[USRP-users] USRP B210 time errors with high master clock rate

Perelman, Nathan nperelman at LGSInnovations.com
Wed Oct 25 18:58:46 EDT 2017


I've seen some odd behavior with timestamps for samples from the B210 being
off by large fractions of a second from what I expected when setting the
time to GPS time. I wrote a program (see attached) that uses
get_time_last_pps() to attempt to validate that the time is being set
correctly. I discovered that when using a master clock rate of 61.44 MHz,
the time returned is sometimes off by a quarter second (see output from
running below). At a master clock rate of 16 MHz, I don't see this issue.
Testing was done with UHD 3.10.1.0. Is my program doing something wrong or
is this is an issue with the B200?

 

time_test--args type=b200,master_clock_rate=61.44e6

linux; GNU C++ version 5.2.1 20150902 (Red Hat 5.2.1-2); Boost_106000;
UHD_003.010.001.000-0-unknown

 

 

Creating the usrp device with: type=b200,master_clock_rate=30.72e6...

-- Detected Device: B210

-- Operating over USB 3.

-- Detecting internal GPSDO.... Found an internal GPSDO: GPSTCXO , Firmware
Rev 0.929a

-- Initialize CODEC control...

-- Initialize Radio control...

-- Performing register loopback test... pass

-- Performing register loopback test... pass

-- Performing CODEC loopback test... pass

-- Performing CODEC loopback test... pass

-- Asking for clock rate 61.440000 MHz... 

-- Actually got clock rate 61.440000 MHz.

-- Performing timer loopback test... pass

-- Performing timer loopback test... pass

Using Device: Single USRP:

  Device: B-Series Device

  Mboard 0: B210

  RX Channel: 0

    RX DSP: 0

    RX Dboard: A

    RX Subdev: FE-RX2

  RX Channel: 1

    RX DSP: 1

    RX Dboard: A

    RX Subdev: FE-RX1

  TX Channel: 0

    TX DSP: 0

    TX Dboard: A

    TX Subdev: FE-TX2

  TX Channel: 1

    TX DSP: 1

    TX Dboard: A

    TX Subdev: FE-TX1

 

Time set count 4 check 1/5: ERROR: Time difference at last PPS: 0.249037

Time set count 4 check 4/5: ERROR: Time difference at last PPS: 0.249999

Time set count 8 check 1/5: ERROR: Time difference at last PPS: 0.249999

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