[sdiy] I2C DAC

[Eric Brombaugh]

On 06/19/2010 02:09 PM, MTG wrote:
> I'm almost out of pins, but I have two left in a project that I want to
> hook a DAC up to for control voltages. Anyone recommend a decent I2C
> single or multi-channel 0 to 5v voltage out DAC? What are most people
> using for resolution of control voltages these days? I know 7-bits was
> the standard for a long time. Is it worthwhile looking at higher
> resolution for things like filter cutoff or pitch bend or ... ?

I think you'll have a hard time finding something as low as 7-bits 
resolution. 8 is pretty common, but for CVs is a bit coarse. 12-bit 
resolution will cover most CV applications without too much in the way 
of zipper effects and can even be used for reasonably accurate 1V/Oct 
scaling.

What processor are you using? Does it have a hardware I2C capability, or 
will you have to bit-bang the low-level protocol? I2C can be a bit 
tricky due to the built-in acknowledge cycle, and somewhat slow to 
update due to the relatively low clock rates. On some MCUs the pins 
available for I2C ports are limited due to the open-collector drivers 
required so you may not be able to arbitrarily reassign them.

Eric