[USRP-users] problems with ETTUS B200 and maximum clock rate

massimo zampetti massimo.zampetti at leonardo-si.it
Fri Oct 24 10:29:17 EDT 2014


Hi,
I'm using an ETTUS B200 connected to my PC (USB 3.0 port:***Intel 
Z7**7*, motherboard: *ASRock Z77 Extreme 11*,**OS: *Microsoft Windows 7 
(64 bit)*).

I'm trying to use my SDR with a clock rate of *56 MHz* but it doesn't work.
I  did some tests both with GNURadio and with tx_waveforms.exe.

About tx_waveforms contained in UHD directory, I modified its code to 
add 'usrp->set_master_clock_rate()' and set its argument to 56 MHz.
I set also the argument of 'usrp->set_clock_source()' to 56 MHz. Then I 
run the code.

The result shown on the command prompt is 'UUUU..' (Usrp Underrun).
I obtained the same result with GNURadio.

At the beginning I thought I could set clock rate up to 61.44 Mhz 
(according to the maximum sample rate of DAC: 61.44 MS/s).

I did some tests and here there are the results:

1.
set_master_clock_rate : 56 MHz
set_clock_source: 56 MHz




2.
set_master_clock_rate : 61.44 MHz
set_clock_source: 56 MHz



2.
set_master_clock_rate : 70 MHz
set_clock_source: 56 MHz



Where is the problem? Any suggestions?

Regards,

Massimo
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