Substitute keyboard for Magnavox VideoWriter?

[Bill-kun]

I have two Magnavox VideoWriters. These are dedicated word processors from circa 1986. Neither came with their keyboard. The keyboard port is a 4P4C (shape and size for a U.S. telephone receiver cord). Is it possible for me to just homebrew a wire adaptor for a standard 5-pin DIN or PS2 keyboard? If so, what is the wire mapping? Or if I had a terminal keyboard with a 4P4C connector, would that work?

More of someone else's pictures here.

 

[westveld]

Looks like a neat machine!

See: https://hackaday.io/project/25664-anatomy-of-a-philips-videowriter/log/172155-the-keyboard

Looks like it's a sends it's keystroke buffer serially when the CPU asks it to.

I don't other keyboard protocols enough to know if any other common type would work.

 

[Bill-kun]

See: https://hackaday.io/project/25664-anatomy-of-a-philips-videowriter/log/172155-the-keyboard

Inside the keyboard we find a NEC D8049HC microcontroller. It has 2KB of program ROM and 128 bytes of RAM. The microcontroller scans the keyboard switches and handles the communication with the VideoWriter.

I have no idea if ordinary DIN5 or PS2 keyboards have microprocessors in them (I never until now even thought that would be a thing), or if they would do the same processing. If not the same processing, then any keyboard other than the proprietary ones would not work at all--unless I built my own substitute microprocessor.

The key codes that are sent by the keyboard are normal ASCII character codes for the regular keys. For the 'special' keys such as backspace, return and tab these are not the regular ASCII codes, same as for the function keys.

So if I homebrewed an adaptor from DIN5 or PS2 that was just a physical remapping, only the "regular" keys would register correctly; backspace, return, tab, etc., would also all need to have their signals translated by the homebrew microprocessor as well.

I'm not saying building this homebrew microprocessor would be impossible for me, but it is so far beyond my present skill in electronics that it would take about a year for me to get that skilled. Again, not saying that would never happen, or that I wouldn't gain cool knowledge, but that is a long hill to climb for such a seemingly small result.

Until and unless I do--rats. It looks like the simplest thing to do is just seek out a proprietary keyboard. And since that is doubtful without the main unit itself, the best bet is to just seek out a complete unit that includes a keyboard, essentially acting as if I didn't own these two VideoWriters in the first place.

 

[Chuck(G)]

Awhile back, I posted a bit on a AID (Advanced Input Devices) keyboard that was basically a PC-XT style keyboard, with a DE-9 connector. I finally puzzled out what the thing was, and it turns out that it sent plain old ASCII in 8N1 serial format.

So yes, you can adapt a keyboard with a little programming on a cheap MCU to work with your box. It looks as if the keyboard vampires have consumed the existing ones--though I don't know why.