Now that we have a pretty good idea of what the internals for the Module 1 will be, let’s take a look at the faceplate. As mentioned earlier, it will be built around an iPod Touch, which will be mounted in landscape orientation. Knobs and female connectors for our 8 polyphonic channels will be laid out with 4 channels on each side. Every monophonic channel will include the following:
- One set of dual concentric control knobs
- One 3.5mm jack for input
- One 3.5mm jack for output
- One 3.5mm jack for input voltage control
- One 3.5mm jack for output voltage control
As a result, 6 analog endpoints will need to be mapped. We also have 30 pins to map on the Arduino side (Cf. article), bringing the total to 36, which is 4 too many if we wanted to use a pair of AD75019 analog crosspoint switches per channel. That being said, we could make the I²C bus and a set of 4 digital inputs/outputs mutually exclusive with some simple digital switching.
Doing so, we could simply cascade our pair of analog crosspoint switches in a 32 × 16 configuration, allowing any of the Arduino pins and any of the channel endpoints to be mapped to any of the 16 endpoints provided on the channel breakout board. This architecture would then require a total of 16 AD75019 switches.
As a sidenote, I should mention that using dual concentric control knobs is aimed at reducing the amount of real estate required by each channel on the faceplate, the goal being to keep our module as small as possible, so as to use as little space on a rack as possible.