How to input an analog signal to FPGA board for processing?
Vagant
I am a beginer and have a basic question.
My project implemented on FPGA board (which is Spartan3E-1600
Microblaze Development Kit) includes ADC and is supposed to do some
digital signal processing of an analog RF signal from 'outside
world'.
How I can input an analog signal to my FPGA?
kclo4
Hi,
I don't know this board do you have a link to it description?
If it is a parallel ADC you generally need to feed your ADC with your
sampling clock and then you get your sample from the adc every clock
cycle. An easy way to check this is to put a probe on the ADC input
using chipscope and put a signal generator at the input of your ADC
and then you look with your probe the signal you receive, if you
inputed a a sin wave you should get a sin wave in the probe.
alexis
Vagant
> using chipscope and put a signal generator at the input of your ADC
> and then you look with your probe the signal you receive, if you
> inputed a a sin wave you should get a sin wave in the probe.
>
> alexis
My problem is that I do not understand how to establish a connection
between an output of signal generator (which is RF connector) and an
input of ADC which is one of FPGA pins as they are physically
incompatible. (As I understand one of FPGA's pins has to be assigned
as an input of FPGA-based ADC.) I just guess that there are should be
something else between an analog source and FPGA board, isn't it? and
I would like to learn what it is.
Frank Buss
> My problem is that I do not understand how to establish a connection
> between an output of signal generator (which is RF connector) and an
> input of ADC which is one of FPGA pins as they are physically
> incompatible.
If the voltage is in the range of the allowed input voltage for your ADC
(take a look at the data sheet of your kit) and the frequency is not too
high (I guess the ADC doesn't convert more than 1 MSPS), try a crocodile
clip. Don't forget to attach the ground, too.
> (As I understand one of FPGA's pins has to be assigned
> as an input of FPGA-based ADC.)
Usually the FPGA doesn't have an integrated ADC, but you have to assign and
program it to access the external ADC.
--
Frank Buss, f...@frank-buss.de
http://www.frank-buss.de, http://www.it4-systems.de
Vagant
> If the voltage is in the range of the allowed input voltage for your ADC
> (take a look at the data sheet of your kit) and the frequency is not too
> high (I guess the ADC doesn't convert more than 1 MSPS), try a crocodile
> clip. Don't forget to attach the ground, too.
Thank you. Using a crocodile clip should work indeed but I look for
something more robust and permanent.
MM
news:63eb6286-cf11-476b...@x35g2000hsb.googlegroups.com...
>
> My problem is that I do not understand how to establish a connection
> between an output of signal generator (which is RF connector) and an
> input of ADC which is one of FPGA pins as they are physically
> incompatible.
What are you talking about? There are no ADCs in Spartan-3E! You can make a
delta-sigma one yourself
(http://www.xilinx.com/support/documentation/ip_documentation/xps_deltasigma_adc.pdf),
but I doubt you can make it run fast enough for any RF application...
Usually an ADC is an external component.
/Mikhail
Andy Peters
Do you have the manual for the board? Hint: it's Xilinx p/n UG257.
The section "Analog Capture Circuit" starts on Page 75 of That Fine
Document.
Header J7, which is a bog standard 0.1"-center pin strip, is the input
to the two ADCs.
You'll probably have to make a cable or adapter so you can use those
pins. If you are incapable of making such an adapter, you probably
shouldn't be messing around with FPGAs.
-a
Vagant
Thank you very much, it's very helpful indeed.
By the way, it's a shame that I have not noticed section 'Analog
Capture Circuit' myself..