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Forum: FPGA, VHDL & Verilog Audio Interfacing with FPGA


Author: Jack Born (Guest)
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I would like to connect 3.5 mm audio jack to nexys 3 board but have no 
idea how to do so.. I am a beginner with regards to fpgas and vhdl 
coding

Author: Lothar Miller (lkmiller) (Moderator)
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Jack Born wrote:
> I would like to connect 3.5 mm audio jack to nexys 3 board
Why? For what reason?

> but have no idea how to do so..
Fist step has absolutely nothing to do with FPGAs or VHDL: you must 
connect an AD converter to the FPGA.

> I am a beginner with regards to fpgas and vhdl coding
Then don't start with such a fairly demanding task (for a beginner). 
Instead start with the "blinking led", the "chasing light", and some 
RS232 and VGA, just to learn the very basics of hardware design. If you 
do not, you will crash...

Author: Jack Born (Guest)
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Yes I was thinking of buying an ADC converter as the one shown.  I know 
it sounds noobish but am not sure how to connect the audio jack's left 
and right channels to the respective data 1 and data 2 pins.

Author: Lothar Miller (lkmiller) (Moderator)
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Jack Born wrote:
> not sure how to connect the audio jack's left and right channels to the
> respective data 1 and data 2 pins.
Not at all. Read the documentation for the ADC module, then you will see 
that you have to connect the audio source to P1 and P3. Data1 and Data2 
are the digital serial ADC outputs.

: Edited by Moderator
Author: Jack Born (Guest)
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But how can a 3.5 mm jack be connected to 2 ports simultaneously?

Author: Lothar Miller (lkmiller) (Moderator)
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Jack Born wrote:
> But how can a 3.5 mm jack be connected to 2 ports simultaneously?
It may be a stereo jack...
http://en.wikipedia.org/wiki/Phone_connector_%28audio%29

Author: Jack Born (Guest)
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yes but how do i connect the stereo jack with the adc converter shown in 
the picture?

Author: Lothar Miller (lkmiller) (Moderator)
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Jack Born wrote:
> yes but how do i connect the stereo jack with the adc converter shown in
> the picture?
Get a soldering iron and start. Maybe you must add a offset voltage to 
get the audio signal into mid range of the adc input:
The AD1 converts an analog input signal ranging from 0-3.3 volts 
to a 12-bit digital value in the range 0 to 4095.

So you will need something like this here:
                o
                |
               10k   
                |
In Left   --||--o---- P1 of ADC
         470n   |
               10k   
                |
               GND

In GND ---.
          |
         GND

                o 3V3
                |
               10k   
                |
In Right  --||--o---- P3 of ADC
         470n   |
               10k   
                |
               GND

> with the adc converter shown in the picture
Its an AD1 module from Digilent. Just WRITE down this little fact 
instead of digging in the mud for over 2 hours just to find out a little 
snippet of information...

Author: Jack Born (Guest)
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actually thought i couldn't mention any brands, thanks I will dig around 
a bit and let u know how I got off

Author: P. K. (pek)
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Maybe this could be a solution for you (ADC included...):
http://uk.farnell.com/digilent/210-191/peripher-mo...

Author: Jack Born (Guest)
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thats converting digital to analog not analog to digital :/

Author: uwe (Guest)
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Author: Hobbyorganist (Guest)
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The Nexys has 4 PMOD connectors. There are a number of audio IFs out to 
purchase in PMOD standard from Digilent.

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