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PROTOVISION 4 Player Interface

4 Player Interface
This section is under construction.

4 Player Interface building and programming instructions
Commodore 4 PlayersMulti-player gaming can be great communal fun on any computer. Unfortunately, the C64 normally has got only two ports for joysticks. So what to do about that? Protovision developed a simple interface, plugged into the userport of your C64, which provides two more ports for joysticks. It was a huge success, and that is reason enough for us to provide you the instructions on how to build it, and if you are a programmer, you also get the documentation on how to code for it, to use it in your own productions. You can of course also buy one instead of building it on your own.

Building your own 4 Player Interface
Look at these sketches, they will help show you how to build your own 4 player interface!

Userport-Connector
Joystick-Connectors

Here are the parts and tools you need to build a 4 Player Interface on your own. Please note: The part list applies for the form of the interface when it was introduced - of course you can use other forms, like long cables for each joystick port which lead to a parallel-cable-like userport connector in which you place the IC.

Parts Tools
  • little case
  • IC 74LS257
  • IC socket with 16 pins
  • two 9pins sub-D male connector
  • circuit board (for example raster matrix board for 4 16pins IC)
  • Userport connector
  • Userport connector cover
  • screws and nuts (i.e. RS232 set)
  • 100 cm 10-lined flat cable
  • tweesers
  • soldering iron (25 Watt)
  • knife
  • screwdriver
  • drilling machine
  • driller (2.5 mm)
  • saw
  • file
  • insulation tape
  • vice (the helping 3rd hand)


First create a drawing using the Sub-D connectors. Take a knife and cut it out. Now you can set marks on the case so that you know where to screw holes in. For the holes, use the drilling machine and saw. Then work it out with the file until the sub-D fits in. Do this for all sub-Ds and screws, and the last thing you should do on the case is file out a hole for the cable.

Take the circuit board and solder in the IC-socket, then tin the contacts for the cable. Put the IC in. Prepare the cables: We need one 9-lined cable for the userport (about 70 cm), two 5-lined for internal joystick connections (about 8 cm, important: they should have the *same* length) and one single-lined cable (about 10 cm). De-Isolating and tinning the cable-ends beforehand makes work later on much easier.

Connect the cables then (see pictures). The best order in soldering the cables is Joy 1, Joy 2, Userport. Then Chip Select (CS) to Ground (GND). Now you can close the case around the userport connector, but mark the upper side!! Plugging it in upside down can harm the C64.

Now you're almost through! Test the interface: Deplug the powersupply, plug two joysticks to the interface, and then the interface to the C64. Power it on and run the JoyTester. If something is wrong, turn it off at once, deplug the interface and test the connections with a checksummer (always before the IC). Fix the sub-Ds first, then the circuit board. To ensure a long life for the interface, put some isolation tape inside both cases where the userport-cable is leaving the case. Test everything again and repeat previous steps until all directions and fire buttons work.

Now have fun!!

Using the 4 player interface in your own productions
Next to providing more joy for you and your friends, Protovision designed the 4 player interface with the coder in mind. Programming the interface and thus using it in your own productions is very simple! Let's take a look at this source code! It represents a driver for the connected joysticks.

First, initialize the driver by calling the INIT function. From then on, you can call the READ function to get values from all the joysticks - those connected to the Protovision 4 Player Interface and the ones connected to the standard C64 control ports.

This implementation only uses the accu and stores the 4 joystick status values to the label PORT. All the 4 values have the same pattern for the joystick direction and fire button status. This means that they can easily be checked, for example in a little loop.

Look at the comments in the source code to see how it's done!
PORT
    .BY $00,$00,$00,$00

INIT

    LDA #$80
    STA $DD03 // CIA2 PortB Bit7 as OUT
    LDA $DD01 // force Clock-Stretching (SuperCPU)
    STA $DD01 // and release Port
    RTS

READ

    LDA $DC01 // read Port1
    AND #$1F
    STA PORT+$00

    LDA $DC00 // read Port2
    AND #$1F
    STA PORT+$01

    LDA $DD01 // CIA2 PortB Bit7 = 1
    ORA #$80
    STA $DD01

    LDA $DD01 // read Port3
    AND #$1F
    STA PORT+$02

    LDA $DD01 // CIA2 PortB Bit7 = 0
    AND #$7F
    STA $DD01

    LDA $DD01 // read Port4
    PHA // Attention: FIRE for Port4 on Bit5, NOT 4!
    AND #$0F
    STA PORT+$03
    PLA
    AND #$20
    LSR
    ORA PORT+$03
    STA PORT+$03
    RTS

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