Re: [Discuss-gnuradio] UHD Source Block and N210/SBX Synchronisation

[Marcus D. Leech]

On 03/01/2016 04:57 AM, Nigel Steed wrote:

Hi All,

 

Has anyone managed to use/modify the UHD Source Block to phase synchronise multiple N210/SBX ?

 

From what I have read I must perform the following

 

(1)    Configure to use external references (10MHz and 1PPS) using the options in the UHD Source Block

(2)    Use integer N mode for the PLL

(3)    Re-tune the frequency of the PLL’s on multiple N210/SBX at the same using a time command

(4)    Align the CORDIC’s at initialisation and after a re-tune from (2) above by stopping and starting a stream disciplined to a time command which issues a reset to the CORDIC’s at the same time

 

Thanks,

 

Nigel

 

The only thing really missing in gr-uhd is the ability to do timed commands.   You can force integer-N mode by constructing your own
  tune_request that includes the integer-N option.  You'd use a feature from the latest Gnu Radio to help you with this, because it involves
  getting into the internal structure of a tune_request blob.   So, use the "Python module" block, and in that Python do something like:

def integer_N_tune_me(freq):
    r = uhd.tune_request(freq)
    r.args = {"mode_n" : "integer"}
    return r

Then, in your UHD source/sink block, instead of using your target frequency directly, use:

your_module_name.integer_N_tune_me(desired_freq)



Martin could probably comment on the feasibility of adding timed commands to gr-uhd.