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mux/demux schematics for an ADC/DAC setup?
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loss1234



Joined: Jul 24, 2007
Posts: 1536
Location: nyc
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PostPosted: Mon May 18, 2009 9:56 am    Post subject: mux/demux schematics for an ADC/DAC setup? Reply with quote  Mark this post and the followings unread

hey there

i am interested in trying to learn how to setup a multiplexer to send say 8 sources into a converter which then processes them and sends them out as 8 sources via a demultiplexer.

however..i do not want to send the commands to the multiplexers with a microprocessor. i would like to just stick to Cmos or TTL. i assume i will need a clock seperate from the converters clock but after that i am a bit lost. i know i hook up my 8 ins to the mux and my 8 outs to the demux.


i would like to understand it well enough that i could do it with any converters,etc.

can this be done? has anyone done it? are there schematics around? or ANY ANY good books to buy on how to do this sort of stuff?

i am interested in this for storing patches, routing DATA, etc.

so many schematics i look at just have a big processor.. or they just show the mux not the demux.

anyway...thanks for any help

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DrJustice



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PostPosted: Mon May 18, 2009 11:59 am    Post subject: Re: mux/demux schematics for an ADC/DAC setup? Reply with quote  Mark this post and the followings unread

loss1234 wrote:
...however..i do not want to send the commands to the multiplexers with a microprocessor. i would like to just stick to Cmos or TTL. i assume i will need a clock seperate from the converters clock but after that i am a bit lost. i know i hook up my 8 ins to the mux and my 8 outs to the demux.

Why do you not want to use, e.g. a microcontroller for this? Building it all from TTL/CMOS logic ICs will be a complex and expensive affair. This is a perfect example of a circuit for which one would use a microcontroller. There are several advantages to this: simplicity, flexibility, size, price, debugging (just load up new firmware instead of building a new circuit when there's a problem/error) etc.. You can get free development tools for practically all microcontrollers on the market; the firmware is typically written in assembly or C/C++, but there are also solutions that use variants of Forth or BASIC. One could also use a programmable logic chip (CPLD or FPGA), but this requires familiarity with logic design.

Quote:
can this be done?

Yes.

Quote:
has anyone done it?

Probably, in the old days before microprocessors and microcontrollers were available.

Quote:
are there schematics around? or ANY ANY good books to buy on how to do this sort of stuff?

Code:

        +-+-+----------+++  +++----------+-+-+        +-------+ 
        | | |          |||  |||          | | |        |       | 
     +---------+       |||  |||       +---------+     | |\    | 
     |  A B C  |     +----------+     |  A B C  |     +-|-\   |
     |         |     | ABC  abc |     |         |       |  >--+--->
>----|0        |     |          |     |        0|---+---|+/
>----|1     INH|     |       INH|---->|INH     1|   |   |/   
>----|2        |     |          |     |        2|  ---     
>----|3     COM|---->|Ain   Aout|---->|COM     3|  ---
>----|4        |     |          |     |        4|   |
>----|5        |     |          |     |        5|  GND
>----|6        |     |          |     |        6|
>----|7        |     +----------+     |        7|
     +---------+          ???         +---------+
        4051                             4051

In the example schematic above, the "???" block is your conversion and control circuit. That bit could actually be a single microcontroller or programmable logic chip, possibly with external ADC and/or DAC chips. Only the sample and hold for output 0 is shown.

Quote:
i am interested in this for storing patches, routing DATA, etc.

That makes sense - this is how programmable hybrid synthesizers do it. BUT, they all use a microprocessor or microcontroller...

DJ
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