Hi,
I am a new user of USRP/GNU Radio. I am experimenting with a system comprised of one
transmitter and multiple receivers. For now, I have two USRP N200. On
the first USRP, I got one LFTX and one LFRX daughter boards. On the
other, I got one LFRX daughter board.
In my application, it is
important that the transmit and receive channels are synchronized (i.e., both device time and channel phase). For
this, I am using my own GPS and PPS signals.
For the sake of
testing, I am feeding the output of LFTX to all the inputs in LFRX
(i.e., four receive channels). The output/input type is Complexfloat32.
In GRC, when I use a separate USRP source block for each motherboard
(i.e., without synchronization), the system is working and I can receive
four unsynchronised replicas of my transmitted signal.
However, when I a use a single USRP source with two-motherboard and four-channel options, I get the following error message:
linux; GNU C++ version 4.8.2; Boost_105400; UHD_003.007.001-68-gc4b1f810
-- Opening a USRP2/N-Series device...
-- Current recv frame size: 1472 bytes
-- Current send frame size: 1472 bytes
-- Opening a USRP2/N-Series device...
-- Current recv frame size: 1472 bytes
-- Current send frame size: 1472 bytes
-- 1) catch time transition at pps edge
-- 2) set times next pps (synchronously)
Using Volk machine: sse4_a_64_orc
thread[thread-per-block[4]: <block gr uhd usrp source (1)>]: RuntimeError: fifo ctrl timed out looking for acks
>>> Done
My
sample rate is 100e6/128 Hz. In the USRP source I set synch to:
UnknownPPS, Mb0/1 clock source and Mb0/1 time source to EXTERNAL. Mb0/1
subdev spec: A:A A:B. I tried to change the WireFormat from AUTOMATIC
to ComplexInt16 without any difference.
I checked
./test_pps_input and I got a 'success'. I think the issue has to do with
the settings for syncing. Any ideas on what causes this
problem?
Thank you.
Best regards,
Khalid