Re: [Discuss-gnuradio] GnuRadio: Clock Recovery MM: imu out of bounds

[Tom Rondeau]

On Wed, Aug 19, 2015 at 2:51 AM, Michael B <address@hidden> wrote:

I have created a flowgraph, based on an example of Michael Ossmann, which takes in a signal, and should output bits.

I need to use the clock recovery MM block, which I do not fully understand yet. However, after reading some blogposts, I am quite sure that I can leave most of the settings default, except for the Omega one. Here's my flowgraph:

http://imgur.com/pHRXnZu

When running this flowgraph, it gives me the following error:

thread[thread-per-block[5]:<block clock_recovery_mm_ff (9)>]: mmse_fir_interpolator_ff: imu out of bounds.



While searching, I stumbled upon this piece of code in the source of GnuRadio:


int imu = (int)rint(mu * NSTEPS);  
  if((imu < 0) || (imu > NSTEPS)) {
    throw std::runtime_error("mmse_fir_interpolator_ff: imu out of bounds.\n");
  }

So, I suspect it is not due to my Omega setting (which might be wrong, I have to play with that setting), but that it is due to my Mu setting, which is just the default (0.5). However, I understand that Mu needs to be between 0 and 1, so I do not really understand what the problem is. Anyone who does?

Environment details:

• GNU Radio Companion 3.7.7.1
• Running a GNU Radio live DVD in a virtual machine (VirtualBox 4.2.12) on Windows 7.
• Using Volk machine: ssse3_64

Michael,

I don't have an answer, but I can say where you're doing something wrong. You're samples/symbol (samp_per_sym) is definitely /not/ 2.5k. That's a massively oversampled signal and can't be right. You need to think what's the sampling rate of the system? What's the symbol rate of my signal? That will tell you the samples/symbol you need. It should small, like 2 or 4.

Tom