b205mini Rx rate errors

[VSaudray]

Hi,
I work on a b205mini-i using C++ library following the examples sources code. Configuration set and get works well, and acquisition with low rx_rate or with very few samples requested (7Msps or less, or 56Msps and by example less than 30000 total samples requested). But trying rx_rate with higher value and with more or infinite samples request produce uhd::rx_metadata_t::ERROR_CODE_TIMEOUT or uhd::rx_metadata_t::ERROR_CODE_OVERFLOW errors very fast.

The USB3 port used has been tested and is capable of a throughput of at least 300MBps. The over wire data format used is sc16, 1 rx channel, for 14Msps it must be a little more than 56MBps, and for 56Msps a little more than 224MBps. The program does not consume 100% of a CPU core. Currently, the soft run on windows.
So I tested with the examples binaries, rx_samples_to_udp.exe to avoid disk access bottleneck, but obtain similar restrictions.
Here is an example of result with rx_samples_to_udp:

C:\Program Files\UHD\lib\uhd\examples>rx_samples_to_udp.exe --rate 28000000 --nsamps 56000000 --addr 127.0.0.1 --port 7890

Creating the usrp device with: ...
[INFO] [UHD] Win32; Microsoft Visual C++ version 1950; Boost_109000; UHD_4.10.0.0-release
[INFO] [B200] Detected Device: B205mini
[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.
Using Device: Single USRP:
Device: B-Series Device
Mboard 0: B205mini
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 RX Rate: 28.000000 Msps...
[INFO] [B200] Asking for clock rate 28.000000 MHz...
[INFO] [B200] Actually got clock rate 28.000000 MHz.
Actual RX Rate: 28.000000 Msps...

Setting RX Freq: 0.000000 MHz...
Actual RX Freq: 36.000000 MHz...

Setting RX Gain: 0.000000 dB...
Actual RX Gain: 0.000000 dB...

Checking RX: LO: locked ...
Got error code 0x8, exiting loop...

Done!

O

I don't anderstand what is the bottleneck in my setup.

[VSaudray]

Does anyone have any idea what might be causing the problem?
Am I missing something in the b205mini configuration to achieve the desired sampling rate?

[mikiofuku]

Hi.

USB-connected USRPs (such as the USRP B2x0 series) are typically limited to around 20 MSps under Windows.
I'd recommend using Linux instead. You may be able to achieve higher IQ rates under Linux, perhaps up to around 50 MSps.

[VSaudray]

Hi,
Thanks for your response.

So i installed the library uhd (4.8.0) on debian 13.5 on a recent computer.
Currently, i tried with the uhd_rx_cfile binary to test with higher rx rates.
But even at 28MSps, there are some overflow errors.
Here an output sample:

user@PC:~$ uhd_rx_cfile -f 3000000000 -r 28000000 /dev/null
[INFO] [UHD] linux; GNU C++ version 14.2.0; Boost_108300; UHD_4.8.0.0+ds1-2
[INFO] [B200] Loading firmware image: /usr/share/uhd/4.8.0/images/usrp_b200_fw.hex...
[INFO] [B200] Detected Device: B205mini
[INFO] [B200] Loading FPGA image: /usr/share/uhd/4.8.0/images/usrp_b205mini_fpga.bin...
[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] [B200] Asking for clock rate 28.000000 MHz...
[INFO] [B200] Actually got clock rate 28.000000 MHz.
[UHD_RX] Defaulting to mid-point gains:
[UHD_RX] Channel 0 gain: 38.0 dB
Ousrp_source :error: In the last 2577 ms, 2 overflows occurred.
usrp_source :error: In the last 2577 ms, 2 overflows occurred.
Ousrp_source :error: In the last 9567 ms, 1 overflows occurred.
O^C

I'll try other configurations, but if you have an idea, I'll be interested.