I have been busy 🙂
Now I have all the different computers working, it was time to get interfaces for them so they can fulfil their prime purpose. To wit: Video Games!
Texas Instruments TI 99/4A
I have a PCB design ready to go for this, but in the meantime, I decided to make a temporary adapter to allow me to use “Atari” type joysticks on the TI. This is a quite simple project, consisting of a few diodes, so I grabbed some experimenter’s board and bodged together an adapter. It works quite well. I played Donkey Kong on the TI for quite a bit.
Dick Smith Wizzard / CreatiVision
The next batch of PCBs arrived, and I slowly and carefully assembled up another controller. There was a bit where I thought I’d made a terrible mistake, but no. It’s perfectly fine.
Building a controller.
Building one is pretty easy, as long as you’re comfortable working with SMD components. I tend to flow some solder on one pad, use tweezers to hold the component in place, then flow the pad with solder on it until the component is flush. I then flow some fresh solder onto the other pad. Use flux liberally and a suitable soldering tip and you’ll be fine. (I use a narrow “needle” tip just for this work.)
Initially you’ll need to cut the various PCBs into sub boards. Sharp scissors work well for that. The PCBs are really thin so it “just works”. Clean up the edges with a small file if needed.
Now you will need to prep the “donor” controller shell. Remove the membrane completely and desolder the rainbow cord from the small PCB it’s attached to. Remove the rubber contacts from the trigger buttons. Clean everything as needed. You’ll need to save the clear thick disk that sits on the membrane beneath the joystick, the spring, the thin plastic bit from on top of the joystick and below the shell, the joystick piece itself and the foam ring.
Now collect the keyboard PCB and add the various SMD switches and diodes. Note the polarity of the diodes. You’ll also need to SMD solder the two switches for the trigger buttons on the small Trigger sub boards.
This is the point where I’d solder all the bits and pieces to the central “joystick” part. For this one I, uh, kinda did it out of order because I was not sure some of the stuff I was working on would, y’know, work.
Let’s pretend I did it in a sane way…
Next solder the two wires to each of the trigger sub boards. I’ve been deliberately soldering these to the “surface” of the PCB so the board sits flatter. Connect the other end to the central PCB.
Next tack the upper disk part of the central joystick to a small wire and connect it to the base. Again, I surface tack to keep the PCBs flat.
Next comes the “tricky” part. We’re going to interconnect the keyboard section and the central joystick section. This is also the part I’m most proud of, because despite being tricky, it’s quite manageable and easy to do. Just take your time.
Take some solid core copper wire. If it has insulation, strip off the insulation as you’ll need to solder to it in a non standard way.
Place the central PCB on a heatproof surface, as flat as you can get it. Insert the copper wire through the first of the soldering points and apply solder to the top surface of the wire. Once firmly in place, cut the wire about 12mm from the PCB. This will ensure the PCB is flat on the bottom.
Repeat for the next 9 holes.
Time to connect the rainbow cord to the core PCB. Now the order the pins connect to the PCB is not a straight mapping, and you’ll need to tone out which wire connects to which pin on the cable. the pins are counted left to right on the CreatiVision itself. Pin 1 on the PCB is marked.
The connection is as follows:
|Connector||Pin on the PCB|
Now, this is the time to get the keyboard board and the base joystick board aligned.
Drop the base into the controller frame and make sure it’s positioned correctly. I used Blu Tack to help keep it aligned. Next slide the keyboard board over the copper wires coming from the joystick board. Now you can align the keyboard board on the connecting pins and get everything aligned properly. Once both the joystick board and the keyboard are in alignment properly on the controller frame, solder the pins into place on the keyboard board. Cut off any excess copper wire and move onto the next step.
The final step is to build and align the trigger buttons.
This is about the only bit I’m not entirely happy with.
First off, you’ll need to mount in a small “pusher” where the contacts on the rubber dome used to be. I used a piece of skewer cut to size.
Now you will need to fit the PCB for the triggers and make sure the pusher presses the button correctly. On one of my joysticks it worked first go. On the other, I ended up having to sand down one of the triggers a little, trim the PCB and hold it in place with thin double sided tape. YMMV. I have no idea why one worked fine and the other was a mess of filing and fiddling.
Now for final assembly.
Place the thick clear ring you salvaged between the joystick board and the disk board. They should be nearly touching but not quite. Place the foam ring on top of the ring board. Place spring on top of the ring board around the foam ring. Assemble the joystick and clear sheet into the upper shell, and holding the joystick piece to keep everything in place, clip it to the bottom shell.
Make sure no wires are pinched!
Now you can screw the two halves back together again. Pat yourself on the back. It’s built.
TRS-80 Colour Computer 2
The Colour Computer uses a proper analog joystick system, measuring a voltage differential between ground and 5V across a pair of potentiometers. This means, like the BBC Micro, it’s a lot less fussy about what sort of potentiometer it uses.
I was hoping it was REALLY not fussed, and that I could use it with cheapo “all in one” joystick assemblies I could get locally.
Taking a punt, I purchased one, as well as all the connectors and a suitable shell for the joystick. I made up a simple test rig on some protoboard and the joystick seemed to work OK.
I cut some M3 nylon spacer to size, to mount the joystick PCB so that the top of the PCB was in alignment with the top of the shell. I used a rotary tool to cut out a hole so the button wouldn’t be impinged by the unused battery compartment.
I used a step drill bit and a file to make a suitable hole in the top for the joystick.
After that, it was a simple matter of wiring the appropriate pin to the appropriate pin. 5V on the CoCo connector to 5V on the joystick and so on. The only “tricky” thing was working out the fire button connects between the appropriate pin and the ground wire.
(It was at this point I realised I’d mounted the joystick upside down. This meant I had to make the hole for the joystick wider,as the joystick wasn’t symmetric to the mounting posts. Gah!)
I made up some strain relief for the joystick cable. On the inside, this consisted of a cable tie. Externally I used some glue lined heatshrink.
Now I could properly assemble it. Some screws in the bottom and it was ready to use. Time to play some Donkey King! 😀
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