Re: [Discuss-gnuradio] What is MIMO B?

[Eric Blossom]

On Mon, Dec 11, 2006 at 03:50:59PM +0100, Luis Simoes wrote:
> Hi all,
> 
> I've implemented an application script to cover both ISM bands 433 MHz and 
> 2.4GHz. For that purpose I connect a Flex 2400 (RXA/TXA) and a Flex 400 
> (RXB/TXB) on a USRP Rev 3 motherboard. Everything goes well. But if I connect 
> a USRP rev 4.1 or 4.2 with the same d'board configuration to the USB-Bus, the 
> python script prints out:
> 
> Using RX d'board B: Flex 400 Rx MIMO B
> Using TX d'board B: Flex 400 Tx MIMO B
> 
> The script runs normal but no packet is received and no packet is send (no 
> packet is arriving at another receiver (No Gnuradio receiver).
> If the USRP rev 3 is used the print out is:
>  
> Using RX d'board B: Flex 400 Rx
> Using TX d'board B: Flex 400 Tx
> 
> and packets are received and sent. The print output is obtained by 'print 
> "Using TX d'board %s" % (self.subdev.side_and_name(),)'. Where comes this 
> MIMO B difference comes from? Is this the reason why the application runs 
> with one board and not with the other? How can I solve the problem?

Matt can provide the details.  The difference depends on how the
daughterboard gets its master clock.  The rev4 usrp runs a clock
to the daughterboard that the earlier versions didn't.  That in
combination with how the daughterboard is configured (jumper
positions) gives the difference.

As to why it works on one but not the other I'm not sure.

> Ah, before I forget it. Perhapes this could help you to give me an answer. If 
> I run usrp_fft.py from the examples, I get a 'Failed to tune to initial 
> frequency' in the status bar of the application window. If I try to introduce 
> a frequency, the shell outputs:

That means that the frequency you provided on the command line is out
of the range that the daughterboard can tune.

> ...
> File "/usr/local/lib/python2.4/site-packages/gnuradio/usrp.py", line 184, in 
> tune
>     return tune(self, chan, subdev, target_freq)
>   File "/usr/local/lib/python2.4/site-packages/gnuradio/usrp.py", line 122, 
> in 
> tune
>     ok, baseband_freq = subdev.set_freq(target_freq)
>   File "/usr/local/lib/python2.4/site-packages/gnuradio/db_flexrf.py", line 
> 174, in set_freq
>     R, control, N, actual_freq = self._compute_regs(freq)
>   File "/usr/local/lib/python2.4/site-packages/gnuradio/db_flexrf.py", line 
> 392, in _compute_regs
>     assert self.B_DIV >= self.A_DIV
> AssertionError

Please create a ticket in trac for this.  
  login: guest  
  password: gnuradio

This should be caught in a higher layer, and give a better error message.
The problem is the same: you are asking the daughterboard to tune to a
frequency outside of its range.

Which daughterboard are you using and what is the value that you are
passing to the -f <freq> command line option?

> Please, help me...  I am very grateful for every kind of help
> Thank you guys!

You're welcome!

Eric