Can't transmit from USRP2


#1

Hi,

I while ago we bought two USRP2. When they came we tested them with the
usrp2_siggen and
usrp2_fft programs. Also we had two USRP1 and used USRP_oscope to see
the waveforms produced
by USRP2. Everything seemed to work OK. Then we didn’t do anything with
the USRP2 for a while.
I few days ago I tried using them again and discovered I couldn’t
transmit or receive anything.
I saw in the mailing list that those who got an SD-Card labeled
“9/22/08” must update their
firmware so I updated the firmware using the images from the site. Now I
can receive(?) but
I can’t transmit. I mean no signal is transmited from the USRP2’santenna
because if it where I
would see it in usrp_oscope. Samples however are send from the PC to
USRP2 because the leds on
the Ethernet port light when I run a program like usrp2_siggen or
something of my own.
Does anyone has any idea about what’s wrong? How do I check if the
transmit frequency has been
set OK? In another message it was mentioned that there is no PGA on
USRP2. Then what does
set_gain() in a usrp2 sink or source?

I also noticed something about the received signal. First the noise
variance seems to change when
there is a signal and when there is not. Is this normal? Is there some
AGC circuit that causes this?
If so can I disable it from code. I haven’t noticed anything similar in
USRP1.

Thank you
Manolis


#2

On Mon, Nov 3, 2008 at 4:03 AM, Matigakis E.
removed_email_address@domain.invalid wrote:

…so I updated the firmware using the images from the site.

There is a new firmware image as of this morning, please update to
that. Also, did you update the FPGA code? If not, you’ll need to do
so.

In another message it was mentioned that there is no PGA on USRP2.
Then what does set_gain() in a usrp2 sink or source?

These two functions set the gain on actual daughterboard, if it has a
gain control.

-Johnathan


#3

There is a new firmware image as of this morning, please update to
that. Also, did you update the FPGA code? If not, you’ll need to do
so.

I did update the FPGA bitstream. I am wondering if it could be a
hardware problem.
It seems to me that neither of the two USRP2 we have amplify the signal
that is received
of transmited.
I don’t really believe that it’s probable that two devices malfunction
at the same time.
That is why I got confused with the set_gain() methods.
Has anyone encountered a similar problem when using the USRP2?

Thank you for your help
Manolis


#4

Today I updated gnuradio to current svn9988. And while doing that I also
downloaded the binary package of mb-gcc and built the firmware- files,
successfully thanks to the wiki and a well known search- engine.

The new firmware was loaded onto the sd- card successfully(?) is there
supposed to be some output from u2_flash_tool, I can’t locate the source
for it, so I can’t check for myself. But since I could run find_usrps
with the (probably) new firmware, I guess it went fine.

I then tried all the test- programs, and they ran fine (find_usrps,
tx_sample, … from usrp2/host/apps/), before lunch, but when I got back
from lunch they didn’t.

I simply can’t transmit according to my hardware oscilloscope. Although
I see packages flowing on my eth0- device (using wireshark).

And when I try rx_streaming_samples (with a signal- generator as source,
generating a 100kHz sine) I suddenly receive a lot of noise. Looking at
the fft of the received signal one could say that it might be a
sinusoid in there, but very weak. But only after lunch, before lunch the
received signal was a noise free sinus of 100kHz…

The only thing that is working as expected after I got back is
find_usrps. I think I’ll never eat lunch again :wink:

I’m out of ideas of how to solve this. Suggestions of things to try
and/or check for, no matter how simple would be appreciated.

BR
//Mattias K.


#5

On Fri, Nov 14, 2008 at 7:14 AM, Mattias K. removed_email_address@domain.invalid wrote:

Today I updated gnuradio to current svn9988. And while doing that I also
downloaded the binary package of mb-gcc and built the firmware- files,
successfully thanks to the wiki and a well known search- engine.

You will also need to either build or download the FPGA firmware.

The new firmware was loaded onto the sd- card successfully(?) is there
supposed to be some output from u2_flash_tool, I can’t locate the source for
it, so I can’t check for myself.

There is no output upon success. You can re-run the same command, but
use -v instead of -w to verify the SD card contents match the file you
copied into it.

-Johnathan


#6

Hi Kjellsson,

we had the same problem a while ago and we still haven’t been able to
fix it.
It seems that USRP2 receives but doesn’t amplify the signal so it is
very weak
compared to the noise. We also can’t transmit from the USRP2 at all just
like
you. Have you been able to do something yet?

Manolis.


#7

It looks like you are both using the wrong software. For transmitting,
use usrp2_siggen.py and for receiving use usrp2_fft.py.