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.

Although requested, neither of these units were sent for review, so I'll just give a mention of the information available.

Games Ace works on the Kempston function so it will be compatible with that option, it also has the bonus of including circuitry to output the sound to the TV where the volume can be controlled.

Vox Box is the same as the Games Ace but also includes speech synthesizer based on th allophone system. Sounds interesting.

STICKING TO THE BEST

Zap in style. John Lambert juggles with joysticks.

Joysticks are the most popular add-on for the Sinclair computers, not just for playing games but also for drawing, cursor control in word processing packages and for moving anything around the screen. The keyboard can be used for all of those things but it is so much easier with a joystick.

Choosing a joystick from the hundreds available is not an easy decision, but this guide will show you what to look for, and how to connect it to a Spectrum or QL.

Joysticks are generally all the same. They may be different shapes and sizes but they all contain a number of simple switches which get turned on or off as the stick is moved. That type of digital joystick was first used on a home computer by Atari and, therefore, is sometimes known as the Atari standard. All Sinclair machines use this type of joystick interface.

The switch used can vary a great deal. The cheapest joysticks, such as Quickshot 1, us a bubble which when compressed by the stick makes contact. Those can wear fairly quickly and cannot stand up to heavy use.

Next in price and strength are leaf spring switches where the stick causes two pieces of metal to make contact. Finally, the most expensive joysticks use microswitches. Those will last a long time and can easily be replaced should they go wrong.

Generally, you should buy the most expensive joystick you can afford as that way it should last a long time. Try to get one with a metal shaft in the handle - plastic ones break - and, if possible, try it out in the shop. The feel of a joystick is very important, some are sloppy and others require a lot of movement before they register.

it is within the interface that the complications arise. All interfaces have at least one Atari standard socket where the joystick is plugged in, but those vary in how they tell the computer when the stick has been moved.

Which type of interface you buy will depend on what software you want to use with it. The most common method is known as Kempston - named after Kempston Microelectronics who invented it. What that does is to configure the interface as part of the Z80 I/O map so that it can be read - to find what position the joystick is in - using the instruction IN 31.

Another method is for the interface to emulate the cursor keys - five to eight plus zero as fire. For obvious reasons that is known as Cursor.

The third method is known as Sinclair and emulates the six to nine keys, with zero as fire. That is based on Interface 2 from Sinclair. Why Sinclair wanted to bring out yet another method is anybody's guess!

The problem is that until you but the software you have no way of knowing which of those three methods it will use. Many programs give you a choice but unfortunately not all. The way to get round that is to use a programmable interface.

Those allow you to let each stick direction and fire represent a key on the keyboard. All games have a keyboard option and you just set the interface to the keys it uses. That also gets round the problem of game that do not use any of the three normal methods - Psion is very bad in that respect.

Unfortunately, programmable interfaces tend to be the most expensive, and in some cases can be very difficult to set up. For playing arcade games a Kempston standard interface is the most useful, and the cheapest. Some interfaces combine more than one method in the same box, but the more facilities it has the more expensive it will be.

Some joysticks offer extra facilities and you should take care when buying those. Although it is popular to have two fire buttons on a joystick, in many cases they are joined electrically and perform the same function, so it does not matter which one you press. Some joysticks, however, have two, independent, fire buttons and some interfaces can take advantage of this. That type of joystick can also be used with interfaces which normally only expect one fire button, and so are particularly worth considering. Care should be taken, though, as pressing the used button on some interfaces, will cause the computer to crash.

Another common extra is auto-fire, giving an auto repeat on the fire button.

In order to make their interfaces more attractive some companies add extras which are not related to joysticks. The best known is probably the Nidd Valley Slomo which lets you slow down the computer so that - in theory - the games are easier to play. Two other products, the Opus Discovery 1 disc drive, and the Mikro-Gen Mikro-Plus include Kempston compatible interfaces.

As far as the QL is concerned life is much simpler. The two control sockets on the back are already wired to emulate either the cursor keys and space, or the function keys. All you need to plug in a joystick is an adaptor which fits the control socket at one end and a standard joystick at the other. Joysticks are available which plug straight into the QL - ones that have a QL style plug rather than the Atari standard. The problem with those is that when you upgrade to a different computer you will have to buy another joystick, as it is unlikely it will fit the new machine.

Buying a joystick and interface can be a harrowing experience. Don't be afraid to try out half a dozen in a shop - and don't buy from a shop which won't let you experiment. Ask your friends and, of course, read the reviews in Sinclair User.

Games Ace
Company: Datel
Telephone: 0782-273815
Price: £10.99, £17.99 (with Quickshot II)

Kempston compatible interface. Allows the use of auto-fire joysticks and outputs sound through the television.