On 06/24/2018 04:25 PM, GhostOp14 via USRP-users wrote:
Hi folks,
I have a weird issue I've been attempting to troubleshoot for a bit
and I'm stuck.
So setup:
USRP B205 connected to a Raspberry Pi 3 (so USB 2 mode)
Huawei E3372 USB LTE adapter connected as well
Running the latest Raspbian (stretch)
Problem:
I'm using C++ code to read stream blocks from the device (800,000
samples with the USRP set to 8 MSPS, so basically 1 ms of data).
Without the LTE it works fine, I get only infrequent overruns and the
rest of the logic works fine. As soon as the LTE is plugged in and
the corresponding ethernet interface is up, the recv call can't get a
whole block of data (recv returns 0 bytes). If I ifconfig down the
interface or unplug the LTE it goes back to working just fine. Plug it
back in or ifconfig up the interface, problem returns. Of note, there
is another network connection up on the wifi so the LTE is getting a
lower priority in the routing table and there isn't any data going
across it (I confirmed it with the statistics in ifconfig for that
interface).
So troubleshooting so far:
I'm running the latest UHD code (3.11.1 - Just git pulled the latest
today and rebuilt it).
Works fine on Ubuntu 16.04. No issues with both connected (so it's
not my code :))
There doesn't appear to be any firmware updates to apply to the Huawei
(always worth a shot)
The huawei_cdc_ncm linux driver doesn't appear to have had any updates
in the past couple years (so doesn't look like a linux driver update)
Nothing showing up from dmesg or in /var/log/syslog or
/var/log/messages related to failed recv's.
Made sure there wasn't any data going over the LTE to rule out it's
doing large data transfers
I tested with other USB devices in place of the LTE. Works fine. So
not the port or a general USB issue.
I tried opening the device with num_recv_frames=1024 to see if that
would help, no luck.
I also tried increasing the timeout from the default 0.1 to 0.2 on the
recv call with no luck there either.
Any suggestions?
So, two thoughts:
The rPi USB power supply isn't really up to the task of supply
spec-maximum power to each power. Perhaps your LTE device (combined with
B205) is drawing too much power.
The USB bus bandwidth is *per controller*, and perhaps there just isn't
enough aggregate bandwidth left to service both devices.
The B205 has no external-power input, as I recall, but it's mostly
designed for USB3.0, where the per-port power is higher.
You might try one of those "power booster" USB2.0 "Y" cables, and
plug the "power only" plug into a 5.0V USB power supply.
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