Just to save you some debugging time later... you'll want to use FPGA version <= v0.1.2 with OpenBTS and YateBTS.
I still have to spend some time figuring out what changes need to be made to the transceiver code to work with our newer FPGA images. In the FPGA >= v0.2.x we separated some sample counters, which broke some of the transceiver's assumptions about the order in which you could perform "set sample rate" and "enable timestamps" operations.