[sdiy] Atmel ATxmega32A4 (and 64A4, etc.)

[Joe Grisso]

On Sat, Feb 12, 2011 at 1:57 PM,  <lanterma at ece.gatech.edu> wrote:
> On Feb 12, 2011, at 12:04 PM, Joe Grisso wrote:
>
>> The xmega series is quite an awesome processor. I've been using the 128A1 for my touch sequencer project, and it's definitely lived up to my expectations. One word of caution: The DAC module will have up to 20mV of low-end offset for the processor. While the converters are not as nice as dedicated ones (INL of 5 LSB, having to manually trim or auto-calibrate the output offset with bipolar supplies), they definitely do well for most average musical applications.
>
> Would one be better off just using a MCP4822 or MCP4922?

The quick answer is "it depends"

For me, it seemed like an inelegant solution considering all I needed
to do was offset and scale the DAC output in order to get the desired
output and accuracy. The alternative would be to include SPI handling
code into the MCU as well as extra hardware to support a $2 DAC that
only gets me a better INL. That's extra cost and complexity for a
simple chromatic quantizer. But, I can see the use for it if tighter
INL is needed, or even if the MCU needs to be located far away from
the analog interface. The SPI lines can be ran to the converter and a
ground moat can isolate analog from digital signals providing for a
quieter analog subsystem. I think in the DIY realm an external DAC is
easier because you don't have to mess with so much of the innards of a
processor. SPI is well understood and there are more people who would
have experience with any debugging required for it rather than an
on-board DAC.

Best,

-- 
Joe Grisso
Detachment 3, Ltd.