         How to build a Multi Joystick Interface for youself
         ===================================================
         
         
         Introduction
         ------------
         
         There are two ways of building a Multi Joystick Interface. You
         can etch a printed circuit board and simply solder all com-
         ponents to it, or you can do it the old fashioned way with
         lots of wires. 
              ETCHING.DOC is intended to be of some help if you decide
         to go for a printed circuit. It is also intended to suggest to
         you that etching is worth the extra effort. Soldering is a
         piece of cake with an etched printed circuit board.
         
         
         The board size
         --------------
         
         For etching: a 53mm x 100mm piece of single sided board (one
         third of a 160mm x 100mm standard size board).
         
         If you don't want to etch: a board the size you like with a
         2.5mm drill grid. 100mm length on one edge is fine, as 3
         joystick connectors will fit along this edge and the other
         three along the opposite edge. Depending on the part density
         you think is favourable, the other edge will be about 60mm to
         160mm.
         
         
         The power supply
         ----------------
         
         There are three ways of supplying the interface with electric
         power: 
         
         The method we recommend is to connect the multi joystick in-
         terface to a surplus analogue joystick port on your computer.
         Of course, only the 5V and GND lines will be used. Obviously,
         you need a surplus analogue joystick port to do that.
         
         If you don't have any spare joystick ports, you will have to
         buy a small transformer of 8-20V DC or 6-22V AC, capable of
         supplying 250mA. The AC version of the interface features a
         rectifier and a second voltage stabilizer to cope with the
         (higher) rectified voltage.
         
         
         The parts list
         --------------
         
         (0) Basic parts list
         
           2 multiplier chips 74150
           2 chip sockets (24 pins)
           1 capacitor 0.1F
           1 electrolytic capacitor 100F/35V (mounted upright)
         

           1 centronics connector (female, 36 pins)
           1 resistor 330 ohms
           1 5mm LED, red (or whatever color you like)
           1 5mm LED socket
           1 20mm fuse socket (european type fuse, print variant)
             some 20mm fuses (250mA)
             some screws M3x15mm
             some nuts M3
             10cm flat cable (see "The Centronics connector" below)
           1 3.5mm mono connector, female
         
         Joystick connectors (don't miss "Fixing ..." below):
         
           6 sub-D connectors (male, 9 pins, print variant)
         
         (1) Joystick port power supply version:
         
           all of (0) and additionally
           1 sub-D connector (male, 15 pins in 2 rows)
           1 3.5mm mono connector, male
             1m-2m stranded wire (2 strands)
         
         (2) DC transformer power supply version:
         
           all of (0) and additionally
           1 voltage stabilizer 7805 (1A)
           1 diod 1N4001
         
         (3) AC transformer power supply version:
         
           all of (0) and additionally
           4 diods 1N4001
           1 voltage stabilizer 7815 (1A)
           1 voltage stabilizer 7805 (1A)
           1 capacitor 0.1F
         
         Total cost should be about DM50 or US$30.
         
         
         Fixing the joystick connectors
         ------------------------------
         
         As only few joysticks plugs fit easily, while most require
         some small force, you should fasten the joystick connectors to
         the board with screws. Take care that the connectors are
         suited for screwing them to the boards. Most connectors have
         weak clamps to fix them: These clamps usually are too weak,
         but they can be cut with a pair of tongs (after taking the
         connectors apart) to make way for screws.
         
         
         Soldering
         ---------
         
         For the joystick port powered version, print PLCPLN1.PCL/PCX,
         if you want to use an AC transformer, print out
         PLCPLN3.PCL/PCX, if you want to use a DC one, print
         PLCPLN2.PCL/PCX. Solder in the joystick connectors first,
         then the chip sockets and the 330 ohm resistor.
         
         Joystick port version: Solder in the 0.1F capacitor and the
         wire connections.
         
         AC version: Proceed with the voltage stabilizers and the 0.1F
         capacitors.  Then insert the four diods. The white ring at the
         minus end shows the correct orientation. (Be quick when
         soldering the stabilizers and the diods - they can be damaged
         by too much heat).
         
         DC version: There's just one stabilizer, while the other one
         is replaced by a wire connection between the outer pins. The
         second capacitor is dropped. There is just one diod, too, and
         one wire connection. The white ring at the minus-end of the
         diod shows the correct orientation. (Be quick when soldering
         the stabilizer and the diod - they can be damaged by too much
         heat).
         
         Next, take four pieces of stranded wire of 80 mm length. Use
         two of them to connect the LED to the board. For correct
         orientation, remember that the rim at the lower end of the LED
         is usually flattened at the minus side. Connect this pin to J3,
         the positive pin to J4.
              Then, use the other two pieces of wire to connect the
         3.5mm mono connector (the power connector) to the board. For the
         Joystick port and the DC version, J1 is GND, while J2 is +5V.
         
         Joystick port version: Pin 1 of the analogue joystick port is
         5V, pin 4 is GND. Connect the joystick plug via the stranded
         wire to the 3.5mm plug and take care that 5V is at the tip of
         the 3.5mm plug.
         
         DC version: Plus is usually at the tip of a 3.5 mm plug. If
         you are unsure, use a voltmeter to determine the correct
         orientation. If you don't have a voltmeter, just try it out -
         if it's wrong, nothing will happen.
         
         AC version: It's AC - no orientation problems here.
         
         Last, solder in the 100F capacitor (labeled "-" on the minus
         side) and the fuse socket.
         
         
         Testing the power stabilization
         -------------------------------
         
         Now you can test if the power stabilization part of the inter-
         face works: Insert a fuse, connect the interface to the power
         supply and look for the LED. It it's lit, fine. If not, check
         if its orientation is correct. Between pin 12 and pin 24 of
         the multipliers you should measure 4.9V to 5.1V now.
         
         
         The Centronics connector
         ------------------------
         
         If you can, get a piece of flat cable with 8 strands for a 5mm
         grid as the drill holes in the etched board are 5mm apart. If
         you do only have the usual 2.5mm flat cable, cut it to a width
         of 13 strands and use each second so the used strands are 5mm
         apart. 

         The connection table:

             Board  Centronics (36pin female)          Comment
              J5              22/30                      GND
              J6               12                    paper empty
              J7               11                        busy
              J8                5                       data 3
              J9                4                       data 2
              J10               3                       data 1
              J11               2                       data 0
         
         Note: The flat cable tends to break if you just lay the board
         flat on the table and start playing. We recommend to enclose
         the board in some kind of case. 125mm x 70mm x 30mm is about
         the minimum size for such a case. A width of 65mm to 75mm is a
         must if you want to access all joystick ports without dif-
         ficulties.
         
         
         Testing the interface
         ---------------------
         
         Insert the multiplier chips, then connect the interface to the
         power supply and to the printer cable. Start Porttest (don't
         forget to tell Porttest if you don't use LPT1) and select
         "test all". You should see two columns of dashes now. Connect
         a joystick to each joystick port and move it into each direc-
         tion. Any move of the joystick should light exactly one P or
         B.
         
         
         Troubleshooting
         ---------------

         If you use a printed circuit, chances are good that you will
         never need this section.
         
         Problem: There are lots of Ps and Bs before I move the joys-
         tick!
         
         Solution: Probably the ground line is not connected so compu-
         ter and interface don't have the same ground voltage.
         
         Problem: All Ps and Bs are dead!
         
         Solution: May be a worse case of the next problem, so see
         below. If you are lucky, you just forgot to tell Porttest
         about LPT2.
         
         Problem: About half of the Ps and Bs light willingly, but the
         other half is dead.
         
         Solution: a) the power supply of one of the multipliers is not
         connected. Check if pin 24 missed the socket or the soldering
         of the socket's pin is bad. b) the input line to the Centro-
         nics connector is not connected. Check pin 10 of both multi-
         pliers, the wire they are connected to and pin 11 and 12 of
         the centronics connector.
         
         Problem: Some joystick movements don't light a P or B.
         
         Solution: Check the soldering of all pins of this joystick and
         the multiplier pins they are connected to. Perhaps a multi-
         plier pin missed the socket.
         
         Problem: All joystick movements light two Ps or Bs.
         
         Solution: Probably you shortened two address lines. Check pin
         2 to 5 of the Centronics connector and all lines they are con-
         nected to.
         
         Problem: Some joystick movements light two Ps or Bs.
         
         Solution: Probably you shortened two joystick direction lines.
         Check all pins of this joystick and the lines connected to it.


         Final Step
         ----------

         To honour our efforts and encourage us to continue our work,
         send a triumphant postcard to:

                Christof Ruch
                Rollplatz 19
                38678 Clausthal-Zellerfeld
                Germany


