Mux settings

GNU Radio
1

What are the proper mux settings for one DBSRX in RXA and one DBSRX in
RXB? When I used a single DBSRX in RXA 0x00000010 worked well. But now
I want Channel 0 to be RXA, and Channel 1 to be RXB both of which are I
and Q, and not swapped.

So far anything other than 0x32103210 or 0x00000010 produces dirty
output with random-looking noise in the data.

Jared

2

On Mon, Oct 22, 2007 at 05:13:33PM -0400, Jared J. wrote:

What are the proper mux settings for one DBSRX in RXA and one DBSRX
in RXB? When I used a single DBSRX in RXA 0x00000010 worked well.
But now I want Channel 0 to be RXA, and Channel 1 to be RXB both of
which are I and Q, and not swapped.

So far anything other than 0x32103210 or 0x00000010 produces dirty
output with random-looking noise in the data.

Jared

If you’re using a single channel, usrp.determine_rx_mux_value will get
you
the right answer, regardless of the type of daughterboard.

On the DBSRX, 0x00003210 (or for that matter 0x32103210) will set you
up with side A routed to channel 0 and side B routed to channel 1.

See http://gnuradio.org/trac/wiki/UsrpRfxDiagrams
and http://gnuradio.org/doc/doxygen/classusrp__standard__rx.html

Eric

3

Thanks. That means I have issues. :slight_smile: I am trying to use 2 channels,
with a mux setting of 0x32103210. I have a DBSRX on RXA and another one
on RXB. I have no TX. When I do a…

nRead = myDev->read(arr, USB_BUF_SIZE, &bOverrun);

I get perfect data from one channel. (i.e. I_a = arr[0], Q_a = arr[1],
I_a = arr[4], Q_a = arr[5] and so on.) But I get complete junk on the
second channel. (I_a = arr[2], Q_a = arr[3], I_a = arr[6], Q_a =
arr[7]).

I’ve swapped the boards (slot A to slot B and vice versa), and they both
seem to work fine. I’ve run usrp_fft.py -R B and -R A and it works in
both cases, but I can’t find anything to test both at once. But
regardless, I don’t think it’s the USRP’s fault. It think it’s mine
unfortunately. I’m just out of ideas where to look. I’ve been
debugging this for a couple of days now. Ugh. :slight_smile: Any thoughts?

Jared

4

Hello,

I may be having similar problems. I’m using 2 basic RX boards and I
want to
receive four complex signals. I seem to be losing the complex part of
the
first signal. I was using a mux of 0xf3f2f1f0, and after seeing your
message, I tried 0x32103210. Both of them show the same problem with
the
first signal.

I have tried swapping the usrp parts to see if it was a hardware
problem,
but the problem persists.

Thanks for your help,
Hans

----- Original Message -----
From: “Eric B.” [email protected]
To: “Jared J.” [email protected]
Cc: [email protected]
Sent: Monday, October 22, 2007 5:15 PM
Subject: Re: [Discuss-gnuradio] Mux settings…

5

On Mon, Oct 22, 2007 at 05:59:58PM -0700, Hans G. wrote:

Thanks for your help,
Hans

For the Basic Rx, 0xf3f2f1f0 is the correct setting to feed 4 separate
signals into the I inputs of 4 DDCs, with zeros fed to the Q inputs.

To use 4 channels, you must use the std_4rx_0tx.rbf fpga image.
If you use the std_4rx_0tx.rbf image, the decimation rate must be <=
128.
If you need more decimation, you must do it in software.

Eric

6

For the Basic Rx, 0xf3f2f1f0 is the correct setting to feed 4 separate
signals into the I inputs of 4 DDCs, with zeros fed to the Q inputs.

To use 4 channels, you must use the std_4rx_0tx.rbf fpga image.
If you use the std_4rx_0tx.rbf image, the decimation rate must be <= 128.
If you need more decimation, you must do it in software.

Eric

I wasn’t aware that I couldn’t use a decimation of 250. 250 seemed to
work
fine with release 3.0.

Are odd numbers ok? Can I use a decimation of 125?

Thanks,
Hans

7

Hi Eric,

A small question :slight_smile:
Did you mean that 0x00003210 was not different from 0x32103210 on RFX
boards?

Regards,
Tarun
UT Dallas

8

On Tue, Oct 23, 2007 at 08:42:59AM -0700, Hans G. wrote:

I wasn’t aware that I couldn’t use a decimation of 250. 250 seemed to work
fine with release 3.0.

This is the problem that was reported last week. Without the halfband
in the FPGA, the CIC sections aren’t wide enough to support decimation

128 without losing information.

Are odd numbers ok? Can I use a decimation of 125?

With the std_4rx_0tx.rbf image, I believe odd numbers will work.
They will not work with std_2rxhb_2tx.rbf

Thanks,
Hans

Eric

9

On Tue, Oct 23, 2007 at 10:56:09AM -0500, Tarun T. wrote:

Hi Eric,

A small question :slight_smile:
Did you mean that 0x00003210 was not different from 0x32103210 on RFX
boards?

If you’re only using two channels, it doesn’t matter what you route to
the DDC inputs of channels 3 and 4 with this caveat: if you are
routing a zero into any of the Q inputs, you must route a zero into
all of the Q inputs.