ComputerVoltageSources

> I was designing the front panel and thought that I should bring the
> I2C out to the front panel in an extension connector. That way I
> could add some external I/O in the future.

I'd just leave it on the CVS PCB. Add the I2C connections behind the panels
for adding functions and leave front panels for MIDI, serial port and analog
modular signals.

> Not knowing anything about I2C, I looked at the Philips page. While
> they have a lot of devices, I didn't find anything particularly
> interesting except some 8 bit in/out chips. They do have LCD
> controllers but they are for direct control of the actual panels.

Port I/O expansion is the most useful application of I2C in this context.
It will add more digital I/Os (gates).

Philips has some programmable LED flashers that could operate as self
running clocks, set them and forget them from the Basic Micro standpoint.

For memory and analog/digital conversion, SPI is the more common interface
and has a much larger selection of cost effective solutions.

> We could keep the display interface the same via MIDI.

Agreed.

> I would suggest we go with the proven MIDI design, get these modules
> built, and then begin to experiment with the I2C interface, either as
> two more I/O pins, or as an I2C bus. It might be interesting to pick
> up some of the Philips parts and see how well they work. If people
> decide later they'd like an I2C interface and it works reliably, then
> they can upgrade the LCD SUPPORT pcb. It's just a microcontroller,
> pins, and a regulator anyway.

I'd think of an I2C expansion as an addon to the CVS. There's no need to
spin the LCD Support PCB, just make a new PCB that attaches to the CVS.

> > In one of my job incarnations, i used an I2C bus and some PICs to
> > implement a portable conveyer belt system and i had to combine slave
> > PICs and memory devices running at different speeds. It was one of
> > those projects that worked robustly in theory and in testing but
> > hung in production only when i was on vacation!
>
> Yet another horror story.

I could tell you many. Don't even think about multimastering, long stubs on
the bus, or more than a handful of slaves.

John Loffink
The Microtonal Synthesis Web Site
http://www.microtonal-synthesis.com
The Wavemakers Synthesizer Web Site
http://www.wavemakers-synth.com