lot of ways to skin this cat. 1 look at any keyboard matrix schematic (like the one in the 100 itself). Keyboard matrixes add diodes to the switches to get a lot more switches than wires.
2 could use an 8 to 3 encoder to turn up to 8 individual switches into 3 bits of output. Read those 3 bits with the 3 available rx cts dsr. 74HC148 is a perfectly small cheap and chronistic part widely used at the time so not cheating. There are a few other similar related chips with tweaks to the behavior like active high vs active low etc. bcr port can read real fast, faster than the serial port. I bet there is a similar parallel to serial register chip that could read 8 pins and stream out pulses on a single pin. I don't know how you'd sync up with it though. You'd need a clock in the joystick to continually trigger the multiplexer and then idk how you detect the begin and end of a dump from the 100. I guess have the clock only trigger the chip every other pulse and detect the long blank. bkw On Tue, Sep 23, 2025, 9:42 PM Scott McDonnell <[email protected]> wrote: > I am back to thinking about a joystick for the Model 100. I have a > specific reason in mind and even a specific joystick. > > My intent is to target the Atari/Commodore 64 digital joystick interface > mainly because my inspiration is the Suncom Icontroller which mounts to > the side of the machine. > > This interface is a series of 5 discrete switches to control direction > and a fire button. Very basic. > > While the parallel port would have been ideal for something like this, > it is not bidirectional and offers only two inputs. > > The serial port provides 3 inputs; still not enough > > While some multiplexing strategies might allow this to work, both of > those ports are also often used for other important purposes. > > So I started thinking about the barcode port. It only has one input, but > the joystick could be encoded into a serial stream. Maybe even using the > original barcode drivers. I don't know the specifics of the BCR > implementation here, but often they are just keyboard wedges. > > Any thoughts on this or a better solution? > > >
