connecting 8052 to adc and dac

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hi,
i was wondering how to connect an adc and a dac to a 8025 (DS89C420). do i
have to use the two UARTs or it's better to use the "raw" i/o pins? what i'm
trying to do is a sort of audio filter: the signal is converted in digital,
read by the 8052 (where the fx are applied), and sent to the dac.
moreover i'm using BB's PCM1802 as the ADC and PCM1744 as the DAC. the
problem is these are all stereo adcs and dacs. do anyone knows about
audio-oriented mono adcs and dacs?
thank you for your help, CAFxX.



Re: connecting 8052 to adc and dac

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You need to check some basic maths first.  The PCM1802 I believe operates at
96KHz sample frequency and 24 bits.  Assuming you can use a serial input
and take three lots of 8 bits for each 24bit sample then you need to
receive three samples every 1/96KHz secs or 8 bits every 3.5 microseconds.
That's pretty damn fast for an 8051 but within the speed of the DS89C420
assuming the serial ports can go this fast.

On this basis I would say bit bashing via raw i/o ports is definitely out
and your best bet would be the serial ports.

Ian


Re: connecting 8052 to adc and dac


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at

Off the cuff, this sampling rate and resolution sounds like one hell of an
overkill for audio. Audio CD's are sampled at 16 bits, I think, and not
nearly at such a fast frequency. Also, processing and re-outputting the
audio through a ADC at 96K doesn't sound realistic, although it might be
with a super-fast 8052. What are the norms for audio recording and
processing, in regards to resolution and sampling freq? -- Mike



Re: connecting 8052 to adc and dac
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operates

Audio CD's are 16 bits at 44.1KHz, but 24 bit @ 96KHz doesn't
sound unreasonable to me, for professional gear used in studios.

SACD, super audio CD for the home user, is 1 bit at 2.8224MHz,
yes MHz. That's even more information pumped through. I have
no idea what mastering equipment for SACD uses.

Anyway, I don't know what a fast 8052 can do here. Even if it
is capable reading/updating the ADC/DAC, what can be done
with the audio bits, in the time left...


--
Thanks, Frank.
(remove 'x' and 'invalid' when replying by email)




Re: connecting 8052 to adc and dac

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Except that 24 bits is a s/n ratio of 144db.
I wouldn't be able to make a piece of wire
have a s/n ratio of 144db (:



Re: connecting 8052 to adc and dac
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Me neither ;)

--
Thanks, Frank.
(remove 'x' and 'invalid' when replying by email)



Re: connecting 8052 to adc and dac

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Perhaps this is a product for people with very discerning ears ,~)

The poster did ask for suggestions.

Microchip makes a line of ADC's, and a simple DAC is just a bunch of
resistors. If the OP would be more specific about what it is he is trying to
accomplish, that would lead to better suggestions.

Mike



Re: connecting 8052 to adc and dac

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I thought he was quite specific. He wants a single channel of audio in,
apply effects to it in the digital domain and send the result to a DAC to
recreate analogue audio. The 24bit/96KHz bit only came about because I took
the trouble to look up the chip he said he was looking at using.

Ian


Re: connecting 8052 to adc and dac

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trying
took

I meant specific in terms of quality. I used to work in the toy industry and
"quality" often meant "barely intelligible".



Re: connecting 8052 to adc and dac

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Me too and it still is.

Ian



Re: connecting 8052 to adc and dac
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That's why they print the word bubbles on the packaging. Many toys, I
can't understand what the hell they are saying. If I see the word
bubbles, that gives my audio processing firmware a list of possibles
and with those in memory, I can always guess what phrase is actually
being spoken.

Re: connecting 8052 to adc and dac
first of all thank you for your replies.
as ian pointed out i just wanted to build a sort of multi-effect processor
for mono audio signals.
the adc and dac actually do have a 24/96 resolution (even 24/192 fot the
adc) but they also support 24/48 and 24/44.1 so i wouldn't mind that. the
problem simply was how to connect them (they all are serial, but they do
have the data pin, the data clock pin and the l/r clock pin (since they all
are stereo)).
i took a look at analog device's microconverters but their DACs only works
at 12bits. otherwise they would have been perfect. maybe there are other
solutions around but i didn't find them. if someone knows them...

thank you very much, CAFxX.

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trying
took



Re: connecting 8052 to adc and dac
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Yep, they're all stereo.  (Or they have multiple pairs!)

Why don't use choose a DSP that has built-in I2S ports?  In that case,
you might actually be able to do something interesting.

Another option is to use a simple CPLD that takes I2S in and gives you
parallel out, and parallel in to I2S out.  If you're clever, you can
figure out how to extract only one of the channels, and if you're even
more clever, you'll realize that you can grab the 24-bit data in 8-bit
chunks, so you don't need 48 bits of shift register.  If you do it
this way, you're also not wasting your micro's time bit-banging a
couple of I/O ports.

I still think a DSP is the right way to go.

--a

Re: connecting 8052 to adc and dac

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1bit @ 2.883MHz *is* 24bits @ 96KHz, that's what SACD uses.

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The 8051 the OP specified has a 30nS instruction cycle - it's the fastest
8051 around.

Ian


Re: connecting 8052 to adc and dac

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    Use an Analog Devices ADuC816 instead, it has both the ADC and DAC
onboard.  Or some other processor that contains both and avoid having to
interface separate components.

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