Here is a nice little project for all you budding Musicians out there.
You may not know, but the WAV Trigger board has some great features that make it ideal as a MIDI Synthesizer. Here are the main features
Two of these features are very important for our MIDI Synth. Firstly, it's Polyphonic, which means it can mix and play multiple sound files at the same time - so when you press 2 keys on your keyboard, both keys play.
Secondly, the WAV files are numbered from 0 to 999 and are played via the MIDI protocol using not only the key pressed but also the channel number. The default channel number 0 will allow files 0 through 99 to be played, channel number 1 will play files 100 through 199 etc. Thus the channel number can be used to switch between "sets" of WAV files to play. You will see later how we can change the channel number.
The next item for our project, is the USB Host board.
Here we are using the USB Host Mini board loaded with the MIDI software. This board allows us to connect a USB MIDI device and outputs the MIDI data on its serial TTL port. This can be directly connected to the WAV Trigger board.
The USB Host MIDI software has a feature which allows us to change the MIDI channel number being output. After turning this feature on, you can use some of the unused input pins on the board to select the channel number that will be used (See the MIDI software page for full details). For this project we have used a Rotary BCD switch which will allow us to easily change the channel number and hence switch between instruments by selecting different sets of files.
We also need a few other components
|For a keyboard we found a nice and cheap AKAI LPK25 on Amazon which seems a popular choice|
|Some Speakers. Generic powered speakers|
|BCD Rotary Switch. Available from RS Components|
Putting it all together
Wiring is straigthforward. If in doubt refer to each products product page for more information.
For the BCD Switch, in order for the pins to be pulled down to 0V by default, resistors have been soldered to the BCD pins and linked to a common ground wire (Brown). The positive input wire (Red 3.3V) pulls each pin up to 3.3V depending on the switch position.
Download the three sets of WAV files that were used. MIDI Synth WAV Files
NOTE: Due to the very large size of the MIDI files, they have been compressed using Monkeys Audio and then zipped. A copy of Monkeys Audio is included in the download. The download is still 30MB in size
Lets see a video of it in action. Please excuse my complete lack of musical ability