Re: [Discuss-gnuradio] FM Receiver

[Almohanad Fayez]

I have run into this problem on the Beagleboard ... here's my explanation for what I think is happening and the fix.  What's happening is GNU Radio is trying to run as a real time thread which if you're root or you've given your Linux username permission to have rtprio privileges but for some reason I also ran into the problem where I can't get realtime scheduling privileges.

The parametes of interest to fix this problem are

cat /proc/sys/kernel/sched_rt_runtime_us
output = 950000

cat /proc/sys/kernel/sched_rt_period_us
output = 1000000

now sched_rt_period_us controls the scheduling period in your processor and sched_rt_runtime_us controls how much of that period is reserved for realtime processing.  When you read the associated driver documentation it says to disable this segmenting for the realtime period partitioning you need to set sched_rt_runtime_us to -1 or you can completely disable this feature in your kernel by "make menuconfig" in your kernel driver directory ... my preference is not to mess with drivers so I set it to -1 with

echo -1 > sched_rt_runtime_us

now when you run
cat /proc/sys/kernel/sched_rt_runtime_us
output = -1

Now you should be able to use realtime scheduling in GNU Radio.  I'm not sure if this is a good fix because it might give background processes realtime privileges which would defeat the purpose of the realtime designation ... for me I'm running console Linux on the Beagleboard so it's an acceptable solution.  As an alternative approach you might try to use the Linux "nice" and "renice" programs to tweak thread priority but I personally wans't successful with this approach.


al fayez

-----Original Message-----
From: Anoth <address@hidden>
To: Discuss-gnuradio <address@hidden>
Sent: Thu, Feb 24, 2011 6:59 pm
Subject: [Discuss-gnuradio] FM Receiver

Hi





I am using an USRP N210 with GNU radio, UHD and GRC on Ubuntu 10.10. I have


connected a WBX daughterboard to the USRP. I want to receive and, of course,


listen the radio thanks to this system. I have built a flow graph and when I


execute it, I only heard noise and can see this message in the terminal :





linux; GNU C++ version 4.4.5; Boost_104200; UHD_002.20110206225409.aea6ac1





>>> gr_fir_fff: using SSE


Current recv sock buff size: 50000000 bytes





Warning:


    error in pthread_setschedparam


    Failed to set thread priority 0.5 (realtime):


    Performance may be negatively affected.


    See the general application notes.





Warning:


    error in pthread_setschedparam


    Failed to set thread priority 0.5 (realtime):


    Performance may be negatively affected.


    See the general application notes.


mboard0 MIMO master





Warning:


    error in pthread_setschedparam


    Failed to set thread priority 0.5 (realtime):


    Performance may be negatively affected.


    See the general application notes.


>>> gr_fir_ccc: using SSE


aUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaU





I have looked on the internet and tried different things but nothing has


changed. Could someone give me an hand to solve with problem ?





Thank you very much,





Francois


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