RX/TX switching

[Fabien PELLET]

Hello again,

I build a flowgraph in C++ with an RX chain and a TX chain. I'm using a 
USRP N210. When I'm in RX, the TX chain is connected to a constant zero 
source and feed a null sink and the RX chain is connected to USRP source 
and sink. When I'm in TX, it is the opposite.

I have to keep the two chains running at the same time for switching 
speed purpose and do not have to stop the flowgraph and restart it. So 
for my switching, I just lock the top block and unlock it after.

If I always stay in RX, I have no underrun. Same thing in TX. My problem 
is that when I lock and unlock the flowgraph, I get a lot of underruns.

As a test, I remove the TX part of my flowgraph and only keep the RX 
part and I try do some lock/unlock sometimes : same problem with underruns.

How to do lock/unlock safely in C++ to avoid underruns ?

Thanks for the help,

Best regards,

Fabien, F4CTZ.