a crosspoint switch but is, again, conceptually essentially the same.)