INTERFACITS - JOYSTICK INTERFACING INVESTIGATED

A comprehensive round up of the units available - checked out by our team of reviewers.

One of the first add-ons that a computer owner may contemplate buying is a joystick of some kind. The increase in control that this provides is of obvious benefit to the dedicated games player. In addition it is becoming increasingly necessary for some of the complex graphics packages that are appearing for the Spectrum. However if you have not yet taken the plunge and are now contemplating the purchase of some form of controller you have a difficult choice ahead of you. In essence, most of the actual joysticks are very similar, and your eventual purchase will be based upon personal preferences for shape, size, ease of use etc., but the biggest decision to make will be that concerning the vital link between your joystick and the computer i.e. the INTERFACE.

Interfaces allow the use of joysticks with compatible software, and although there is a great variety of material available for use with all the more common interfaces no single one will give you control over every game, unless, of course you opt for a PROGRAMMABLE INTERFACE. These claim to give you joystick compatibility with ALL software.

The Downsway Programmable Interface, which has been available for quite some time now, is at first sight rather a plain black unit which plugs directly into the Spectrum's rear expansion port. It measures 65 x 95 x 25mm and has a dual-position switch on the rear and a standard 9-pin joystick socket on the right side of the unit. This is one of the advantages that this interface has over some other units currently available, in that the keyboard is left uncluttered by control cables and therefore can be used in conjunction with the joystick. This gives the user a wide range of control options which can be a distinct benefit considering the handful of keys that some programs demand. A small instruction sheet provided with the interface gives all the information that is needed to make your joystick compatible with any program.

Programming of the interface can be achieved either prior to loading a game or after the game has loaded. This facility takes care of all those programs that have no detailed instructions on the cassette inlay. To use this unit is simplicity itself - with the dual position switch in 'program' mode press the key for the specified command and move the joystick to the appropriate position. Release joystick and key then repeat for all other movements. In essence that's all there is to it!

After programming (a few minutes work) switch to the 'play' mode and away you go!

In operation the unit performed perfectly and on the odd occasion when a mistake was made it was a simple matter to re-program the offending key without the necessity of going through the entire procedure again.

The FIRE command is independent of direction command and this means that FIRE has only to be programmed once, as opposed to the multiple movement/fire operations needed with some interfaces.

The unit was tested with several joysticks ranging from the cheapest to one of the most expensive available and it performed equally well with all, the only noticeable difference being a somewhat coarser movement with one of the cheaper joysticks. Of the many programs used with this interface only two gave any problems - keys could be programmed but pressing the fire button caused the game to restart. As it happens the particular games weren't intended for joystick use anyway!

In conclusion, if a joystick interface is high on your list of priorities then it may well be worth your while paying a bit more for the extra flexibility that this excellent little unit provides.

STICKING WITH ADJUSTABLES

There are now several different ways of hanging a joystick on to the Spectrum, and they fall into two distinct categories - the dedicated type, which uses fixed input/output locations, and the more recent programmable type, which can simulate any chosen keys when the joystick is moved. Andrew Pennell, is concerned with the second variety - devices which should, in theory, offer compatibility with all software. He examines products from AGF Hardware, Cambridge Computing, Downsway and Stonechip.

All four of the interfaces looked at allow one joystick (or two in the case of AGF) to be connected to the Spectrum, via the industry standard 9-pin, D-type connector. Any joystick used must be the switched type, and not the proportional variety as used on the BBC Micro, for example. These consist of one switch for each of the four directions, and one for the fire button. Diagonal movement is recognised by two direction switches being activated simultaneously.

AGF HARDWARE SOLUTION

AGF was the first company to produce a programmable joystick, and this device remains the only true hardware-programmable interface. It consists of a large, exposed PCB with four ICs and 13 vertical bars. The back of the PCB is covered with black plastic, and for that reason it looks much neater from behind! To program it, two crocodile clips for each direction must be connected to the appropriate bars. A self-adhesive conversion table is supplied to convert each key into the two required connections. A total of ten crocodile clips must be attached, and probably it's best to do this with the power removed. Ten 'programming cards' are included on to which can be recorded the plugging arrangements for your most popular games.

When first connected, the interface firmly refused to respond to the fire button on the joystick, no matter how it was programmed. A dismantling of the stick showed nothing wrong, but closer inspection of the interface revealed a truly terrible joint to one of the clips. Swift action with the soldering iron soon had it working. One would hope that the interfaces are tested before dispatch to customers. This exercise brought to light another unredeeming feature of the unit - the edge connector that plugs into the Spectrum is incredibly tight, and almost impossible to remove (faced with the same problem, our editor had to resort to deft use of his letter opener). It's hard to imagine any of this palaver being good for the Spectrum's connector, although removal should not be necessary very often as a carry-through connector is provided to allow any further accessories to be plugged in, piggyback style.

AGF actually provides two joystick sockets, but these are connected to each other. The company says that this makes it easier to take part in two-player games, but some may think it's just as easy to pass on a single joystick to the co-player. The sockets are mounted on the top of the unit and therefore the joystick's plug and cable stick straight up in the air - thus easily obscuring one's view of the television screen.

However, once the operation had been figured out and the fault corrected, the interface worked very well. Programming is pretty simple and quick, and is of course retained once power is down. A simple demonstration cassette is included but, even so, at £33.95 it does seem a little on the expensive side.

CAMBRIDGE INCOMPATIBILITY

The next interface in line was the one from Cambridge Computing, and this comes supplied complete with joystick. It's controlled by software, but requires a program to be loaded from tape first. In fact the program allows a library of data for each game to be stored on the reverse side, so each key pattern has only to be entered once. This does mean though that the tape must be run before play can begin. During the first programming sequence a problem soon became apparent - the whole machine 'hung' with the word 'OK' on the screen. It wouldn't even Break, so all that was left was to pull the plug out. Only after running through this loop again did the truth strike - your reviewer is one of the few to possess both a ZX Interface 1 and a Microdrive, and the Cambridge port uses one of the Microdrive I/O locations. Cambridge really has no excuse for this blunder, the Microdrive ports having been documented since the day the Spectrum was launched - take a look at page 160 of the manual, guys!

Interface 1 was removed for the rest of the test and that obviously means that the Cambridge interface will not work with any games that load from Microdrive. Once programmed, however, the joystick interface worked well, with either a normal stick connected, or with Cambridge's own. The latter has a second and independent fire button, which can be programmed to simulate a different key to the first. However, the only game to come to mind that needs two fire buttons is Penetrator.

To test the device thoroughly it was used on one of the toughest games for any joystick - Jetpac by Ultimate (your reviewer's normal rig being the Kempston non-programmable interface plus Competition-Pro joystick). Opinions on joysticks are very personal things, and one man's loathing is another man's love. However (to digress a little from interfaces) after playing with the Cambridge stick for some time it seemed to me the device somehow failed to make the grade. It's noisy and not very sensitive and the two fire buttons are quite small (in fact it seemed best to program them both to the same key). The shape of the case looks as if it is designed to be held in one hand and operated with the other, but cramp set in after a while and the only resort seemed to be to rest it on a table instead.

The Cambridge interface does have a carry-through edge connector, but if it is incompatible with the Microdrive it is possibly incompatible with most other add-ons too. That aside, it works well, the only hangup being the tape that needs to be loaded before use. It comes reasonably priced at £24.00 for the interface only, or £29.90 if the joystick is bought as well.

DOWNSWAY - IN REAL TIME

The Downs way unit is programmed in a very different way to the previous two - namely in 'real time'. There is a 2-way switch on the back of the unit, which is normally in the 'up' position for program mode. To program it, the memory in the interface must first be cleared - which is achieved quite simply by moving the stick to all its positions in turn, and pressing fire each time. This done, each of the eight positions may be programmed by the holding down of the relevant keys and the moving of the joystick to the required positions, each time letting it return to the centre position. The instructions say that the diagonals should be programmed first, but it seemed to me that any order would do, provided the fire button is left until last. A total of nine positions are required, and the diagonals in particular can demand a lot of finger dexterity as you press two keys with one hand and hold the stick exactly diagonal with the other.

Once programmed and switched back into the play mode, you're ready to start. However, one great advantage with the device is that the interface can continue to be programmed after a game has been loaded, and therefore any mistakes can be corrected as you go along.

The Downsway interface is easy to use, quick to program and also the cheapest, at £22.95. My only quibble is that there should be an indicator label near the programming switch.

STONECHIP DEXTERITY

The final interface to come under scrutiny, by Stonechip, at first glance seems very similar to the Downsway one. It's programmed in the same way, the only apparent difference being that there is a 3-way switch - selecting normal, program or play modes. However, in use it proved to be rather different to the Downsway device. When in program mode, the Spectrum behaves strangely. It makes unusual buzzing sounds, and the border flashes. But the sequence of operations to program it remains the same, although with the one important difference - twice as many operations are required, as the joystick has to have all eight positions programmed once with the fire button pressed and again with it released. As well as taking some time, the task proved not an easy one. To program each diagonal with fire held down requires three keys to be pressed with one hand while the other holds the stick diagonal and presses the fire button. And now, with my teeth...

As with the Downsway unit it can be re-programmed after a game has been loaded, to correct any errors - a useful facility. Once all is ready the unit must be switched to the play mode for the joystick to be able simulate the keys. But this in itself presents problems for now you will notice that no keys on the keyboard work, and the ear socket is disabled. That means programs will not load and the switch has to be continually flicked back in order to re- enable the keyboard and thus allow the choosing of options from menus.

The Stonechip interface seems to offer similar facilities to the Downsway one, but with several disadvantages to weigh against it. It's also more expensive, at £24.95.

MODUS OPERANDI

How do they all work? Well, the Spectrum keyboard is based on an eight by five matrix, and was designed to be as simple as possible to read electronically. The AGF interface duplicates the matrix, but instead of having keys on it you can connect each directional switch at a particular point to simulate any key. This is electronically quite easy, but difficult to manufacture because of the matrix connections. The other interfaces are all basically similar to one another, showing just minor differences. They each contain 1K of RAM, not (as normal) in the memory map but in fact in the keyboard I/O space. This enables them to be programmed, ie. have the RAM written to, and then simulate the keys when they are read.

The actual method of switching between modes differs widely between the three. Cambridge uses another I/O port as a switch whereas the others just use a switch. The Stonechip design only has three ICs, excluding the RAM chips, but one can't help feeling that too many features have been cut to reduce the chip count.

TAKE YOUR PICK

In conclusion, it's worth the potential purchaser first deciding whether a cheaper, dedicated interface will suffice. There are three main types, produced by Kempston, Sinclair and AGF. If it will not, then choose the method you wish to use to program it - hardware, software or real-time. My personal view is that the Downsway unit takes the chequered flag, being cheapest and most easy to use.

However, the AGF interface may be worth the extra expense for those preferring something that's hardware programmed - even if, as in this case, the result is a little unsightly.

REC. PRICE: £22.95

PROGRAMMED BY: Real-time

COMMENTS: Can be re-programmed with game in progress, easy to use and quick to program, very reasonably priced.

DOWN YOUR WAY

Downsway proves the point that not all programmable joystick interfaces have to be big and bulky. The unit plugs into the edge connector port of the Spectrum and could be mistaken for a neat rampack if it were not for the 9-pin D plug protruding from its side and a two position slide switch. What is quite astonishing is that there is no logo or maker's label to identify the unit, which is pushing the incognito image a little bit too far. No instructions are provided with the unit, so beginners may have to solve the riddle by process of elimination.

OPERATION

The interface must be programmed from Basic. The slide switch is set to programming mode (Upper position for lack of annotation). Each individual joystick function is programmed in turn. The joystick lever is activated and at the same time the appropriate key pressed on the keyboard. Care must be taken to ensure the level is released before releasing the key on the keyboard, as the memory stores the actual data on release of the lever. Once this operation has been completed for all the functions, the slide switch may be returned to the normal position. The function of the joystick may now be checked and the correct characters should appear on the screen when activating the joystick.

The Spectrum is now ready for the game to be loaded. Atic Atac is taken here as an example. This game has provision for Kempston, Cursor or keyboard control. Either Cursor or keyboard control may be used in combination with the Downsway interface.

Keyboard control will be chosen and the joystick controller programmed for left, right, down and up using Q, W, E and R and fire action with T. Having checked the individual actions in Basic, the game is loaded and the keyboard control selected (option 1). On play, two things become apparent. First the good news, the fire action, although programmed only individually, will work even when activating a direction control. The bad news is that the diagonals do not oblige in a similar manner; they will not operate unless they are programmed beforehand. The same programming procedure as with the other directions applies, only that two movement keys will have to be activated at the same time while holding the joystick lever in a diagonal, so depressing Q and R keys the joystick must be pushed into the upper left diagonal and released.

In fact the standard procedure will be to program the 4 diagonals first and then the 4 main directions followed by the fire action. A snag will occur when trying to check the programmed functions, as Basic will not register two keys activated simultaneously and therefore the diagonals cannot be checked. If an error has occurred, it will only be noticed after loading the game and this means having to reset the Spectrum and restart the procedure. With a bit of practice, however, this should not occur. The fact that the programming has to be accomplished in Basic requires the function keys for the game to be known beforehand. In most cases this information will be found in the cassette inlay. During the period of the test, the Downsway unit performed faultlessly and without any side effects.

CONCLUSION

The Downsway interface is a very compact and effective programmable joystick controller. The lack of programming instructions complicates the initial use, especially since there is no annotation of the slide switch.

As with most of the soft or hardware programmable interfaces the programming is required to be done before loading the game and requires a little exercise, but apart from this drawback the unit proves to be far more versatile than any of the standard interfaces and provides a joystick facility for any game on the market.