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Help identify a keyboard (DB-9 male)

H

Half-Saint

Experienced Member
Joined
Apr 21, 2004
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322
Location
Ljubljana, Slovenia
Just picked up a curious keyboard today labeled Solid State Logic (Rotec International Ltd. Made in UK). It's not as big (lenght-wise) as a standard 102 key keyboard but the layout is pretty much standard PC. It's a clicky keyboard and uses blue Cherry switches. The PCB is dated 1992. On the bottom there's a hole where a PC AT switch is supposed to be but it's obvious that the PCB has no connection points for the switch. There a Philips pcb80c31bh chip in there but that doesn't help much. There's also an eprom onboard but I have no idea what's inside :)

What's curious about the keyboard is that it uses a DB9 connector. What I want to know is how can I find out if it can be connected to a standard PC?

Thanks
SainT
 
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Half-Saint said:
What's curious about the keyboard is that it uses a DB9 connector. What I want to know is how can I find out if it can be connected to a standard PC?
Click to expand...

Probably. I've got a keyboard from Advanced Input Devices like that (it's switchable XT-AT) but fitted with a DE-9P instead of the usual DIN connector. This was used as part of a lab scale from GSE. Often, where there was an application for an embedded PC a different connector was used.

Fortuantely, it's easy to figure out what's what if you want to put a DIN connector on. The +5 and ground wires can easily be deduced by their connection to the 8031 microcontroller supply lines. That leaves you with clock and data--and you've got a 50 percent chance of getting those right--and no harm if you get them wrong.
 
Chuck(G) said:
Fortuantely, it's easy to figure out what's what if you want to put a DIN connector on. The +5 and ground wires can easily be deduced by their connection to the 8031 microcontroller supply lines. That leaves you with clock and data--and you've got a 50 percent chance of getting those right--and no harm if you get them wrong.
Click to expand...

I'd like to avoid removing the PCB. Hopefully, black is GND and red is +5 :) The other two then must be clock and data. What happened to reset?

Cheers
 
Half-Saint said:
I'd like to avoid removing the PCB. Hopefully, black is GND and red is +5 :) The other two then must be clock and data. What happened to reset?
Click to expand...

You're fortunate. On my keyboard cables the conductors are green, black, brown and white.

Very few keyboards actually connect reset to anything and almost no PCs rely on the keyboard reset line. PC XT keyboards rely on the host holding clock low for an extended period to initiate reset. PC-AT keyboards use a hex FF command from the host to initiate reset.

It's ever been thus. Take a look at page 2-18 in the PC Tech ref that shows the keyboard connector pinouts. Note that pin 3 says "-Keyboard reset (not used by keyboard)".

The reset line falls under the heading of "good idea, but complete superfluous". Many PS/2 keyboard mini-DIN plugs have only 4 pins.
 
Well just took a quick look this morning and there are actually 6 wires going out from the PCB. As you say, only 4 are probably used.. will have to trace the PCB to see what's what. One wire is indeed red and one black, one being the first and one the last in the row.
 




Sorry the photos are not the greatest and I couldn't take a much better photo of the pcb as the flat cables are attached directly to the PCB and the same goes for the ground wire.

Cheers
 
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Nice keyboard! It looks like it may have been used for some sort of industrial control application. The compact form may have been to fit into a standard EIA rack tray.

As far as identifying leads, observe that the +5 will be connected to pin 40 and Gnd will be pin 20 on the PCB80C31BH IC. From what I can see, these would be the 2nd and 3rd leads after the black wire (which must be connected to the cable shield) counting from the wire closest to the LEDs.

As for the rest, I can't make out very clearly on the top-side photo where the cable attaches, so it's difficult to say.
 
Thanks for the input :) I need to get my hands on a soldering iron one of these days..

Also picked up a dusty old NeXT station keyboard this morning for 2€ at the local flea market. Hope it works :)
 
I'd have to agree that it looks like an industrial keyboard, but judging by the condition, either it was cleaned up very nicely or was never used in that situation.

Oooh nice find on the NeXT keyboard.
 
Chuck(G) said:
As far as identifying leads, observe that the +5 will be connected to pin 40 and Gnd will be pin 20 on the PCB80C31BH IC. From what I can see, these would be the 2nd and 3rd leads after the black wire (which must be connected to the cable shield) counting from the wire closest to the LEDs.
Click to expand...

Hey! I finally bought myself a soldering iron and decided to finally give this a go. Anyway, what I figured out so far is this:
Black - GND
White - Vcc
Yellow..Red - connected to SN751798p chip outputs (pins 5-8 or A,B,Z,X)
I have no idea how to figure out the outputs of this chip...

Any help appreciated :)

Cheers,
SainT
 
Are you sure that's not a SN75179BP chip? If so, that's an RS-422 differential transceiver.

It sounds as if this might be a plain old async serial keyboard, rather than a PC (clock+data lines) type. The 4 remaining wires are probably the differential input and output to the keyboard. Kind of neat, in its way.
 
Chuck(G) said:
Are you sure that's not a SN75179BP chip? If so, that's an RS-422 differential transceiver.

It sounds as if this might be a plain old async serial keyboard, rather than a PC (clock+data lines) type. The 4 remaining wires are probably the differential input and output to the keyboard. Kind of neat, in its way.
Click to expand...

Yep, you're right, it's SN75179BP. I checked the datasheet I got the data from in the first place. So, can this thing be hooked up to a PC or not?
 
Half-Saint said:
Yep, you're right, it's SN75179BP. I checked the datasheet I got the data from in the first place. So, can this thing be hooked up to a PC or not?
Click to expand...

Not through the keyboard port. Perhaps through a serial port.

At least that's my best guess. I wonder if this thing belonged to a terminal (not a PC) in its previous life... :?
 
Chuck(G) said:
Not through the keyboard port. Perhaps through a serial port.

At least that's my best guess. I wonder if this thing belonged to a terminal (not a PC) in its previous life... :?
Click to expand...

Funny thing is, the layout is almost exactly the same as a regular PC down to the Alt Gr key! I don't see any terminal specific keys either... maybe I should connect it to a serial port and run a terminal program, see what that does... if it's a normal serial port, it should give me some output. What do you think?

Cheers
 
Half-Saint said:
Funny thing is, the layout is almost exactly the same as a regular PC down to the Alt Gr key! I don't see any terminal specific keys either... maybe I should connect it to a serial port and run a terminal program, see what that does... if it's a normal serial port, it should give me some output. What do you think?
Click to expand...

Maybe, but I suspect that this one doesn't have the +/-12v swing needed for RS232C operation. RS-422 is a low-voltage differential signaling method.

The 8-pin transceiver chip that this uses has one channel for each direction; a PC has at least two output lines (one for clock and one for data)

Google "RS422 Keyboard" and you'll see that these are used extensively in commercial applications, such as POS terminals and video editing.
 
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