Thanks for the advice. I don't think that's my only problem though. My vector
is currently supposed to produce 2500 samples. This combined with an
interpolation factor of 512, should give me 10 msecs of signal. Have I
calculated this correctly? Also, I'm using the gr.modulation block to make the
signal, but if it is producing complex output, does that mean I'm actually
sending 5000 samples?
At the moment, sending my 2500 samples produces an output only 1 msec long.
Regards
Lance
----- Original Message ----
From: Eric Blossom <[EMAIL PROTECTED]>
To: seph 004 <[EMAIL PROTECTED]>
Cc: David Scaperoth <[EMAIL PROTECTED]>; discuss-gnuradio@gnu.org
Sent: Friday, March 2, 2007 7:06:06 PM
Subject: Re: [Discuss-gnuradio] The shortest pulse length
On Fri, Mar 02, 2007 at 12:41:40AM -0800, seph 004 wrote:
> I am only using 1 daughterboard. Sorry about the duc0 = 0
> inclusion. It's something I neglected to remove when I was editing
> the original file. I don't think it should have any effect on what I
> am seeing though. I set the duc frequency to 0 because I wanted to
> transmit at baseband. I've already built the signal I want in the
> gr.vector, I just want the daughterboard to pass it as is. I've
> managed to do that with usrp_siggen.py. By setting the -f option to
> 0 and the -w option to some frequency, I get a waveform of the -w
> frequency at the daughterboard output. I'm pretty sure (0, 0) is
> TXA, and (1, 0) is TXB. My waveform does appear at the TXB output
> when I run the script. The problem is the pulse duration I'm seeing
> is much shorter (about 1/10) than what I expect.
>
> Regards
> Lance
Unless the total number of samples comes out to a multiple of 128,
some will left in the host buffer and not transmitted across the USB.
Try padding your vsource data with zeros to a multiple of 128.
Eric
>
> ----- Original Message ----
> From: David Scaperoth <[EMAIL PROTECTED]>
> To: seph 004 <[EMAIL PROTECTED]>
> Cc: discuss-gnuradio@gnu.org
> Sent: Thursday, March 1, 2007 7:15:36 PM
> Subject: Re: [Discuss-gnuradio] The shortest pulse length
>
>
>
>
> On 3/1/07, seph 004 <[EMAIL PROTECTED]> wrote:
>
>
>
> This is what I did:
>
> def build_graph ():
> nchan = 1
> interp = 512
> duc0 = 0
> duc1 = 0
> fs = 250e3 #2nd sample rate
> between usb and dac
>
> max_dev = 32e3 #1st sample rate divided by 4
> (1st = 2nd sample rate)
> gain = 16e3
> k = 2 * math.pi * max_dev / fs
> vec1 = Numeric.arange (0.624, 0.656, 0.0000128)
>
> vsource = gr.vector_source_f(vec1, False)
> fmmod = gr.frequency_modulator_fc (k)
> amp = gr.multiply_const_cc(gain)
>
> fg = gr.flow_graph ()
>
> u = usrp.sink_c (0, interp, nchan)
>
> tx_subdev_spec = (1, 0) #usrp.pick_tx_subdevice(u)
> m = usrp.determine_tx_mux_value(u, tx_subdev_spec)
> u.set_mux(m)
> subdev = usrp.selected_subdev(u, tx_subdev_spec)
> subdev.set_enable(True)
>
>
> sample_rate = u.dac_freq () / interp
> u.set_tx_freq (0, duc0)
> u.set_tx_freq (1, duc1)
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