[sdiy] new project

[Ryan Williams]

hi all,

I've started working on a new project that I've been thinking about for 
a while now. It is a shift register based noise and CV source. similar 
to the wiard noise ring but more designed for CVs. It will have a 
 >=12bit DAC on the output. 3 ADCs for voltage control of the the number 
of bits on the output, VC control of feedback bit for the shift 
register, and optional external input to the quantizer instead of using 
the shift register.

so I had some question about what would be a reasonable amount of bits 
for the DAC.  the shift register is 8bits but since I'm using another CV 
input for reducing that to anywhere between 1 and 8 bits I use a lookup 
table to scale the output to a 12 or more bit DAC. I had planned to try 
it with a 12bit DAC but I've just realized that the lookup table could 
be used for other things besides reducing bits. if so then I think it 
would be better to have more bits? If I do decide on a better DAC then 
I'll switch to a bigger microcontroller but then it would be even faster 
so maybe thats not a bad idea.

new features just keep adding on... I originally had a simple all analog 
with a 4000 series CMOS shift register, but now it's planned to be run 
by a AVR uC running at 8MHz. the program flow is simple, just sample the 
n ADC, then shift register, then lookup the output value based on that 
input, then output to the DAC and repeat. the fdbk bit selection ADC is 
sampled at the same time as the n ADC but it's output goes to an 8:1 
multiplexer. I posted a schematic for the first page that has most of 
the quantizer circuit so far. I haven't tested anything, atleast not on 
this version of the circuit. It's just there to give an idea of what I'm 
trying to do. suggestions welcome. i'm still new at this:
http://www.sdiy.org/destrukto/temp/shift_reg_quantizer.pdf

ryan williams