Hello
I am running the tx_samples_from_file example with the following environment
- USRP B200 connected with USB3.0 to a laptop (12 CPU, 32 GB RAM...)
- Ubuntu 22.04
I just made a small change in the code to set the master clock rate.
Whatever the set of parameters I choose (buffer size with spb, master clock rate), I get an underflow notified by U. More or less frequently depending on the chosen parameters, but always at rate 16e6:
nice -n 18 ./tx_samples_from_file --file my_file --rate 16e6 --freq 75e6 --gain 80 --bw 3e6 --type short --spb 1000000
Creating the usrp device with: ...
[INFO] [UHD] linux; GNU C++ version 11.4.0; Boost_107400; UHD_4.7.0.0-0ubuntu1~jammy1
[INFO] [B200] Detected Device: B200
[INFO] [B200] Operating over USB 3.
[INFO] [B200] Initialize CODEC control...
[INFO] [B200] Initialize Radio control...
[INFO] [B200] Performing register loopback test...
[INFO] [B200] Register loopback test passed
[INFO] [B200] Setting master clock rate selection to 'automatic'.
[INFO] [B200] Asking for clock rate 16.000000 MHz...
[INFO] [B200] Actually got clock rate 16.000000 MHz.
[INFO] [MULTI_USRP] Setting master clock rate selection to 'manual'.
[INFO] [B200] Asking for clock rate 16.000000 MHz...
[INFO] [B200] OK
Using Device: Single USRP:
Device: B-Series Device
Mboard 0: B200
RX Channel: 0
RX DSP: 0
RX Dboard: A
RX Subdev: FE-RX1
TX Channel: 0
TX DSP: 0
TX Dboard: A
TX Subdev: FE-TX1
Setting TX Rate: 16.000000 Msps...
Actual TX Rate: 16.000000 Msps...
Setting TX Freq: 75.000000 MHz...
Setting TX LO Offset: 0.000000 MHz...
Actual TX Freq: 75.000000 MHz...
Setting TX Gain: 80.000000 dB...
Actual TX Gain: 80.000000 dB...
Setting TX Bandwidth: 3.000000 MHz...
Actual TX Bandwidth: 3.000000 MHz...
Checking TX: LO: locked ...
UUU
What do I miss ? I assume there is some kind of ring buffer on the B200 board ? If yes, what is its size ? Can it be changed ? What is the best strategy to avoid underflow ?
Thanks
Arnaud
