Device Drivers & External Controllers

When your PC soundcard ceases to function, the newly connected external controller very often gets the blame — wrongly. Brian Heywood identifies some possible alternative causes.

One of the most common PC soundcard problems rears its ugly head when you try to connect an external controller, say a keyboard, to the external MIDI port. Most soundcards on the market were developed for the games market and are thus modelled on the Creative Labs SoundBlaster. They use a special cable connected to the joystick port to get MIDI into (and out of) the PC. So it's not surprising that when you get the bits and connect them to an otherwise functioning soundcard, the new kit tends to get the blame if the system doesn't work as planned. However, it is fairly unlikely that the external MIDI equipment is playing any part in the problem of getting MIDI into your Windows (3.1 or 95) system — there are a number of more likely causes.

Getting back to basics, for Windows to 'see' any MIDI device (either for input or output), you need to have a MIDI device driver installed. This software is almost invariably supplied on the software installation disks that come with the MPC soundcard or MIDI interface. What this device driver software does is provide a connection between the generalised Windows MIDI software interface and the hardware of your soundcard.

Err, Excuse Me...

This software has to be provided by the card manufacturer, as it is specific to the soundcard's hardware and can cause problems if it is not particularly well written. Even if the software is OK, you still come unstuck if the device driver is not set up properly. For instance, your soundcard could work perfectly under Windows — and even be able to send MIDI data — but not receive MIDI if the MIDI IRQ is not set correctly. This is because the incoming MIDI data is asynchronous (ie. unpredictable) and has to be captured by an interrupt handler, which is a part of the device driver.

An interrupt handler is simply a small piece of software that is run by the operating system whenever a byte of MIDI data is received by the interface card. The handler will only run if the hardware on the interface can send an interrupt to the computer's processor using an IRQ (Interrupt ReQuest) line, basically an electrical signal that connects straight to the PC's brain (ie. the CPU or processor). If this line is not configured properly, the PC has no way of knowing that MIDI data has arrived and thus won't read the data into memory.

On Route

Of course, there may be other reasons why your external MIDI controller isn't working: the MIDI cable might be broken or incorrectly wired, the game port on your soundcard might not be compatible with the de facto SoundBlaster standard, or the MIDI device driver supplied with the card may even have a bug in it. So you should check the following things to try and track down the problem...

• Check that the controller is sending valid MIDI data: find a friend or relation who has a MIDI keyboard, plug the keyboard into the MIDI In socket and play something. Alternatively, you could visit your local music shop with the MIDI keyboard underyour arm and say that you'd like to try outsome MIDI sound modules. If all else fails, purchase a BrightEye MIDI tester plug, which has an LED that flashes when plugged into a MIDI Out socket that is sending MIDI data (see the 'Bright Idea for MIDI Musicians' box, above).
• Check the lead connecting the MIDI keyboard to your PC. If you are using a MIDI lead, connect it between two MIDI devices known to be working or test the continuity between pins 4 and 5 on each plug (ie. 4 ‑> 4 and 5 ‑> 5).

Pins 4 and 5 are the second from each end — looking at the end of the plug with the index 'bump' at the bottom, the pin numbering goes in the order 1‑4‑ 2‑5‑3 from left to right. If you are using a converter lead that plugs into your soundcard's game port, then you could try using the same lead on another PC. Unfortunately, there is no simple way of checking this type of cable, and they are quite often the cause of this kind of problem. Yamaha sell this kind of PC cable for £15, so if you suspect that this may be the cause of the problem and you have no other way of testing it, it may be worth calling their Multimedia division (01908 366700) for a replacement.

• Check that you have the most up‑to‑date MIDI drivers loaded — contact the soundcard supplier or distributor; they should be able to supply a free update if one is available. You can check the current version and settings of the device driver by looking at the Drivers icon in the Windows 3.1 Control Panel or the Device Managertab on the Windows 95 System Properties dialogue. You need to open the 'Sound, video and game controllers' branch, then click on the Properties button of the soundcard device in Windows 95.
• Check that there are no clashes with other system resources. With Windows 95, you will need to do this manually (unless you have a 'Plug and Play' soundcard) by trawling through the Device Manager pages for other devices on the system. If there are no clashes, you will need to check that the settings match those made with the physical jumpers on the card. Most cards should come with a DOS‑based diagnostic program for checking that the card hardware is working and interfaced properly with your PC.

If you've run through all the above checks and you're still having no joy, then you may have a soundcard that is inherently incompatible with your particular model of PC. If this is the case, you should be able to return it to the original vendor as being 'not of satisfactory quality' and be eligible for either a refund or a suitable replacement under the Sale and Supply of Goods Act 1994.