This is going to be a walk-through of how I built my usb pedal boardout of an analogue joystick (written as I did it), to use with my 'Niall's Pedal Board' program. To be honest, most of it will probably be different if you're using a different joystick to the one I chose, and I'm sure there's a better way to do it, but hopefully this'll be of some help. If you're basing your board on this walkthrough, I'd recommend you read through the whole thing before you start, so you've got an idea what you're going to need, and to make sure you understand what I've written (I'm bound to have missed out some important detail or something). Here's an example of what the finished product will (hopefully) look like:

Note : All the prices and shops referenced will be British, I don't know the equivalents for the rest of the world.

Contents
- Choosing a Joystick
- Choosing the Components
- Building the Enclosure
- Building a Pedal
- Taking the Joystick Apart
- Attaching the Switches etc.
- Conclusion

Choosing a Joystick
Okay, what you're looking for here is an analogue joystick. Digital ones won't be much use, because we want to use the axes of the joystick as expression pedals. You probably want at least 4 buttons as well, so you can have a good number of buttons. The good thing about most of the analogue josticks I saw when I was looking is that they tend to have a throttle control as well, which essentially means you have 3 analogue axes on your joystick. It's probably a good idea to go for a joystick with quite a large base and handle as well - this means it'll probably be easier to get at the circuitry inside, which is what we're really interested in. Another thing you should look for is that the joystick is held together with relatively ordinary screws (not weird triangular ones or something) - otherwise you may have to resort to attacking it with a hammer to get at it's insides.

I chose a Logic 3 Star Fighter joystick, from Maplin. It cost me £14.99 (this seems to be the cheapest you can buy a joystick for, although I didn't look on the internet), and has 3 axes (horizontal, vertical, and throttle), 4 buttons and an 8-way POV hat. To be honest, I can't actually think of anything to use the POV hat for - I'm not sure there's any need for a circular control like that on a pedal board. It's also quite big, so it should (theoretically) be easy to get at it's insides. What it looks like:

From the side:

Choosing the Components
Basically, all I needed to buy was 4 switches and 3 potentiometers (I could have probably used the pots in the joystick, but I figured buying my own gave me a bit more freedom). For the switches I chose 2 locking foot switches (no. N84AR from Maplin), and 2 momentary foot switches (no. N85AR from Maplin). For the pots you'll want to match them to the pots on your joystick - mine used 3 100k pots, so that's what I bought.

Building the Enclosure
Now, first you want to work out what size and shape you want the board to be. I decided I wanted 3 expression pedals and 4 buttons, so basically I want something that's 7x the width of my feet, if I'm going to be able to use it without accidentally hitting the wrong control. You probably want something that'll be able to take your full weight if you stand on it, so you're going to have to make sure you brace the enclosure somehow. I'm building my pedal board out of wood for the most part, because my Dad's always got a pile of scrap wood I can use sitting in his garage and, well, I wouldn't know where to start if I built it out of metal. Here's a picture of the initial box, from below so you can see all the bracing:

The picture's taken from the back of the box, so you can see the hole at the near side for the usb cable to come out. Basically there's not much to the enclosure, it's just a big box. I used plywood for the top, because it's thin enough that I can get the switches through and mount them properly. I can't remember what the wood I used for the bracing is called - it's similar to plywood but thicker, and a bit more sturdy. As for the height of the braces, I just measured the height of the base of the switches and made it a bit taller than that. You probably don't want to make the box too high if it's going on the floor. To attach the various bits of wood together, I used wood glue, and panel pins to hold them while the glue sets.

Building a Pedal
This is the hard part - you have to be very careful lining everything up here, or it won't work right and you'll have to take it all apart. The first thing to do is build yourself the paddle part. Here's what one of mine looks like:

You're probably going to have to shape the barrel of your pot as well (mine came with a cylindrical barrel, which isn't going to catch on anything properly). The simplest thing to do is probably to make the barrel roughly rectangular. Here's a photo (it maybe doesn't show the barrel of the pot too well, but hopefully you've got the idea):

Next you want to cut yourself a small block of wood which is going to be attached to the bottom of the paddle, as well as the barrel of the pot, so that when you rock the paddle, the barrel turns accordingly. What I did was cut part way down the middle of the block of wood, then use a small file to make that slot just large enough that the rectangular barrel of the pot could squeeze in. You want this to be a tight fit, or you won't get a particularly good response from your pedal when you try it out. A picture (including the file I used):

Don't attach this block to the paddle yet, you'll want to make sure it's lined up correctly first. Now you want to attach some braces to the main box, to hold the pedal up. I used 50mm metal corner braces from B&Q (part no. H29453?). Make sure you have them lined up with each other, or you'll run into problems. Once you've done this, you'll want to put the paddle in place, and mark the points on both sides where you're going to have the screws that'll act as it's axis. Once you've done this, work out where pot is going to sit. It is very important that the barrel of the pot is lined up exactly with the line of the axis screws - if it's not, the pot may get lifted out of it's mounting at certain rotations, or you may not be able to move the pedal it's whole distance. Mark where the pot is going to sit on the main box. Now it's time to build something to hold the pot in place. I did this by using a small piece of plywood with a notch cut in it for the pot to sit in, and attaching the plywood to a thicker piece of scrap wood which is then attached to the top of the main box. This picture should illustrate what I mean:

Now that that's done, and you know where the pot's supposed to be, you can attach the earlier block to the paddle, like so:

After that, it's just a matter of attaching the pedal to the main box, and putting in the 2 screws to attach the paddle to the braces. Remember to solder some wires to the pot's tags before you sit it in place. I drilled a small hole in the top of the box for the wires to go through. Here's what the pedal should look like:

Remember to screw the pot to it's mounting as tightly as possible, you don't want it moving when you rock the pedal. Here's a picture of the board with the 3 pedals and 4 switches (with the switches, it's just a matter of drilling the correct size holes for the switches (I used a 13mm drill bit) and screwing the nuts on):

Taking the Joystick Apart
Now, get your screwdriver and start taking the joystick apart. Depending on what joystick you're using, this may or may not be a simple task. For mine, I had to hack at the plastic base to get the circuitry from the top of the stick. Remember that you want to keep all the circuitry intact - there's usually some (relatively) complicated electronics going on to convert the relevant signals to a suitable format to send them along the usb cable. Here's what I got when I'd removed the circuitry from the plastic body:

The white-ish plastic bits are the pots from the base of the joystick - I later removed them. The black plastic thing caused me problems (I couldn't get a grip on it to saw it in two), so in the end I just left it there. The circuit board towards the top of the picture is the main board that resided in the joystick's base, while the smaller one was in the head(?) of the joystick, for the 4 buttons and the pov hat.

Attaching the Switches etc.
For this it's just a matter of connecting up your pots to the wires that connected the joystick's ones. As long as you connect the same wires to the same tag on your pot, you should be ok (I just cut the old wires near the old pots, stripped them, and soldered them to my new wires). For the switches you want to solder them the same tracks as the switches from the joystick. How you do this is up to you. My joystick came with quite generous solder blobs holding the original switches in, so I just melted them with my soldering iron, and attached the new wire there (it saved me having to try and remove the old switches). It's a good idea to first test which way the switches are connected - I think some joysticks are set up so that a 0 (0V) is on, while others (like mine) are set so that a 1 (~5V?) is on. Here's a big picture of what the inside of my board looked like at the end of all this soldering (yes, I did just fix all the wires in place with insulating tape):

Conclusion
Once everything's connected up, you'll want to attach it to your computer and test it. First you'll have to go to Control Panel->Game Controllers and calibrate it again, because the pots (and angles) you've used are unlikely to match up with the ones on the joystick originally. You can also test whether you've accidentally wired up any momentary switches wrong here.

To be honest, this turned out to be a far more complicated engineering task than I had first thought it would be, and the pedal board I made isn't exactly the sturdiest thing you'll ever see. I wouldn't really want to put my full weight on it for fear of breaking it. The 3 pedals also are far higher than a normal pedal, with a greater angle of rotation, which is bound to give my ankles a good workout. As well as this, the pots seem to give a very coarse range of values on the computer. I don't know if I could have avoided this by buying more sensitive pots, or if it's something to do with the circuitry of the joystick I used. Having said this, I can now play my guitar using my laptop as a pedal board, and I didn't have to fork out, what, £600? for NI's Guitar Rig, so I'm happy.