A small step today. I’ve removed the old bundle of cable and replaced it with a ribbon cable. Its a twenty strand flat ribbon, I’ve used thirteen strands for the keys and one for ground leaving six wires unused. I’ve left them as part of the cable on the grounds that they might come in for something later on.
The pedal board is ready with all the parts cleaned and screws tightened. I have a bundle of thirteen wires, one for each pedal. I’m planning to convert the input from these wires into a midi output. I’m using the Arduino Uno board to convert between the two. Rather than clogging up all the arduino inputs with wires I’m using a pair of PCF8574A port expander chips to encode the keyboard inputs.
The white wires in the above diagram are all inputs, sixteen of them, three spare. the diagram above was prepared using Fritzing, a fabulous open source tool for circuit design.
Here’s the result set up on a breadboard.
I’ll be testing this out with a few jump leads before wiring in the keyboard wires. Code next. Meanwhile, I’m thinking of replacing the bundle of cable with ribbon cable which would be easier to connect to the completed circuit board.
By the power of eBay, I have acquired this 13 key bass pedal, just what I needed for a bit of midi hacking. As it comes, this pedal is simply a set of thirteen switches. My plan is to add a midi output to the back of the box.
Inside, each key is switched so that as the pedal is pressed it connects to horizontal common bus running across the full length of the pedal. ( you can see it running across the botton of the brass coloured section below.)
Each switch then has its own colour coded wire running in the bundle, top left of the picture above.
Okay, so that’s the mechanics sorted out, next step, take the thirteen switches and turn them into a midi output. The Arduino, my choice for microprocessor comes with 14 digital inputs, one for each key and one for the output. Alternatively I might use an I/O expander chip such as the PCF8574AN then I’d have more inputs available for other switches and cool stuff.
I ordered the Sparkfun Midi Shield from Amazon for a bargain £15. The postman brought the neatly packed kit the next morning. Time for a bit of soldering. Sparkfun’s kit is designed to plug into your Arduino board ready for some MIDI programming. All the surface mount devices are already soldered into place. The remaining parts need to be soldered by the purchaser. Here’s what comes in the pack.
There are no instructions in the pack so here’s how I put it together.
Solder the two sockets into place, I used masking tape to hold them flat to the board as it was being fixed down.
I then soldered in the three switches and two rotary pots. There are a couple of large tabs on the pots. I soldered these down as well just to hold the pot into place.
To finish off, I dropped the shield into the pins and soldered it down.
Done! Next, testing.