Hello!
I am having trouble using a USRP X410 to capture some high-rate data. I would
appreciate any insight or help. Below is a diagram of how our x410 is connected
to our host device.
```
*---------------------* *---------------------*
```
```
| | NIC QSFP Port 0 | | QSFP28 Port 1 | |
```
```
| | ens1f0np0 <>---------------<> sfp1 | |
```
```
| | 192.168.20.1 | | 192.168.20.2 | |
```
```
| |-----------------| |-----------------| |
```
```
| H | NIC QSFP Port 1 | | QSFP28 Port 0 | X |
```
```
| O | ens1f1np1 <>---------------<> sfp0 | 4 |
```
```
| S | 192.168.10.1 | | 192.168.10.2 | 1 |
```
```
| T |-----------------| *-----------* |-----------------| 0 |
```
```
| | Ethernet Port 1 | |Router | | Ethernet Port | |
```
```
| | eno8403 <>-|192.168.1.1|-<> eth0 | |
```
```
| | 192.168.1.20 | | | | 192.168.1.19 | |
```
```
*---------------------* *-----------* *---------------------*
```
When I run $ uhd_find_devices
```
[INFO] [UHD] linux; GNU C++ version 9.4.0; Boost_107100; DPDK_19.11;
UHD_4.6.0.HEAD-0-g50fa3baa
```
```
--------------------------------------------------
```
```
-- UHD Device 0
```
```
--------------------------------------------------
```
```
Device Address:
```
```
serial: [serial number]
```
```
addr: 192.168.20.2
```
```
claimed: False
```
```
fpga: CG_400
```
```
mgmt_addr: 192.168.1.19
```
```
mgmt_addr: 192.168.10.2
```
```
mgmt_addr: 192.168.20.2
```
```
name: [name]
```
```
product: x410
```
```
type: x4xx
```
I am using two images for the FPGA, each of which has different capabilities:
\- UC_200, which on the wiki lists Port 0 as "unused" and can achieve up to 250
Msps per channel.
\- CG_400, which lists both ports on the wiki as "100 GbE" and can achieve up
to 500 Msps per channel.
I am using UHD's C++ API to instruct the x410. My capture process tries to call
"recv" as soon as possible without waiting to write the previous buffer to a
file. The psudocode is as follows:
\- Initialize "circular" buffer of arrays. Each array is "spb" samples long,
and there are N such buffers.
\- Start a "writing" thread that writes data from a queue to a file.
\- Set the number of samples I need (nsamps_requested), set the current number
of samples to 0 (nsamps),
\- set the current buffer index to 0 (buff_idx)
\- set up rx_streamer to start 0.1 seconds in the future and issue
STREAM_MODE_START_CONTINUOUS command.
While (nsamps <= nsamps_requested || not_error)
-Get a pointer to the buffer at buff_idx
-num_rx_samps <- recv(buffer...)
-check metadata returned object
-add the buffer to the queue, increment the buffer index
\- stop streaming
When I use the process above, I can get very long captures using the UC_200
image, with 250 Msps, and by parsing the args
"addr=192.168.20.2,mgmt_addr=192.168.1.19" when creating the multiusrp pointer.
When I switch to the CG_400 image, I can barely record a few seconds worth of
data. I parse the args
"addr=192.168.10.2,second_addr=192.168.20.2,mgmt_addr=192.168.1.19". I changed
the logger level to get a better idea of what might be going on, below are some
outputs for spb at 5000:
```
[DEBUG] [RFNOC::MGMT] Established a route from EPID=4 (SW) to EPID=3
```
```
[DEBUG] [RFNOC::MGMT] Throttling stream endpoint to 100% (0x0)
```
```
[DEBUG] [RFNOC::MGMT] Initiated RX stream setup for EPID=3
```
```
[DEBUG] [RFNOC::MGMT] Finished RX stream setup for EPID=3
```
```
[DEBUG] [0/Radio#0] spp value 2032 exceeds MTU of 8016! Coercing to 1988
```
```
....
```
```
[DEBUG] [RxStreamer#0] Received overrun message on port 0
```
After the last logger message, I catc this in my "check metadata returned
object" step and stop the loop.
When this happens, I sometimes get 0 samples back, and sometimes get less than
the samples per buffer I feed the recv command. I also found that while waiting
for the issued command to take effect, instead of adding empty buffers to my
queue, I check for ERROR_CODE_TIMEOUT and just continue the while loop.
I would imagine if I can handle half the rate at 250 Msps for minutes of
continuous capture, going to 500 Msps I could get more than a couple seconds.
Is this because the UC_200 image has 4GiB of DRAM and the CG_400 doesn't list
any on the wiki? Is there something better I can be doing about the spb (I
tried larger and smaller, with some luck around 50000 spb)? Am I properly
configuring the x410 to use both QSFP28 ports for the CG_400 image?
Thanks!
Zack
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