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View Full Version : An S-100 Board to convert IBM PC keyboard data to parallel ASCII



monahan_z
January 2nd, 2010, 11:46 PM
Many S-100 users have/had some kind of ASCII style parallel port keyboard attached to their system. The interface was just a simple 8 bit parallel input port with a second port single strobe bit. Most of these keyboards came from old mini computer systems or simple CRT terminals. Today they are now quite difficult to find. If there are any parallel port keyboards on eBAY etc. from Atari systems and the like, they are usually not in ASCII format but instead deliver key press data in X,Y coordinates etc. Today almost all PC systems interface the user via an IBM PC (AT) type keyboard. This is in fact may be the single most lasting effect the IBM PC has had on the PC business in the past 30 years.

However the IBM keyboard does not return data to the computer via a parallel port. Instead it does so in a more sophisticated manner via a bidirectional serial communication mode. Each key returns its own (single or multiple 8 bit code) which is different on the key down and up strokes. It also depends on the status of the Ctrl, Num, Alt and other keys.
I wanted a way to get simple ASCII code from the keyboard.
Over the years many have tackled this challenge in various ways to hammer an ASCII code out of these keyboards. Some use elegant single chip CPU/IO chips, others various TTL logic chips. I decide to tackle the problem head on by using the age old Z80 CPU, RAM/ROM and a few Zilog PIO's. (They cost next to nothing these days). This not only allows one to completely control the data sent from each and every key combination simply (lookup tables), but the keys can be dynamic, function keys can return varying strings depending on the application etc. I chose the Z80 because almost everybody in the S-100 bus world knows the opcodes and can easily program a simple common 2716 EPROM or the like, for their own specific applications/desires. They can test and modify my code under CPM and in general play around with the system.

I put together an S-100 prototype board that is described here:-
http://s100computers.com/My%20System%20Pages/IBM%20Keyboard/IBM%20Keyboard.htm

It has been working daily now for 6 months.

With Andrew Lynch (see http://n8vem-sbc.pbworks.com/) we have designed and are about to fabricate a few commercial style S-100 boards. Fun stuff, but not for everybody!
BTW, we are also doing another run of the IDE S-100 board.

Erik
January 3rd, 2010, 07:38 AM
That sounds absolutely awesome, guys!

I'd never even thought of it as an option! :D

NobodyIsHere
February 9th, 2010, 03:55 AM
Hi! The S100Computers.com & N8VEM S-100 keyboard PCBs have arrived and John and I are in the build and test phase now. The good news is the board is checking out fine and works. There are a few minor clean up issues and we are thinking about a clean up respin of the PCB.

It is a neat project and a fun board to watch it working. John has a neat page up on S100computers.com demonstrating it. I think there is an update in the works too. This board will be very useful to S-100 hobbyists with parallel input ports (Northstar Horizon, etc) and/or video boards with parallel ASCII keyboard interfaces (VDB 8024, VG FlashWriter, etc)

Since it uses a readily available PS/2 keyboard it can make restoring a vintage S-100 system a lot easier by avoiding the issues of obtaining and interfacing a parallel ASCII keyboard to your system.

Thanks and have a nice day!

Andrew Lynch

NobodyIsHere
October 15th, 2010, 04:10 AM
Hi! Good news! All of the S-100 parallel ASCII keyboard converter boards have gone to their builders. We've gotten a lot of feedback on the board and several builders are on the waiting list for another PCB manufacturing run. I've updated the design to address all the issues of the initial version and made some simplifications.

My plan is to get some more boards as soon as the updated design finishes trace route optimization. Most of the boards are already accounted for but if you would like to get one of these please contact me and I'll add you to the list. I can easily make the order larger but if you if you miss this PCB order it will likely be months before it comes around again as it is a rather specialty item.

The boards work well and are a really nice addition to a restored/vintage S-100 system. They are also just a lot of fun to use since they have lots of Blinkenlights and make using vintage S-100 systems very interactive. John has a nice web page up on S100computers.com describing the board with build instructions, demonstration video, etc.

http://s100computers.com/My%20System%20Pages/IBM%20Keyboard/IBM%20Keyboard.htm

Please let me know if you are interested. Thanks and have a nice day!

Andrew Lynch

NobodyIsHere
November 4th, 2010, 03:17 AM
Hi! The next batch of the S-100 Parallel ASCII keyboard boards should be here in the next few days. If you are considering restoring a vintage S-100 system, especially one with a video board or one that requires parallel ASCII keyboard input this board will be very useful to you. These boards include all the feedback and corrections from the first run so they should be much cleaner to build and use. Please contact me if interested.

Thanks and have a nice day!

Andrew Lynch

NobodyIsHere
November 6th, 2010, 10:56 AM
Hi! The S-100 parallel ASCII keyboard PCBs have arrived and are going out to their builders. There are some extras so if you would like one please contact me. These boards have gone through respin to correct all the issues with previous versions and improved trace routing. Please see S100computers.com website link above for more information on the board.

They are $20 each plus $3 shipping in the US and $6 elsewhere. Since these are rather specialty boards it will probably be several months at least before there is another order of them.

Thanks and have a nice day!

Andrew Lynch

NobodyIsHere
February 28th, 2011, 05:10 AM
Hi! I still have a small number of these PCBs left so if anyone would like some please let me know. This is a nice looking board in any vintage S-100 system and blends in well. The displays are very useful and interesting to watch. The commonly available PS/2 keyboard is an inexpensive and reliable way to communicate with your system.

http://s100computers.com/My%20System%20Pages/IBM%20Keyboard/IBM%20Keyboard.htm

Thanks and have a nice day!

Andrew Lynch