Re: [sdiy] ADC/DAC to Microprocessor for Audio

[Roman]

with pic18 you better stay with 8bit ADC/DAC, because running 16-bit or 24-bit precision arithmetic would eat a lot of MIPS.
So if it's 8-bit ADC/DAC what you want, try www.maxim-ic.com for ADC samples. Same applies to DAC, but you may also make R-2R DAC by yourself. The sound quality is low anyway at 8 bits.
For filtering I'd suggest switched capacitance filters also from Maxim. 8-order filters in DIP8 package. For your application more than enough. Simple smoothing filter at the DAC output, may be the same filter too, although it's not essential here. You are doing it only to learn DSP, right?

Anyway I suggest trying real DSP. They work natively with 16-bit and more, have direct interfaces to commonly used ADC/DAC, are faster than any PIC, and regarding to your last question - they have sometimes 8-bit wide "carry bit equivalent" for overflow situations, and they can also saturate the result and not wrap when exceeded word size.

hope that helps

Roman

---- Wiadomość Oryginalna ----
Od: William Berzinskas 
Do: synth-diy at dropmix.xs4all.nl
Data: Mon, 15 Nov 2004 22:38:23 -0500
Temat: [sdiy] ADC/DAC to Microprocessor for Audio


Looking over the net,  it seems the general consensus is to not try what i want to do..  but all that aside..

What circuitry is need to go into a adc and out of a dac for use with audio and a pic18?   most likely, the adc/dac would be single supply (i'm mostly limited to dip here)..  so, i'd need to deal with that..  

also what kind of input filtering is necessary?   and whats this about output reconstruction filter?    



On a side note..  I've tried some simple stuff like this before, but no good results because the aforementioned were not handled..  just trying to sample and output data..    one thing i noticed.  for instance: if i was working with 8 bits..  how would i handle situations that caused an overflow?  is there some averaging of bits here or something i should be aware of? 

thanks in advance
--billie blaze