Re: [Psrdada-developers] reading .dada file

[Vigneswaran K. <vg....@gm...>]

Dear Andrew,

Thank you for the reply.
I manly had problems in knowing the format of how the data is packed (or
needs to be unpacked) for WSRT.
In the header the following info is stated:
NBIT 8
NDIM 1
NPOL 2
IN_USE 1
BYTES_PER_SECOND 80000000

So i consider that every 8 bits after 4096 bytes is a data sample:
xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx
and every alternate 8 bits taken as it would correspond to a single
polarization.
According to the calculations the file contains 800e6 bytes so 400e6
corresponds to a single polarization, which corresponds to 10 secs worth of
data.
So 40e6 corresponds to 1 sec worth of data also given that BW = 20e6 this
number relates to Fs = 2*BW.

The only consideration that i am not so sure about is that, is the data the
output of a 8 bit ADC (Most significant 8 bits of a 12 bit ADC) and is MSb
the signed bit ?
Also are all the assumptions made above correct ?


Thank you,
Regards


On Fri, Oct 19, 2012 at 1:01 AM, Andrew Jameson <aja...@sw...>wrote:

>  Hi Vigneswaran,
>
>  The PSRDADA .dada format is essentially just a 4096 byte ascii header,
> which you have shown below, followed by packed binary format that
> your instrument produced. So if you were to skip past the first 4KB, you
> should then have access to the raw data. PSRDADA does not make any
> assumptions about the format of this binary data.
>
>  dspsr includes an unpacker that knows how to unpack many instrument
> data formats (including PuMa2). If you know how the binary data is
> packed then you should be able to write the code for your simulator that
> can correctly unpack the data into the format that is convenient for you.
>
>  f you do not, then you might need to look at  the dspsr source code for
> the
>  PuMa2 unpacker to determine how to interpret the binary data.
>
>  Cheers,
>
>  Andrew
>
>  On 19/10/2012, at 4:16 AM, Vigneswaran Karunanithi wrote:
>
> Hi,
>
>  i have a .dada file and following is the contents of the header file
>  HEADER
> DADA HDR_VERSION1.0
> HDR_SIZE  4096
> DADA_VERSION 1.0
> PIC_VERSION1.0
> OBS_ID 11206003
> PRIMARY  unset
> SECONDARY unset
> FILE_NAME /data2/data/06Oct2012_LEAP
> FILE_SIZE 800000000
> FILE_NUMBER 0
> UTC_START 2012-10-06-16:53:40
> MJD_START  56206.7039351851851851852161050249
> OBS_OFFSET 0
> OBS_OVERLAP  0
> SOURCE  B1855+09RA
> 18:57:36.39161
> DEC+09:43:17.2322
> TELESCOPE WSRT
> INSTRUMENT  PuMa2
> FREQ 1406
> BW   20
> TSAMP  0.025
> NBIT 8
> NDIM 1
> NPOL 2
> IN_USE 1
> BYTES_PER_SECOND 80000000
>
>  I want to read the raw data without using dspsr as i would like to read
> the raw data into my simulator.
> can someone help with the format of the .dada file.
>
>  Regards
>
>  --
> ____________________
> Vigneswaran Karunanithi,
> EEMCS TU Delft,
> Zuid-Holland,
> Netherlands,
> Ph: +310623584766
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> Andrew Jameson
> Systems & Software Engineer
> Centre for Astrophysics & Supercomputing
> Swinburne University of Technology
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>
>
>
>


-- 
____________________
Vigneswaran Karunanithi,
EEMCS TU Delft,
Zuid-Holland,
Netherlands,
Ph: +310623584766